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Journal Details
Format
Journal
eISSN
2083-134X
First Published
16 Apr 2011
Publication timeframe
4 times per year
Languages
English

Search

Volume 38 (2020): Issue 3 (September 2020)

Journal Details
Format
Journal
eISSN
2083-134X
First Published
16 Apr 2011
Publication timeframe
4 times per year
Languages
English

Search

18 Articles
access type Open Access

TiO2 waveguides thin films prepared by sol-gel method on glass substrates with and without ZnO underlayer

Published Online: 12 Dec 2020
Page range: 381 - 385

Abstract

Abstract

TiO2 thin films have been deposited on glass substrates with and without ZnO underlayer by sol-gel dip coating process. XRD patterns show the formation of anatase phase with the diffraction lines (1 0 1) and (2 0 0) in TiO2/glass sample. In TiO2/(ZnO/glass) sample, TiO2 is composed of anatase phase with the diffraction line (2 0 0) but the diffraction peaks of ZnO wurtzite are also well-defined. The determination of the refractive index and the thickness of the waveguiding layers has been performed by m-lines spectroscopy. The thickness of TiO2 thin films deduced by Rutheford Backscattering Geometry (RBS) agrees well with that obtained by m-lines spectroscopy. TiO2/glass sample exhibits one guided TE0 and TM0 polarized modes. In TiO2/(ZnO/glass) sample, only, TE0 single mode has been excited due to cutoff condition.

Keywords

  • TiO
  • anatase
  • sol-gel
  • waveguides
  • ZnO/glass
access type Open Access

Density functional theory calculations and Hirshfeld surface analysis of propyl-para-hydroxybenzoate (PHB) for optoelectronic application

Published Online: 12 Dec 2020
Page range: 386 - 393

Abstract

Abstract

The geometries, electrostatic potential, Mulliken charge analysis, Natural Bond Orbital analysis and polarizabilities of propyl-para-hydroxybenzoate were calculated using B3LYP functional with 6-311++G(d,p) basis set. The calculated geometries are well matched with the experimental values. The Mullliken atomic charge analysis shows that the eventual charges are contained in the molecule. The NBO analysis explains the intramolecular charge transfer in the PHB molecule. The bonding features of the molecule were analyzed with the aid of Hirshfeld surface analysis. The frontier molecular orbital analysis showed the charge transfer obtained within the molecule. The calculated hyperpolarizability of the PHB molecule was 6.977E −30 esu and it was 8.9 times that of standard urea molecule.

Keywords

  • Density Functional Theory
  • HOMO-LUMO
  • NLO
  • Hirshfeld surface
access type Open Access

A study of nickel and cobalt silicides formed in the Ni/Co/Si(1 0 0) system by thermal annealing

Published Online: 12 Dec 2020
Page range: 394 - 399

Abstract

Abstract

In this work, the Ni/Co/Si system was annealed at temperatures ranging from 300 °C to 800 °C. The samples were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and sheet resistance measurement. The XRD and Raman spectroscopy results showed that the formation of nickel and cobalt silicides (CoSi, Co2Si, Ni2Si, NiSi, NiSi2, CoSi2) is an annealing temperature dependent diffusion process. The diffusion phenomenon was evidenced by RBS. The low values of the sheet resistance which were correlated with the films surface roughness were attributed to the formation of both CoSi and NiSi phases.

Keywords

  • Ni/Co/Si system
  • nickel silicide
  • cobalt silicide
  • XRD
  • RBS
  • Raman spectroscopy
  • AFM
access type Open Access

Some remarks on the paper “Optimization of S:Sn precursor molar concentration on the physical properties of spray deposited single phase Sn2S3 thin films” by J. Srivind, V.S. Nagaretthinam, A.R. Balu [Mater. Sci.-Poland, 34 (2016), 393 – 398]

Published Online: 12 Dec 2020
Page range: 400 - 401

Abstract

Keywords

  • X-ray diffraction
  • thin films
  • errors
  • SnS
access type Open Access

Influence of cation order on the dielectric properties of (1 – x)Pb(Sc0:5Nb0:5)O3-xPb(Yb0:5Nb0:5)O3 ceramics

Published Online: 12 Dec 2020
Page range: 402 - 406

Abstract

Abstract

Ceramic lead niobates and their solid solutions (1 – x)Pb(Sc0:5Nb0:5)O3 – xPb(Yb0:5Nb0:5)O3 were synthesized by solid state reactions from oxides. The structure of investigated samples was characterized by X-ray diffraction (XRD). Dielectric studies of the ceramics were performed by means of broadband dielectric spectroscopy at the temperature ranging from 600 K to 140 K. For all ceramic samples a diffuse phase transition as well as relaxor ferroelectric behavior were observed.

Keywords

  • Pb(ScNb)O
  • solid solution
  • dielectric properties
  • relaxor ferroelectric
access type Open Access

Some remarks on the paper “Influence of zinc concentration on band gap and sub-band gap absorption on ZnO nanocrystalline thin films sol-gel grown” by Munirah, Ziaul Raza Khan, Anver Aziz, Mohd. Shahid Khan, M.U. Khandaker [Mater. Sci-Poland, 35 (1) 2017, 246 – 253]

Published Online: 12 Dec 2020
Page range: 407 - 408

Abstract

Keywords

  • ZnO
  • X-ray diffraction
  • mistakes
access type Open Access

Enhancement of color quality and luminous flux for remote-phosphor LEDs with red-emitting CaMgSi2O6:Eu2+,Mn2+

Published Online: 12 Dec 2020
Page range: 409 - 415

Abstract

Abstract

SiO2 particles and red-emitting CaMgSi2O6:Eu2+,Mn2+ phosphor have been added into a yellow phosphor compound YAG:Ce3+ to enhance the optical efficiency of white light LEDs whose average correlated color temperature (CCT) is in the range of 5600 K ÷ 8500 K. It was observed that altering CaMgSi2O6:Eu2+,Mn2+ concentration from 2 % to 30 % while maintaining 5 % of the SiO2 strongly influenced the color rendering index (CRI), color quality scale (CQS), and lumen efficiency of the compound. Besides, through the application of Monte Carlo simulation and Mie-scattering theory, it was possible to improve the optical properties by CaMgSi2O6:Eu2+,Mn2+ and SiO2 addition. The results provided a practical approach to achieve higher luminous efficiency and better color uniformity in remote-phosphor white LEDs (RP-WLEDs).

Keywords

  • remote-phosphor white LEDs
  • SiO
  • CaMgSiO:Eu
  • Mn
  • color quality scale
  • Mie-scattering theory
access type Open Access

Evaluation of structural, optical and physical properties of polyurethane composites doped with metal alkoxides

Published Online: 12 Dec 2020
Page range: 416 - 423

Abstract

Abstract

In this research, polyurethane (PU)/tetraethyl orthosilicate (TEOS) composite was prepared via one-step polymerization method using different concentrations of TEOS in PU. The structural, optical and physical properties of PU composite were characterized by SEM imaging, FT-IR spectroscopy, water uptake, Raman spectroscopy and optical microscopy imaging of synthesized samples. The SEM results showed that by adding TEOS to the PU, the cell and window size of synthesized samples decreased. This result was also observed in the optical micrographs. The bonding characteristics of PU/TEOS composites were analyzed using Raman and FT-IR spectra. According to the FT-IR spectra, the degree of phase separation (DPS) and hydrogen bonding index, R, in 800 μl TEOS/PU had the highest R and DPS factors. By adding different concentrations of TEOS to PU, the apparent density decreased but the real density increased. The total, open and closed porosity of the synthesized samples were calculated. At low loading of TEOS in PU, the open porosity of the samples increased. The PU/TEOS composites may be promising candidates for absorbing sound.

Keywords

  • polyurethane
  • FT-IR spectroscopy
  • Raman spectroscopy
  • porosity
  • density
  • SEM analysis
access type Open Access

Effect of titanium source and sol-gel TiO2 thin film formation parameters on its morphology and photocatalytic activity

Published Online: 12 Dec 2020
Page range: 424 - 433

Abstract

Abstract

TiO2 thin films with different surface structure have been prepared from alkoxide solutions by the sol-gel method using different cationic precursors and heat treatment techniques. The effect of using titanium isopropoxide as well as titanium butoxide as a titanium source on the surface structure and photocatalytic activity of the resultant thin films was studied. Significant differences in the rate of hydrolysis and condensation reactions during the sol-gel synthesis were observed for these titanium precursors. This had a direct influence on the morphology of the as-prepared TiO2 films. Higher quality oxide coatings were obtained from titanium isopropoxide. They were characterized by a smaller grain size, improved surface roughness and uniform coverage of the glass substrate. A beneficial effect of calcination process after each sol application cycle in contrast to single step calcination after all dip-coating cycles was observed. Photocatalytic degradation tests showed that methyl orange was decolorized in the presence of all prepared TiO2 films by exposing their aqueous solutions to UV light (λ = 254 nm). The highest photocatalytic activity had the TiO2 layer produced using titanium isopropoxide.

Keywords

  • TiO thin film
  • sol-gel
  • photocatalysis
access type Open Access

Semi-organic nonlinear optical material: (((4-sulfonatophenyl)ammonio)oxy)zirconium for dielectric and photonics applications

Published Online: 12 Dec 2020
Page range: 434 - 442

Abstract

Abstract

This article discusses the growth and characterization of (((4-sulfonatophenyl) ammonio)oxy) zirconium (SAOZ) single crystals. Sulphanilic acid incorporated zirconium oxychloride semi-organic single crystals have been synthesized by slow evaporation technique. From the X-ray studies, lattice parameters a = 7.31 Å, b = 7.51 Å, c = 13.92 Å, volume = 765 Å3 have been found and so the crystal has been identified as orthorhombic with non-centrosymmetric space group P212121. The powder XRD examination demonstrated the quality and high crystalline nature of the grown crystal. The presence of functional groups was confirmed by FT-IR technique. The chemical structure of the compound was established by 1H and 13C NMR spectra. The optical transmittance window and the low cutoff wavelength of SAOZ have been identified by UV-Vis-NIR studies. Photoluminescence studies showed a wide blue light emission. TG and DTA examinations were carried out to characterize the thermal behavior of the grown crystal. The mechanical strength of the grown crystal was analyzed by the Vickers microhardness test. The elemental analysis was done by EDAX. The dielectric response of the crystals was analyzed in the frequency range of 50 Hz to 5 MHz at various temperatures and the outcomes were discussed. The SHG efficiency was estimated in correlation with KDP by employing powder Kurtz method.

Keywords

  • slow evaporation
  • SHG efficiency
  • soft material
  • dielectric
  • nonlinear optical
access type Open Access

Preparation and characterization of pH-sensitive hydrogels from photo-crosslinked poly(ethylene glycol) diacrylate incorporating titanium dioxide

Published Online: 12 Dec 2020
Page range: 443 - 449

Abstract

Abstract

The purpose of the present investigation was to prepare pH-sensitive hydrogels from photo-crosslinked poly(ethylene glycol) diacrylate (PEG-DA). Rutile titanium dioxide (TiO2) was employed to modify the PEG-DA hydrogels. The rutile titanium dioxide (TiO2) nanoparticles were prepared by direct oxidation of titanium in the presence of polyethylene glycol (PEG) at high temperature. The nanoparticles were characterized by FT-IR, XRD and SEM. The influence of experimental conditions, such as pH, type and amount of photoinitiators on the release profiles of donepezil hydrochloride (active pharmaceutical ingredient for Alzheimer disease) from modified PEG-DA hydrogels, was investigated. The drug release processes were analyzed kinetically using zero-order, first-order, Hixson-Crowell and Peppas models.

Keywords

  • PEG-DA based hydrogels
  • rutile titanium oxide
  • release profiles
  • kinetic models
access type Open Access

Synthesis, characterization and application of Ru(II) complexes containing pyridil ligands for dye-sensitized solar cells

Published Online: 12 Dec 2020
Page range: 450 - 458

Abstract

Abstract

In this research, a series of Ru(II) complexes, ([Ru(1-7)(ina)(NCS)2] (1-7=5-[6-(5-mercapto-1,3,4-oxadiazol-2-yl)pyridin- 2-yl]-1,3,4-oxadiazole-2-thiol’s, ina=isonicotinic acid) were synthesized and characterized using different spectroscopic and analytic techniques, such as NMR, UV, IR, CV and CHN. Also, the new complexes were used in dye-sensitized solar cells (DSSC) as sensitizers. Current-voltage characteristics showed that the modifications of ligands clearly affected DSSC yield. Additionally, DFT calculations were performed and showed locations of frontier molecular orbitals of the complexes. While the locations of HOMO and HOMO – 1 orbitals are on Ru(II) metal center and SCN ligands, the location of LUMO and LUMO + 1 orbitals are on the 1-7 ligands.

Keywords

  • Ru(II) complexes
  • dye-sensitized solar cells (DSSCs)
  • sensitizer
  • DFT
  • current-voltage characteristics
access type Open Access

Effect of Cd precursor on structure and optical properties of spin coated Zn0:9Cd0:1O films for optoelectronics applications

Published Online: 12 Dec 2020
Page range: 459 - 464

Abstract

Abstract

The development of transparent conducting oxide materials has gained an increased interest in the scientific community for developing efficient low cost optoelectronic devices. The effect of Cd precursor on structural and optical properties of sol-gel synthesized Zn0:9Cd0:1O nanostructured films has been studied by using XRD, AFM, optical absorption and emission spectroscopic techniques. X-ray diffraction confirms the hexagonal wurtzite crystal structure of the deposited films and the relative intensity of diffraction peaks has been observed with different cadmium salts. The granular surface morphology of the synthesized films has been observed from AFM measurements. The optical transmission, band gap and luminescence intensity was found to change for different cadmium salts. These results are very important for developing new materials for optoelectronic applications.

Keywords

  • transparent conducting oxides - TCO
  • thin films
  • sol-gel technique
  • structural properties
  • optical properties
access type Open Access

Subsolidus solution and ionic conductivity of rock-salt structured Li3+5xTa1−xO4 electroceramics

Published Online: 12 Dec 2020
Page range: 465 - 474

Abstract

Abstract

Lithium tantalate solid solution, Li3+5xTa1−xO4 was prepared by conventional solid-state reaction at 925 °C for 48 h. The XRD analysis confirmed that these materials crystallized in a monoclinic symmetry, space group C2/C and Z = 8, which was similar to the reported International Crystal Database (ICDD), No. 98-006-7675. The host structure, β-Li3TaO4 had a rock-salt structure with a cationic order of Li+:Ta5+ = 3:1 over the octahedral sites. A rather narrow subsolidus solution range, i.e. Li3+5xTa1−xO4 (0 ⩽ x ⩽ 0.059) was determined and the formation mechanism was proposed as a replacement of Ta5+ by excessive Li+, i.e. Ta5+ ↔ 5Li+. Both Scherrer and Williamson-Hall (W-H) methods indicated the average crystallite sizes in the range of 31 nm to 51 nm. Two secondary phases, Li4TaO4:5 and LiTaO3 were observed at x = 0.070 and x = −0:013, respectively. These materials were moderate lithium ionic conductors with the highest conductivity of ~2.5 × 10−3 Ω −1 ˙ cm−1 at x = 0, at 0 °C and 850 °C; the activation energies were found in the range of 0.63 eV to 0.68 eV.

Keywords

  • ionic conductivity
  • subsolidus solution
  • β-LiTaO
  • electrical properties
access type Open Access

Comparison of electrical properties of CuO/n-Si contacts with Cu/n-Si

Published Online: 12 Dec 2020
Page range: 475 - 483

Abstract

Abstract

In this study, CuO/n-Si/Al heterojunction contacts were fabricated by thermal evaporation technique. Electrical characteristics of the samples were investigated with the current-voltage (I-V), capacitance-voltage/frequency (C-V/f), and conductancevoltage (G/V) measurements at room temperature. Also, Cu/n-Si/Al Schottky contact was produced as a reference sample to investigate the electrical properties of the samples. The values of ideality factor (n), barrier height ( Φb) and series resistance (Rs) of the samples were calculated from the forward bias current-voltage (I-V) and reverse bias capacitance-voltage (C-V) characteristics. Also, for checking the consistency of the results, Cheung and Norde functions were used. The experimental result values of CuO/n-Si contact were compared with the values of the reference Cu/n-Si Schottky diode. It was observed that the values of the ideality factor and barrier height of the CuO/n-Si heterojunction were higher than those of the Cu/n-Si Schottky contact, while the series resistance was lower. Also, it has been observed that the value of capacitance decreased with increasing frequency and after a certain value of frequency it was almost constant. The ideality factor of CuO/n-Si/Al heterostructure is about 2.40 and so, it is not close to the ideal behavior.

Keywords

  • CuO
  • heterojunction
  • thermal evaporation
  • electrical properties
access type Open Access

The influence of self-doping of stibnite ore with impurities on the preparation, heat capacity, magnetic and transport properties of tetrahedrite Cu12Sb4S13

Published Online: 12 Dec 2020
Page range: 484 - 492

Abstract

Abstract

Stibnite mineral (mainly Sb2S3) has been employed for the synthesis of tetrahedrite Cu12Sb4S13 bulk material by spark plasma sintering. High purity Cu12Sb4S13 can be quickly obtained by two sintering procedures at temperatures from the range of 420 °C to 440 °C for 1 h. Appropriate reduction of Cu content (Cu12+xSb4S13, x ⩽ –0.05) or CuS content (Cu12−ySb4S13−y, y = 0.1 or 0.3) was beneficial to fabricate Cu12Sb4S13. The secondary resintering improved the purity of Cu12Sb4S13 material. The first-order magnetic phase transformation with magnetic hysteresis effect was confirmed by the behavior of susceptibility, heat capacity and resistivity. The magnetization showed a linear increase with increasing field (up to 7 T) and non-saturation behavior was observed. The impurities in stibnite mineral Sb2S3 had a weak influence on the transformation temperature but affected the low-temperature magnetization value (~0.15, close to natural tetrahedrite). Similar transformation was observed by the analysis of heat capacity. The properties such as electrical resistivity, Seebeck coefficient and thermal conductivity were also measured for Cu11:9Sb4S13 and Cu11:9Sb4S12:9. The maximum figure of merit ZT of Cu11:9Sb4S12:9 was 0.22 at 367 K.

Keywords

  • tetrahedrite
  • CuSbS
  • phase transition
  • magnetization
  • heat capacity
access type Open Access

Building superior lighting properties for WLEDs utilizing two-layered remote phosphor configurations

Published Online: 12 Dec 2020
Page range: 493 - 501

Abstract

Abstract

The remote phosphor structure produces higher luminous flux but delivers poorer color quality than the conformal or in-cup phosphor structure. To eliminate this weakness, researchers have attempted to improve the chromatic properties of remote phosphor package. This study tends to enhance lighting features for WLEDs including color quality and luminous flux in general or color rendering index (CRI) and color quality scale (CQS) in particular by applying dual-layer remote phosphor structure. In the simulation section, we utilize two identical LEDs that only differ in correlated color temperature values which are 6600 K and 7700 K. The study offers an idea of placing a yellow-green phosphor layer SrBaSiO4:Eu2+ or a red phosphor layer SrwFxByOz:Eu2+,Sm2+ on the yellow phosphor layer YAG:Ce3+ and then modifying the concentrations of SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ to the suitable values to improve the color quality and lumen output of WLEDs. The results show that red phosphor layer SrwFxByOz:Eu2+,Sm2+ has a significant influence on CRI and CQS improvement. Particularly, the increase of SrwFxByOz:Eu2+,Sm2+ concentration leads to increased CRI and CQS because the red light component increases in WLEDs. On the other hand, the green phosphor layer SrBaSiO4:Eu2+ only brings benefit to the luminous flux. However, the WLEDs’ luminous flux and color quality drop sharply, when SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ concentrations rise extremely, which is verified based on the Mie-scattering theory and the Lambert-Beer law. In short, the article provides general knowledge and primary information for the production of higher-quality WLEDs.

Keywords

  • WLEDs
  • SrBaSiO:Eu
  • SrFBO:Eu
  • Sm
  • luminous efficacy
  • color uniformity
  • Mie-scattering theory
access type Open Access

Rapid sintering of TiB2 ceramics using Co as sintering aid under high pressure condition

Published Online: 12 Dec 2020
Page range: 502 - 507

Abstract

Abstract

The improved TiB2 ceramics were obtained in sintering process at the pressure of 5.5 GPa and temperature of 1550 °C in presence of metallic Co powder. The effect of Co content (ranging from 0 wt.% to 10.0 wt.%) on the phase composition, density, microstructure, Vickers hardness and thermal conductivity of TiB2 ceramics was analyzed. A small amount of new phase Co2B has been created in the reaction of TiB2 and Co. The relative density of sintered TiB2 ceramics reached 98.1 %. When the mass fraction of Co increased, the porosity increased, while the hardness first increased and then decreased. The maximal Vickers hardness values were equal to 33.3 GPa or 28.2 GPa when the used load was of 4.9 N or 9.8 N, respectively. The highest reached value of thermal conductivity was 88.9 W˙m−1 ˙ K−1. The dense TiB2 ceramics with improved hardness and thermal conductivity were ascribed to the high pressure sintering method and Co sintering aid. High pressure sintering method provides a new way for the preparation of ceramics materials.

Keywords

  • titanium diboride
  • cobalt
  • high pressure
  • sintering
18 Articles
access type Open Access

TiO2 waveguides thin films prepared by sol-gel method on glass substrates with and without ZnO underlayer

Published Online: 12 Dec 2020
Page range: 381 - 385

Abstract

Abstract

TiO2 thin films have been deposited on glass substrates with and without ZnO underlayer by sol-gel dip coating process. XRD patterns show the formation of anatase phase with the diffraction lines (1 0 1) and (2 0 0) in TiO2/glass sample. In TiO2/(ZnO/glass) sample, TiO2 is composed of anatase phase with the diffraction line (2 0 0) but the diffraction peaks of ZnO wurtzite are also well-defined. The determination of the refractive index and the thickness of the waveguiding layers has been performed by m-lines spectroscopy. The thickness of TiO2 thin films deduced by Rutheford Backscattering Geometry (RBS) agrees well with that obtained by m-lines spectroscopy. TiO2/glass sample exhibits one guided TE0 and TM0 polarized modes. In TiO2/(ZnO/glass) sample, only, TE0 single mode has been excited due to cutoff condition.

Keywords

  • TiO
  • anatase
  • sol-gel
  • waveguides
  • ZnO/glass
access type Open Access

Density functional theory calculations and Hirshfeld surface analysis of propyl-para-hydroxybenzoate (PHB) for optoelectronic application

Published Online: 12 Dec 2020
Page range: 386 - 393

Abstract

Abstract

The geometries, electrostatic potential, Mulliken charge analysis, Natural Bond Orbital analysis and polarizabilities of propyl-para-hydroxybenzoate were calculated using B3LYP functional with 6-311++G(d,p) basis set. The calculated geometries are well matched with the experimental values. The Mullliken atomic charge analysis shows that the eventual charges are contained in the molecule. The NBO analysis explains the intramolecular charge transfer in the PHB molecule. The bonding features of the molecule were analyzed with the aid of Hirshfeld surface analysis. The frontier molecular orbital analysis showed the charge transfer obtained within the molecule. The calculated hyperpolarizability of the PHB molecule was 6.977E −30 esu and it was 8.9 times that of standard urea molecule.

Keywords

  • Density Functional Theory
  • HOMO-LUMO
  • NLO
  • Hirshfeld surface
access type Open Access

A study of nickel and cobalt silicides formed in the Ni/Co/Si(1 0 0) system by thermal annealing

Published Online: 12 Dec 2020
Page range: 394 - 399

Abstract

Abstract

In this work, the Ni/Co/Si system was annealed at temperatures ranging from 300 °C to 800 °C. The samples were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and sheet resistance measurement. The XRD and Raman spectroscopy results showed that the formation of nickel and cobalt silicides (CoSi, Co2Si, Ni2Si, NiSi, NiSi2, CoSi2) is an annealing temperature dependent diffusion process. The diffusion phenomenon was evidenced by RBS. The low values of the sheet resistance which were correlated with the films surface roughness were attributed to the formation of both CoSi and NiSi phases.

Keywords

  • Ni/Co/Si system
  • nickel silicide
  • cobalt silicide
  • XRD
  • RBS
  • Raman spectroscopy
  • AFM
access type Open Access

Some remarks on the paper “Optimization of S:Sn precursor molar concentration on the physical properties of spray deposited single phase Sn2S3 thin films” by J. Srivind, V.S. Nagaretthinam, A.R. Balu [Mater. Sci.-Poland, 34 (2016), 393 – 398]

Published Online: 12 Dec 2020
Page range: 400 - 401

Abstract

Keywords

  • X-ray diffraction
  • thin films
  • errors
  • SnS
access type Open Access

Influence of cation order on the dielectric properties of (1 – x)Pb(Sc0:5Nb0:5)O3-xPb(Yb0:5Nb0:5)O3 ceramics

Published Online: 12 Dec 2020
Page range: 402 - 406

Abstract

Abstract

Ceramic lead niobates and their solid solutions (1 – x)Pb(Sc0:5Nb0:5)O3 – xPb(Yb0:5Nb0:5)O3 were synthesized by solid state reactions from oxides. The structure of investigated samples was characterized by X-ray diffraction (XRD). Dielectric studies of the ceramics were performed by means of broadband dielectric spectroscopy at the temperature ranging from 600 K to 140 K. For all ceramic samples a diffuse phase transition as well as relaxor ferroelectric behavior were observed.

Keywords

  • Pb(ScNb)O
  • solid solution
  • dielectric properties
  • relaxor ferroelectric
access type Open Access

Some remarks on the paper “Influence of zinc concentration on band gap and sub-band gap absorption on ZnO nanocrystalline thin films sol-gel grown” by Munirah, Ziaul Raza Khan, Anver Aziz, Mohd. Shahid Khan, M.U. Khandaker [Mater. Sci-Poland, 35 (1) 2017, 246 – 253]

Published Online: 12 Dec 2020
Page range: 407 - 408

Abstract

Keywords

  • ZnO
  • X-ray diffraction
  • mistakes
access type Open Access

Enhancement of color quality and luminous flux for remote-phosphor LEDs with red-emitting CaMgSi2O6:Eu2+,Mn2+

Published Online: 12 Dec 2020
Page range: 409 - 415

Abstract

Abstract

SiO2 particles and red-emitting CaMgSi2O6:Eu2+,Mn2+ phosphor have been added into a yellow phosphor compound YAG:Ce3+ to enhance the optical efficiency of white light LEDs whose average correlated color temperature (CCT) is in the range of 5600 K ÷ 8500 K. It was observed that altering CaMgSi2O6:Eu2+,Mn2+ concentration from 2 % to 30 % while maintaining 5 % of the SiO2 strongly influenced the color rendering index (CRI), color quality scale (CQS), and lumen efficiency of the compound. Besides, through the application of Monte Carlo simulation and Mie-scattering theory, it was possible to improve the optical properties by CaMgSi2O6:Eu2+,Mn2+ and SiO2 addition. The results provided a practical approach to achieve higher luminous efficiency and better color uniformity in remote-phosphor white LEDs (RP-WLEDs).

Keywords

  • remote-phosphor white LEDs
  • SiO
  • CaMgSiO:Eu
  • Mn
  • color quality scale
  • Mie-scattering theory
access type Open Access

Evaluation of structural, optical and physical properties of polyurethane composites doped with metal alkoxides

Published Online: 12 Dec 2020
Page range: 416 - 423

Abstract

Abstract

In this research, polyurethane (PU)/tetraethyl orthosilicate (TEOS) composite was prepared via one-step polymerization method using different concentrations of TEOS in PU. The structural, optical and physical properties of PU composite were characterized by SEM imaging, FT-IR spectroscopy, water uptake, Raman spectroscopy and optical microscopy imaging of synthesized samples. The SEM results showed that by adding TEOS to the PU, the cell and window size of synthesized samples decreased. This result was also observed in the optical micrographs. The bonding characteristics of PU/TEOS composites were analyzed using Raman and FT-IR spectra. According to the FT-IR spectra, the degree of phase separation (DPS) and hydrogen bonding index, R, in 800 μl TEOS/PU had the highest R and DPS factors. By adding different concentrations of TEOS to PU, the apparent density decreased but the real density increased. The total, open and closed porosity of the synthesized samples were calculated. At low loading of TEOS in PU, the open porosity of the samples increased. The PU/TEOS composites may be promising candidates for absorbing sound.

Keywords

  • polyurethane
  • FT-IR spectroscopy
  • Raman spectroscopy
  • porosity
  • density
  • SEM analysis
access type Open Access

Effect of titanium source and sol-gel TiO2 thin film formation parameters on its morphology and photocatalytic activity

Published Online: 12 Dec 2020
Page range: 424 - 433

Abstract

Abstract

TiO2 thin films with different surface structure have been prepared from alkoxide solutions by the sol-gel method using different cationic precursors and heat treatment techniques. The effect of using titanium isopropoxide as well as titanium butoxide as a titanium source on the surface structure and photocatalytic activity of the resultant thin films was studied. Significant differences in the rate of hydrolysis and condensation reactions during the sol-gel synthesis were observed for these titanium precursors. This had a direct influence on the morphology of the as-prepared TiO2 films. Higher quality oxide coatings were obtained from titanium isopropoxide. They were characterized by a smaller grain size, improved surface roughness and uniform coverage of the glass substrate. A beneficial effect of calcination process after each sol application cycle in contrast to single step calcination after all dip-coating cycles was observed. Photocatalytic degradation tests showed that methyl orange was decolorized in the presence of all prepared TiO2 films by exposing their aqueous solutions to UV light (λ = 254 nm). The highest photocatalytic activity had the TiO2 layer produced using titanium isopropoxide.

Keywords

  • TiO thin film
  • sol-gel
  • photocatalysis
access type Open Access

Semi-organic nonlinear optical material: (((4-sulfonatophenyl)ammonio)oxy)zirconium for dielectric and photonics applications

Published Online: 12 Dec 2020
Page range: 434 - 442

Abstract

Abstract

This article discusses the growth and characterization of (((4-sulfonatophenyl) ammonio)oxy) zirconium (SAOZ) single crystals. Sulphanilic acid incorporated zirconium oxychloride semi-organic single crystals have been synthesized by slow evaporation technique. From the X-ray studies, lattice parameters a = 7.31 Å, b = 7.51 Å, c = 13.92 Å, volume = 765 Å3 have been found and so the crystal has been identified as orthorhombic with non-centrosymmetric space group P212121. The powder XRD examination demonstrated the quality and high crystalline nature of the grown crystal. The presence of functional groups was confirmed by FT-IR technique. The chemical structure of the compound was established by 1H and 13C NMR spectra. The optical transmittance window and the low cutoff wavelength of SAOZ have been identified by UV-Vis-NIR studies. Photoluminescence studies showed a wide blue light emission. TG and DTA examinations were carried out to characterize the thermal behavior of the grown crystal. The mechanical strength of the grown crystal was analyzed by the Vickers microhardness test. The elemental analysis was done by EDAX. The dielectric response of the crystals was analyzed in the frequency range of 50 Hz to 5 MHz at various temperatures and the outcomes were discussed. The SHG efficiency was estimated in correlation with KDP by employing powder Kurtz method.

Keywords

  • slow evaporation
  • SHG efficiency
  • soft material
  • dielectric
  • nonlinear optical
access type Open Access

Preparation and characterization of pH-sensitive hydrogels from photo-crosslinked poly(ethylene glycol) diacrylate incorporating titanium dioxide

Published Online: 12 Dec 2020
Page range: 443 - 449

Abstract

Abstract

The purpose of the present investigation was to prepare pH-sensitive hydrogels from photo-crosslinked poly(ethylene glycol) diacrylate (PEG-DA). Rutile titanium dioxide (TiO2) was employed to modify the PEG-DA hydrogels. The rutile titanium dioxide (TiO2) nanoparticles were prepared by direct oxidation of titanium in the presence of polyethylene glycol (PEG) at high temperature. The nanoparticles were characterized by FT-IR, XRD and SEM. The influence of experimental conditions, such as pH, type and amount of photoinitiators on the release profiles of donepezil hydrochloride (active pharmaceutical ingredient for Alzheimer disease) from modified PEG-DA hydrogels, was investigated. The drug release processes were analyzed kinetically using zero-order, first-order, Hixson-Crowell and Peppas models.

Keywords

  • PEG-DA based hydrogels
  • rutile titanium oxide
  • release profiles
  • kinetic models
access type Open Access

Synthesis, characterization and application of Ru(II) complexes containing pyridil ligands for dye-sensitized solar cells

Published Online: 12 Dec 2020
Page range: 450 - 458

Abstract

Abstract

In this research, a series of Ru(II) complexes, ([Ru(1-7)(ina)(NCS)2] (1-7=5-[6-(5-mercapto-1,3,4-oxadiazol-2-yl)pyridin- 2-yl]-1,3,4-oxadiazole-2-thiol’s, ina=isonicotinic acid) were synthesized and characterized using different spectroscopic and analytic techniques, such as NMR, UV, IR, CV and CHN. Also, the new complexes were used in dye-sensitized solar cells (DSSC) as sensitizers. Current-voltage characteristics showed that the modifications of ligands clearly affected DSSC yield. Additionally, DFT calculations were performed and showed locations of frontier molecular orbitals of the complexes. While the locations of HOMO and HOMO – 1 orbitals are on Ru(II) metal center and SCN ligands, the location of LUMO and LUMO + 1 orbitals are on the 1-7 ligands.

Keywords

  • Ru(II) complexes
  • dye-sensitized solar cells (DSSCs)
  • sensitizer
  • DFT
  • current-voltage characteristics
access type Open Access

Effect of Cd precursor on structure and optical properties of spin coated Zn0:9Cd0:1O films for optoelectronics applications

Published Online: 12 Dec 2020
Page range: 459 - 464

Abstract

Abstract

The development of transparent conducting oxide materials has gained an increased interest in the scientific community for developing efficient low cost optoelectronic devices. The effect of Cd precursor on structural and optical properties of sol-gel synthesized Zn0:9Cd0:1O nanostructured films has been studied by using XRD, AFM, optical absorption and emission spectroscopic techniques. X-ray diffraction confirms the hexagonal wurtzite crystal structure of the deposited films and the relative intensity of diffraction peaks has been observed with different cadmium salts. The granular surface morphology of the synthesized films has been observed from AFM measurements. The optical transmission, band gap and luminescence intensity was found to change for different cadmium salts. These results are very important for developing new materials for optoelectronic applications.

Keywords

  • transparent conducting oxides - TCO
  • thin films
  • sol-gel technique
  • structural properties
  • optical properties
access type Open Access

Subsolidus solution and ionic conductivity of rock-salt structured Li3+5xTa1−xO4 electroceramics

Published Online: 12 Dec 2020
Page range: 465 - 474

Abstract

Abstract

Lithium tantalate solid solution, Li3+5xTa1−xO4 was prepared by conventional solid-state reaction at 925 °C for 48 h. The XRD analysis confirmed that these materials crystallized in a monoclinic symmetry, space group C2/C and Z = 8, which was similar to the reported International Crystal Database (ICDD), No. 98-006-7675. The host structure, β-Li3TaO4 had a rock-salt structure with a cationic order of Li+:Ta5+ = 3:1 over the octahedral sites. A rather narrow subsolidus solution range, i.e. Li3+5xTa1−xO4 (0 ⩽ x ⩽ 0.059) was determined and the formation mechanism was proposed as a replacement of Ta5+ by excessive Li+, i.e. Ta5+ ↔ 5Li+. Both Scherrer and Williamson-Hall (W-H) methods indicated the average crystallite sizes in the range of 31 nm to 51 nm. Two secondary phases, Li4TaO4:5 and LiTaO3 were observed at x = 0.070 and x = −0:013, respectively. These materials were moderate lithium ionic conductors with the highest conductivity of ~2.5 × 10−3 Ω −1 ˙ cm−1 at x = 0, at 0 °C and 850 °C; the activation energies were found in the range of 0.63 eV to 0.68 eV.

Keywords

  • ionic conductivity
  • subsolidus solution
  • β-LiTaO
  • electrical properties
access type Open Access

Comparison of electrical properties of CuO/n-Si contacts with Cu/n-Si

Published Online: 12 Dec 2020
Page range: 475 - 483

Abstract

Abstract

In this study, CuO/n-Si/Al heterojunction contacts were fabricated by thermal evaporation technique. Electrical characteristics of the samples were investigated with the current-voltage (I-V), capacitance-voltage/frequency (C-V/f), and conductancevoltage (G/V) measurements at room temperature. Also, Cu/n-Si/Al Schottky contact was produced as a reference sample to investigate the electrical properties of the samples. The values of ideality factor (n), barrier height ( Φb) and series resistance (Rs) of the samples were calculated from the forward bias current-voltage (I-V) and reverse bias capacitance-voltage (C-V) characteristics. Also, for checking the consistency of the results, Cheung and Norde functions were used. The experimental result values of CuO/n-Si contact were compared with the values of the reference Cu/n-Si Schottky diode. It was observed that the values of the ideality factor and barrier height of the CuO/n-Si heterojunction were higher than those of the Cu/n-Si Schottky contact, while the series resistance was lower. Also, it has been observed that the value of capacitance decreased with increasing frequency and after a certain value of frequency it was almost constant. The ideality factor of CuO/n-Si/Al heterostructure is about 2.40 and so, it is not close to the ideal behavior.

Keywords

  • CuO
  • heterojunction
  • thermal evaporation
  • electrical properties
access type Open Access

The influence of self-doping of stibnite ore with impurities on the preparation, heat capacity, magnetic and transport properties of tetrahedrite Cu12Sb4S13

Published Online: 12 Dec 2020
Page range: 484 - 492

Abstract

Abstract

Stibnite mineral (mainly Sb2S3) has been employed for the synthesis of tetrahedrite Cu12Sb4S13 bulk material by spark plasma sintering. High purity Cu12Sb4S13 can be quickly obtained by two sintering procedures at temperatures from the range of 420 °C to 440 °C for 1 h. Appropriate reduction of Cu content (Cu12+xSb4S13, x ⩽ –0.05) or CuS content (Cu12−ySb4S13−y, y = 0.1 or 0.3) was beneficial to fabricate Cu12Sb4S13. The secondary resintering improved the purity of Cu12Sb4S13 material. The first-order magnetic phase transformation with magnetic hysteresis effect was confirmed by the behavior of susceptibility, heat capacity and resistivity. The magnetization showed a linear increase with increasing field (up to 7 T) and non-saturation behavior was observed. The impurities in stibnite mineral Sb2S3 had a weak influence on the transformation temperature but affected the low-temperature magnetization value (~0.15, close to natural tetrahedrite). Similar transformation was observed by the analysis of heat capacity. The properties such as electrical resistivity, Seebeck coefficient and thermal conductivity were also measured for Cu11:9Sb4S13 and Cu11:9Sb4S12:9. The maximum figure of merit ZT of Cu11:9Sb4S12:9 was 0.22 at 367 K.

Keywords

  • tetrahedrite
  • CuSbS
  • phase transition
  • magnetization
  • heat capacity
access type Open Access

Building superior lighting properties for WLEDs utilizing two-layered remote phosphor configurations

Published Online: 12 Dec 2020
Page range: 493 - 501

Abstract

Abstract

The remote phosphor structure produces higher luminous flux but delivers poorer color quality than the conformal or in-cup phosphor structure. To eliminate this weakness, researchers have attempted to improve the chromatic properties of remote phosphor package. This study tends to enhance lighting features for WLEDs including color quality and luminous flux in general or color rendering index (CRI) and color quality scale (CQS) in particular by applying dual-layer remote phosphor structure. In the simulation section, we utilize two identical LEDs that only differ in correlated color temperature values which are 6600 K and 7700 K. The study offers an idea of placing a yellow-green phosphor layer SrBaSiO4:Eu2+ or a red phosphor layer SrwFxByOz:Eu2+,Sm2+ on the yellow phosphor layer YAG:Ce3+ and then modifying the concentrations of SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ to the suitable values to improve the color quality and lumen output of WLEDs. The results show that red phosphor layer SrwFxByOz:Eu2+,Sm2+ has a significant influence on CRI and CQS improvement. Particularly, the increase of SrwFxByOz:Eu2+,Sm2+ concentration leads to increased CRI and CQS because the red light component increases in WLEDs. On the other hand, the green phosphor layer SrBaSiO4:Eu2+ only brings benefit to the luminous flux. However, the WLEDs’ luminous flux and color quality drop sharply, when SrwFxByOz:Eu2+,Sm2+ and SrBaSiO4:Eu2+ concentrations rise extremely, which is verified based on the Mie-scattering theory and the Lambert-Beer law. In short, the article provides general knowledge and primary information for the production of higher-quality WLEDs.

Keywords

  • WLEDs
  • SrBaSiO:Eu
  • SrFBO:Eu
  • Sm
  • luminous efficacy
  • color uniformity
  • Mie-scattering theory
access type Open Access

Rapid sintering of TiB2 ceramics using Co as sintering aid under high pressure condition

Published Online: 12 Dec 2020
Page range: 502 - 507

Abstract

Abstract

The improved TiB2 ceramics were obtained in sintering process at the pressure of 5.5 GPa and temperature of 1550 °C in presence of metallic Co powder. The effect of Co content (ranging from 0 wt.% to 10.0 wt.%) on the phase composition, density, microstructure, Vickers hardness and thermal conductivity of TiB2 ceramics was analyzed. A small amount of new phase Co2B has been created in the reaction of TiB2 and Co. The relative density of sintered TiB2 ceramics reached 98.1 %. When the mass fraction of Co increased, the porosity increased, while the hardness first increased and then decreased. The maximal Vickers hardness values were equal to 33.3 GPa or 28.2 GPa when the used load was of 4.9 N or 9.8 N, respectively. The highest reached value of thermal conductivity was 88.9 W˙m−1 ˙ K−1. The dense TiB2 ceramics with improved hardness and thermal conductivity were ascribed to the high pressure sintering method and Co sintering aid. High pressure sintering method provides a new way for the preparation of ceramics materials.

Keywords

  • titanium diboride
  • cobalt
  • high pressure
  • sintering

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