Volume 34 (2016): Issue 1 (March 2016)

The aim of this work was to elaborate two-dimensional behavioral modeling method of thick-film resistors working in low-temperature conditions. The investigated resistors (made from 5 various resistive inks: 10 resistor coupons, each with 36 resistors with various dimensions), were measured automatically in a cryostat system. The low temperature was achieved in a nitrogen-helium continuous-flow cryostat. For nitrogen used as a freezing liquid the minimal temperature possible to achieve was equal to −195.85 °C (77.3 K). Mathematical model in the form of a multiplication of two polynomials was elaborated based on the above mentioned measurements. The first polynomial approximated temperature behavior of the normalized resistance, while the second one described the dependence of resistance on planar resistors dimensions. Special computational procedures for multidimensional approximation purpose were elaborated. It was shown that proper approximation polynomials and sufficiently exact methods of calculations ensure acceptable modeling errors.

Rapid NO₂ gas sensor has been developed based on PbS nanoparticulate thin films synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method at different precursor concentrations. The structural and morphological properties were investigated by means of X-ray diffraction and field emission scanning electron microscope. NO₂ gas sensing properties of PbS thin films deposited at different concentrations were tested. PbS film with 0.25 M precursor concentration showed the highest sensitivity. In order to optimize the operating temperature, the sensitivity of the sensor to 50 ppm NO₂ gas was measured at different operating temperatures, from 50 to 200 ^°C. The gas sensitivity increased with an increase in operating temperature and achieved the maximum value at 150 ^°C, followed by a decrease in sensitivity with further increase of the operating temperature. The sensitivity was about 35 % for 50 ppm NO₂ at 150 ^°C with rapid response time of 6 s. T90 and T10 recovery time was 97 s at this gas concentration.

The molecular modeling of p-nitroanilinium perchlorate molecule was carried out by using B3LYP and HSEH1PBE levels of density functional theory (DFT). The IR and Raman spectra were simulated and the assignments of vibrational modes were performed on the basis of relative contribution of various internal co-ordinates. NBO analysis was performed to demonstrate charge transfer, conjugative interactions and the formation of intramolecular hydrogen bonding interactions within PNAPC. Obtained large dipole moment values showed that PNAPC is a highly polarizable complex, and the charge transfer occurs within PNAPC. Hydrogen bonding and charge transfer interactions were also displayed by small HOMO-LUMO gap and molecular electrostatic potential (MEP) surface. The strong evidences that the material can be used as an efficient nonlinear optical (NLO) material of PNAPC were demonstrated by considerable polarizability and hyperpolarizability values obtained at DFT levels.

Polycrystalline Cr substituted Ni ferrites [NiCr_xFe_2−xO₄ (0.0 ≤ x ≤ 1.0)] were synthesized by conventional ceramic method and sintered at 1350 °C in air. X-ray diffraction (XRD) patterns showing sharp peaks confirmed the formation of single phase cubic spinel structure. The lattice parameters of the samples were determined from the XRD data using Nelson-Riley extrapolation technique. They were found to decrease with increasing Cr concentration obeying Vegard’s law. X-ray density, bulk density and porosity were also calculated from the XRD data. The variation of DC resistivity with temperature was measured by two-probe method. The DC resistivity was found to decrease with increasing temperature indicating the semiconducting nature of the samples. Activation energy was calculated from the Arrhenius plot. AC resistivity, dielectric constant and loss tangent were measured in the frequency range of 1 kHz to 120 MHz at room temperature.

In this study the physico-chemical and catalytic properties of copper bearing MFI zeolites (Cu-MFI) with different Si/Al and Si/Cu ratios were investigated. Two different methods for incorporation of metal ions into the zeolite framework were used: the ion exchange from the solution of copper acetate and the direct hydrothermal synthesis. Direct synthesis of a zeolite in the presence of copper-phosphate complexes was expected to generate more active copper species necessary for the desired reaction than the conventional ion exchange method. Direct decomposition of NO was used as a model reaction, because this reaction still offers a very attractive approach to NO_X removal. The catalytic properties of zeolite samples were studied using techniques, such as XRD, SEM, EPR and nitrogen adsorption/desorption measurements at 77 K. Results of the kinetic investigation revealed that both methods are applicable for the preparation of the catalysts with active sites capable of catalyzing the NO decomposition. It was found out that Cu-MFI zeolites obtained through direct synthesis are promising catalysts for NO decomposition, especially at lower reaction temperatures. The efficiency of the catalysts prepared by both methods is compared and discussed.

Vanadium dioxide VO₂ has been paid in recent years increasing attention because of its various applications, however, its oxidation resistance properties in air atmosphere have rarely been reported. Herein, VO₂(B) nanobelts were transformed into VO₂(A) and VO₂(M) nanobelts by hydrothermal route and calcination treatment, respectively. Then, we comparatively studied the oxidation resistance properties of VO₂(B), VO₂(A) and VO₂(M) nanobelts in air atmosphere by thermo-gravimetric analysis and differential thermal analysis (TGA/DTA). It was found that the nanobelts had good thermal stability and oxidation resistance below 341 °C, 408 °C and 465 °C in air, respectively, indicating that they were stable in air at room temperature. The fierce oxidation of the nanobelts occurred at 426, 507 and 645 °C, respectively. The results showed that the VO₂(M) nanobelts had the best thermal stability and oxidation resistance among the others. Furthermore, the phase transition temperatures and optical switching properties of VO₂(A) and VO₂(M) were studied by differential scanning calorimetry (DSC) and variable temperature infrared spectra. It was found that the VO₂(A) and VO₂(M) nanobelts had outstanding thermochromic character and optical switching properties.

Ca₂Nd₄Ti₆O₂₀, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel) route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21) symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (P_r) and the coercive field (E_c) were about 400 μC/cm² and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF) and activation energy (1.39 eV) of the grain boundary was greater than the capacitance (5.7 pF) and activation energy (1.13 eV) of the grain.

Three methods of AlN layers oxidation: dry, wet and mixed (wet with oxygen) were compared. Some physical parameters of oxidized thin films of aluminum nitride (AlN) layers grown on silicon Si(1 1 1) were investigated by means Energy-Dispersive X-ray Spectroscopy (EDS) and Spectroscopic Ellipsometry (SE). Three series of the thermal oxidations processes were carried out at 1012 °C in pure nitrogen as carrying gas and various gas ambients: (a) dry oxidation with oxygen, (b) wet oxidation with water steam and (c) mixed atmosphere with various process times. All the research methods have shown that along with the rising of the oxidation time, AlN layer across the aluminum oxide nitride transforms to aluminum oxide. The mixed oxidation was a faster method than the dry or wet ones.

Nanostructured barium doped bismuth ferrite, Bi₀.₈Ba₀.₂FeO₃ porous ceramics with a relatively high magnetic coercivity was fabricated via sacrificial pore former method. X-ray diffraction results showed that 20 wt.% Ba doping induces a structural phase transition from rhombohedral to distorted pseudo-cubic structure in the final porous samples. Moreover, utilizing Bi₀.₈Ba₀.₂FeO₃ as the starting powder reduces the destructive interactions between the matrix phase and pore former, leading to an increase in stability of bismuth ferrite phase in the final porous ceramics. Urea-derived Bi₀.₈Ba₀.₂FeO₃ porous ceramic exhibits density of 4.74 g/cm³ and porosity of 45 % owing the uniform distribution of interconnected pores with a mean pore size of 7.5 μm. Well defined nanostructured cell walls with a mean grain size of 90 nm were observed in the above sample, which is in a good accordance with the grain size obtained from BET measurements. Saturation magnetization decreased from 2.31 in the Bi₀.₈Ba₀.₂FeO₃ compact sample to 1.85 A m²/kg in urea-derived Bi₀.₈Ba₀.₂FeO₃ porous sample; moreover, coercivity increased from 284 to 380 kA/m.

Cu–Sn–Fe alloys with different compositions were developed by casting, normalizing treatment, cold roll and subsequent annealing treatment. The results showed that the tensile strength and resistivity of the Cu–xSn–xFe alloys (where x represents wt.%) improved with increasing the content of Sn and Fe. Compared with the as-cast alloys, the resistivity and tensile strength of the Cu–xSn–xFe alloys after normalizing and cold rolling treatment increased. In addition, the resistivity and mechanical properties of the alloys after the annealing treatment were improved significantly. Finally, a conclusion could be drawn that the annealed Cu–2Sn–5Fe alloy had good mechanical properties and resistivity, and the values of the tensile strength, mechanical elongation and resistivity reached 552 MPa, 32 % and 1.92 μΩ cm, respectively.

The aim of the present paper has been to verify the effectiveness and usefulness of a novel deposition process named GIMS (Gas Injection Magnetron Sputtering) used for the flrst time for deposition of Ti/TiO₂ coatings on large area glass Substrates covered in the condition of industrial scale production. The Ti/TiO₂ coatings were deposited in an industrial System utilizing a set of linear magnetrons with the length of 2400 mm each for covering the 2000 × 3000 mm glasses. Taking into account the speciflc course of the GIMS (multipoint gas injection along the magnetron length) and the scale of the industrial facility, the optical coating uniformity was the most important goal to check. The experiments on Ti/TiO₂ coatings deposited by the use of GIMS were conducted on Substrates in the form of glass plates located at the key points along the magnetrons and intentionally non-heated during any stage of the process. Measurements of the coatings properties showed that the thickness and optical uniformity of the 150 nm thick coatings deposited by GIMS in the industrial facility (the thickness differences on the large plates with 2000 mm width did not exceed 20 nm) is fully acceptable form the point of view of expected applications e.g. for architectural glazing.

In this research polyimide films were prepared by physical vapor deposition (PVD), using solid state reaction of pyromellitic dianhydride (PMDA) and p-phenylene diamine (PDA) to form poly(amic acid) (PAA) films. The resultant films were converted to polyimide by thermal treatment, usually below 300 °C. For this study, a FT-IR spectrometer has been used to measure the effect of imidization temperature on the chemical structure of the vapor-deposited thin films of aromatic PI. When temperature increased, an increase in all absorption peaks was observed. This suggests that residual PAA monomers continued to be converted into PI. The surface topology of the PI films obtained at imidization temperatures of 150, 200, 250 °C for 1 hour was further examined by using AFM atomic force microscopy. It can be clearly seen that the surface became rougher with increasing imidization temperature. The thermal stability of polyimide was also studied by using thermogravimetric analysis (TGA).

This work presents the very first results of the application of plasma magnetic filtering achieved by a coil coupled with an electrical circuit of a coaxial accelerator during the synthesis of A1N thin films by use of Impulse Plasma Deposition method (IPD). The uniqueness of this technical solution lies in the fact that the filter is not supplied, controlled and synchronized from any external device. Our solution uses the energy from the electrical circuit of plasma accelerator. The plasma state was described on the basis of OES studies. Estimation of the effects of plasma filtering on the film quality was carried out on the basis of characterization of structure morphology (SEM), phase and chemical composition (vibrational spectroscopy). Our work has shown that the use of the developed magnetic self-filter improved the structure of the AlN coatings synthesized under the condition of impulse plasma, especially by the minimization of the tendency to deposit metallic aluminum droplets and columnar growth.

The structural, electronic and optical properties of (BeTe)_n/(ZnSe)_m superlattices have been computationally evaluated for different configurations with m = n and m≠n using the full-potential linear muffin-tin method. The exchange and correlation potentials are treated by the local density approximation (LDA). The ground state properties of (BeTe)_n/(ZnSe)_m binary compounds are determined and compared with the available data. It is found that the superlattice band gaps vary depending on the layers used. The optical constants, including the dielectric function ε(ω), the refractive index n(ω) and the refractivity R(ω), are calculated for radiation energies up to 35 eV.

In this paper, the impact of partial substitution of calcium for barium in (Ba_1-xCa_x) (M_0.9Y_0.1) O₃, M = Ce, Zr on physicochemical properties of the powders and sintered samples was investigated. The powders, with various contents of calcium (x = 0, 0.02, 0.05, 0.1), were prepared by means of thermal decomposition of organometallic precursors containing EDTA. All of the BaCeO₃-based powders synthesised at 1100 °C were monophasic with a rhombohedral structure, however, completely cubic BaZrO₃-based solid solutions were obtained at 1200 °C. A study of the sinterability of BaZr_0.9Y_0.1O₃ and BaCe_0.9Y_0.1O₃-based pellets was performed under non-isothermal conditions within a temperature range of 25 to 1200 °C. The partial substitution of barium for calcium in the (Ba_1-xCa_x) (M_0.9Y_0.1) O₃, M = Ce, Zr solid solution improved the sinterability of the samples in comparison to the initial BaCe_0.9Y_0.1O₃ or BaZr_0.9Y_0.1O₃. The relative density of calcium-modified BaCe_0.9Y_0.1O₃-based samples reached approximately 95 to 97 % after sintering at 1500 °C for 2 h in air. The same level of relative density was achieved after sintering calcium-modified BaZr_0.9Y_0.1O₃ at 1600 °C for 2 h. Analysis of the electrical conductivity from both series of investigated materials showed that the highest ionic conductivity, in air and wet 5 % H₂ in Ar, was attained for the compositions of x = 0.02 to 0.05 (Ba_1-xCa_x)(M_0.9Y_0.1)O₃, M = Zr, Ce. The oxygen reduction reaction on the interface Pt│BaM0.9Y0.1O3, M = Ce, Zr was investigated using Pt microelectrodes. Selected samples of (Ba_1-xCa_x) (M_0.9Y_0.1)O₃, M = Zr, Ce were tested as ceramic electrolytes in hydrogen-oxygen solid oxide fuel cells operating at temperatures of 700 to 850 °C.

The improvement of optical confinement on the back crystalline silicon solar cell is one of the factors leading to its better performance. Porous silicon (PS) layer can be used as a back reflector (BR) in solar cells. In this work, single layers of porous silicon were grown by electrodeposition on a single crystalline silicon substrate. The measurement of the total reflectivity (R_T) on Si/PS surface showed a significant improvement in optical confinement compared to that measured on Si/standard Al back surface field (BSF). The internal reflectivity (R_B) extracted from total reflectivity measurements achieved 86 % for the optimized single PS layer (92 nm thick layer with 60 % porosity) in the wavelength range between 950 and 1200 nm. This improvement was estimated as more than 17 % compared to that measured on the surface of Si/BSF Al contact. To improve the stability and passivation properties of PS layer BR, silicon nitride layer (SiN_x) was deposited by PECVD on a PS layer. The maximum measured total reflectivity for PS/SiNx achieved approximately 56 % corresponding to an improved R_B of up to 83 %. The PS formation process in combination with the PECVD SiN_x, can be applied in the photovoltaic cell technology and offer a promising technique to produce high-efficiency and low-cost c-Si solar cells.

We investigated the structural stability as well as the mechanical, electronic and magnetic properties of the Full-Heusler alloy CoNiMnSi using the full-potential linearized augmented plane wave (FP-LAPW) method. Two generalized gradient approximations (GGA and GGA + U) were used to treat the exchange-correlation energy functional. The ground state properties of CoNiMnSi including the lattice parameter and bulk modulus were calculated. The elastic constants (C_ij) and their related elastic moduli as well as the thermodynamic properties for CoNiMnSi have been calculated for the first time. The existence of half-metallic ferromagnetism (HM-FM) in this material is apparent from its band structure. Our results classify CoNiMnSi as a new HM-FM material with high spin polarization suitable for spintronic applications.

Ag nanoparticles (NPs) encapsulated by polycarbazole (PCz) have been synthesized using ion adsorption method. The PCz synthesis around Ag NPs has been performed by adsorbing Ag⁺¹ and Fe⁺³ oxidants onto Ag NPs, which initiated surface polymerization and thus, Ag NPs@PCz nanocomposite has been synthesized. The morphology of pure NPs and composite NPs was characterized by TEM which also elucidated the effect of oxidant on the core NPs, beside their morphologies and phase contrasts of metal NPs and polymer. The polymer around the surface of core NPs was characterized by FT-IR which proved that PCz was the organic phase of the composite NPs. UV-Vis spectroscopy has been employed to study surface plasmon resonance (SPR) of pure NPs and composite of NP which demonstrated that SPR of core NPs remained preserved after coating with the polymer. Furthermore, Zeta Sizer Nano series has been applied to analyze the dispersion behavior of pure NPs and composite NPs which displayed the greatly improved dispersion behavior of the composite NPs as compared to pure Ag NPs. Therefore, our study proved helpful to analyze the suitability of metal oxidants for PCz based nanocomposite synthesis and determination of their optical and dispersion behavior.

Al and Cu doped ZnO nanoparticles are considered as appropriate for modulation of structural and optoelectronic properties. Al atoms are found to substitute the host Zn whereas Cu dopants mainly segregate in grain boundaries and thereby determine the optical properties. The undoped as well as Al and Cu doped ZnO exhibit spherical well defined particles. The spherical nanoparticles change to rod type structures on co-doping. The average particle size decreases on doping what consequently results in an increment in band gap. Blue shift in UV absorption is governed by the functional group of glucose; further blue shift occurring on metal doping may be attributed to Burstein-Moss effect. PL spectra of doped and undoped ZnO show a dominant near band gap UV emission along with visible emission owing to the defects. The PL peak intensity increases on doping with Cu and Al. The linear I-V characteristics indicate the ohmic behavior of ZnO nanostructures.

In this research work, nanocrystalline BST (Ba_0.6Sr_0.4TiO₃) powders were synthesized through a modified sol-gel process, using barium acetate, strontium acetate and titanium isopropoxide as the precursors. In this process, stoichiometric proportions of barium acetate and strontium acetate were dissolved in acetic acid and titanium (IV) isopropoxide was added to form BST gel. The as-formed gel was dried at 200 °C and then calcined in the temperature range of 600 to 850 °C for crystallization. The samples were characterized by infrared spectroscopy method (FT-IR), X-ray diffraction technique (XRD) and field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy. EDS analysis of these samples confirmed the formation of the final phase with the special stoichiometry. The formation of a cubic perovskite crystalline phase with nanoscale dimension was detected using the mentioned techniques. The results showed that the obtained crystallite sizes were 33 and 37 nm for BST powder calcined at 750 and 850 °C, respectively.

ZrO₂ and a series of NiO/ZrO₂ hydrogels (5 to 25 wt.% NiO) were co-precipitated with the aid of NaOH–Na₂C₂O₄ solution. Two fluorinated hydrogels were also prepared by wet impregnation method. The samples were calcined in the temperature range of 550 to 850 °C. The surface properties of the samples were determined using DTA, XRD and nitrogen adsorption at −196 °C. The conversion of isopropanol was tested using microcatalytic pulse technique. DTA measurements showed that the addition of nickel oxide to zirconia influences the phase transition of ZrO₂. XRD revealed that the tetragonal phase was formed at T ⩽ 650 °C, while a biphasic mixture was obtained at T ⩾ 750 °C. No spinel structure was detected by both DTA and XRD techniques and only traces of cubic NiO were detected for the samples containing ⩾ 15 wt.% nickel oxide and calcined at T ⩾ 750 °C. Significant changes in texture, surface acidity and catalytic activity were found as a result of the effects of thermal treatment and chemical composition. Incorporation of fluoride ions greatly increased the surface acidity and consequently enhanced the dehydration activity. It has been found that dehydration activity is related to the amount of surface acidity while the dehydrogenation of this alcohol is sensitive to NiO content.

In the present paper structural and electronic properties of rare earth pnictides have been presented. The present calculation has been performed using self-consistent tight binding linear muffin tin orbital (TB-LMTO) method within the local density approximation (LDA). The studied compounds undergo a structural phase transition from NaCl-type structure to CsCl-type structure. The electronic band structure and density of states of the pnictides have been reported. The equilibrium lattice parameter a (Å), bulk modulus B (GPa), number of f-states at the Fermi level N_f (states/Ry cell) and volume collapse of AmBi and CmBi have also been reported. The calculated equilibrium structural parameters are in good agreement with the available experimental results.

The electronic and optical properties of Mn–S co-doped anatase TiO₂ were calculated using the plane-wave-based ultrasoft pseudopotential density functional method within its generalized gradient approximation (GGA). The calculated results show that the band gap of Mn–S co-doped TiO₂ is larger than that of the pure TiO₂, and two impurity bands appear in the forbidden band, one of which above the valence band plays a vital role for the improvement of the visible light catalytic activity. The Mn–S co-doped anatase TiO₂ could be a potential candidate for a photo catalyst because of its enhanced absorption ability of visible light.

Recent advances in general medicine led to the development of biomaterials. Implant material should be characterized by a high biocompatibility to the tissue and appropriate functionality, i.e. to have high mechanical and electrical strength and be stable in an electrolyte environment – these are the most important properties of bioceramic materials. Considerations of biomaterials design embrace also electrical properties occurring on the implant-body fluid interface and consequently the electrokinetic potential, which can be altered by modifying the surface of the implant. In this work, the surface of the implants was modified to decrease the risk of infection by using metal colloids. Nanocolloids were obtained using different chemical and electrical methods. It was found that the colloids obtained by physical and electrical methods are more stable than colloids obtained by chemical route. In this work the surface of modified corundum implants was investigated. The implant modified by nanosilver, obtained by electrical method was selected. The in vivo research on animals was carried out. Clinical observations showed that the implants with modified surface could be applied to wounds caused by atherosclerotic skeleton, for curing the chronic and bacterial inflammations as well as for skeletal reconstruction surgery.

Thermal properties of Cu–Zn partially substituted Bi_1.8Sr₂Ca₂Cu_3.2-xZn_xO_10+δ (x = 0, 0.1 and 0.5) glass-ceramic systems have been investigated with the help of a differential thermal analyzer (DTA) by using Johnson-Mehl-Avrami-Kolmogorov (JMAK) approximation. Non-isothermal crystallization kinetics of the samples has been tested. The calculated values of activation energy of crystallization (E) and Avrami parameter (n) ranged between 306.1 and 338.3 kJ.mol^-1 and 1.29 and 3.59, respectively. Crystallization kinetics was compared following the partial substitution, before and after Zn doping of the sample. In addition, by using a scanning electron microscope (SEM) and X-ray powder diffractometer (XRD), structural properties of Zn doped BSCCO glass-ceramic samples were determined. Surface morphology of the samples was studied by SEM measurements. Lattice parameters and volume of the samples were calculated from the XRD measurements.

M-type strontium ferrite with compositions SrFe_(12-2x)Co_xTi_xO₁₉ (x = 0.0, 0.3, 0.5, 0.7, 1.0), were prepared by two route ceramic method. The effects of Co–Ti substitution on their microstructure, electromagnetic properties, and microwave absorptive behavior were analyzed. The complex permittivity (∊′-j∊″) and complex permeability (μ′-jμ″) have been measured from 8.2 to 12.4 GHz using a network analyzer. Scanning electron microscope was used to analyze the grain size distribution and porosity of the ferrite. X-ray diffraction confirmed the M-type structure of the doped strontium ferrite. Vibrating sample magnetometer was used to study hysteresis loop of the ferrite. This study suggests that the control of grain size, decrease in coercivity and enhanced values of dielectric constant and loss are effective means to improve microwave absorption. The dielectric constant and loss were enhanced in comparison to the permeability constant and loss over the entire frequency range.

The mechanical properties of silicate glass-ceramics were evaluated based on the compressive strength tests. It was found that Ta₂O₅ addition improved densification, refinement of the microstructure and toughening of the bodies. The maximum compressive strength of the bodies with 1 mol% Ta₂O₅ was increased 3-fold (245.92 ±0.3 MPa) in comparison to undoped glass-ceramics which was measured to be 89.04 ±0.3 MPa, while for 3 mol% it became 4-fold (387.12 ±0.4 MPa) greater. The addition of Ta₂O₅ stabilized the system by controlling the biodegradation of the glass-ceramics. It effectively depressed the apatite formation as by addition of 3 mol% Ta₂O₅ no apatite layer was observed. It may be concluded from this study that mechanical and physical properties can be improved by the addition of Ta₂O₅, but at a cost of bioactivity. Still the optimized composition having Ta₂O₅ ⩽ 1 mol% may provide appropriate strength of biomaterials for high load bearing applications.

Samples obtained by nitriding of promoted nanocrystalline iron and the nitrides reduction at various nitriding potential in terms of thermodynamic parameters were investigated by electron paramagnetic resonance/ferromagnetic resonance (EPR/FMR) method at room temperature. Experimental FMR spectra were fitted by the Dysonian-type resonance lines arising from the presence of different Fe–N phases. The obtained FMR parameters allowed us to identify the component phases and to determine their magnetic properties. In general, the proposed simple method of decomposition of the FMR spectra produced results on the phase content in investigated samples that were consistent with XRD measurements and additionally, magnetic characteristics of the studied nanomagnets.

SrLa₄Ti_5−xSn_xO₁₇ (0 ≤ x ≤ 2) ceramics were fabricated through solid state ceramic route and their microwave dielectric properties were investigated in an attempt to tune their temperature coefficient of resonant frequency (τ_f) to zero. The compositions were sintered to single phase SrLa₄Ti₅O₁₇ and SrLa₄Ti_4.5Sn_0.5O₁₇ ceramics at x = 0 and x = 0.5, and SrLa₄Ti_4−xSn_xO₁₇ along with a small amount of La₂Ti₂O₇ at x = 1. The major phase observed at x = 2 was La₂Ti₂O₇ but along with SrLa₄Ti₄SnO₁₇ and SrLa₄Ti₄O₁₅ as the secondary phases. τ_f decreased from 117 to 23.0 ppm/°C but at the cost of dielectric constant (ε_r) and quality factor multiplied by resonant frequency (Q_uf_o) which decreased from 65 to 33.6 and 11150 to 4191 GHz, respectively. The optimum microwave dielectric properties, i.e. τ_f = 38.6 ppm/°C, ε_r = 45.5 and Q_uf_o = 7919 GHz, correspond to the SrLa₄Ti_5−xSn_xO₁₇ composition with x = 1.