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In this work, the concentration dependencies of unit cell parameters, microstructure, dielectric, impedance spectra, and magnetic properties of (1 – x)SmFeO3–xNaNbO3 were studied for the first time. It was found that at a concentration x = 0.7, the unit cell parameter a, the tilt angles θ and rotation angles φ of oxygen octahedra and the bond lengths Fe-O1 and Fe-O3 of samarium ferrite SmFeO3 (SFO) have a maximum, and Fe-O2 has a minimum value. The tilt angle θ, rotation angle φ of the octahedral, and the bond lengths of sodium niobate NaNbO3 (NNbO) change nonmonotonically. For x = 0.9, the unit cell parameters b and c, as well as all bond lengths in the NaO9 tetradecahedra, reach their minimum values. Anomalies corresponding to the spin-reorientation transition temperatures TSR1 and TSR2 were detected in the dielectric spectra of SFO at temperatures of 200 and 309 °C. The jump in the real part of the dielectric constant ε′(T), starting before – 100 °C, is attributed to the response of the dipole moments to the magnetic moment jump and spin switching (TSSW). Anomalies corresponding to transitions between different phases in this antiferroelectric were found in the temperature dependences of ε′(T) and dielectric loss tangent tgδ(T) of NNbO at temperatures of – 75, 23, 160, 278, 379, and 433 °C. From magnetic measurements, it was found that the composition with x = 0.8 has a minimum size of coherent scattering regions of D = 94 nm, representing the second critical size at which the coercive field Hc reaches its maximum value. [ABSTRACT FROM AUTHOR]

Utilizing reactive DC magnetron sputtering method, TiN coatings were deposited on the silicon substrates at different nitrogen flows and powers. A study of the X-ray phase composition of the coatings was carried out. The stoichiometric composition of the coatings was determined using energy dispersive x-ray spectroscopy. The structure of the surface, cross-section, and thickness of the coatings were determined using scanning electron (SEM) and atomic force microscopy (AFM). A significant change in the surface structure of TiN coatings was established with changes in deposition power and nitrogen flow. SEM images of cross-sections of all coated samples showed that the formation of coatings occurs in the form of a columnar structure with a perpendicular orientation relative to the silicon substrate. The mechanical properties (elastic modulus E and microhardness H) of TiN coatings of the first group demonstrate a maximum at a nitrogen flow of 3 sccm and are 184 ± 11 GPa and 15.7 ± 1.3 GPa, respectively. In the second group, the values of E and H increase due to a decrease in the size of the structural elements of the coating (grains and crystallites). In the third group, E and H decrease. Microtribological tests were carried out in 4 stages: at a constant load, multi-cycle for 10 and 100 cycles, and with increasing load. The coefficient of friction (CoF) and specific volumetric wear ω depend on the roughness, topology, and mechanical properties of the resulting coatings. Fracture toughness was determined using nanoscratch and depends on the mechanical properties of TiN coatings. Within each group, coatings with the best mechanical and microtribological properties were described: in the first group—TiN coating at 3 sccm (with (29.6 ± 0.1) at.% N), in the second group—TiN coating at 2 sccm (with (40.8 ± 0.2) at.% N), and in the third group—TiN coating at 1 sccm (c (37.3 ± 0.2) at.% N). [ABSTRACT FROM AUTHOR]

The xBiFeO3–(1–x)PbZr0.9Ti0.1O3 composites synthesized by the solid-phase reaction were characterized using complex methods to determine their structure and physical properties. According to the results of X-ray diffraction analysis, it was found that the synthesized composites have a rhombohedral perovskite structure with the space symmetry group R3с, and there are no impurities or second phases present in either the ferrite or ferroelectric phases. According to the results of impedance spectroscopy, it was found that the nature of the relaxation in the composites is non-Debye, suggesting a complex conduction mechanism involving multiple relaxation processes. With an increasing proportion of ferroelectric PbZr0.9Ti0.1O3 (PZT) phase, the composites exhibit dual-arc behavior in the Cole-Cole diagrams obtained from the impedance spectroscopy measurements. The dual-arc behavior shows the contribution of both the bulk (grain) and grain boundary to the conduction mechanism in the temperature range of 160–230 °C. The dynamics of the crystal lattice in the composites were studied using optical and FTIR spectroscopy. The magnetization curves M(H) of the composites are characterized by weak ferromagnetism, which is due to the substitution of (Ti/Zr)4+ by Fe3+ in the crystal lattice. This substitution leads to structural distortions and the appearance of ferromagnetic ordering in the composite materials. [ABSTRACT FROM AUTHOR]

The present study investigates the concentration dependence of physical properties and structural parameters of YbMn1−хFeхO3 (YbMF) compositions, which were nanostructured using the mechanical activation method at a pressure of 1 GPa. Using X-ray diffraction, the dependence of the unit cell parameters of the H-hexagonal (P63cm) and O-orthorhombic (Pnma) phases on the Fe3+ dopant concentration was studied. It was found for the first time that a morphotropic region (MR) was formed in YbMF in the concentration range x = 0.6–0.8, characterized by the coexistence of H and O-phases. At the point х = 0.5, the minimum values of all bond lengths of the H-phase were observed, while at х = 0.8, the bond length minimum of the YbO8 dodecahedra of the O-phase was observed. The tilt θ° and rotation φ° angles of oxygen octahedra MnO6/FeO6 of the O-phase also vary with the Fe3+ concentration in the range of (19.354–19.754)° and (12.648–12.677)°, respectively. Using the complex impedance method Z* = Z′(ω) − j·Z″ (ω), the study showed that the relaxation character was non-Debye. Theoretical and experimental curves were obtained for each YbMF composition at different temperatures, along with the corresponding equivalent circuits. The study also investigated the parameters of the stochastic magnetic domain structure using the random magnetic anisotropy model. It was found that in the region of solid solutions of YbMF, the values of Hc and Mr have maxima at x = 0.5, and the highest value of Hc, equal to 452 Oe, is inside the MR. [ABSTRACT FROM AUTHOR]

In this work, the structural phase state and physical properties of YbMn1-xFexO3 (hereinafter YbMF) ceramics in the range of x = 0.0–1.0 with a concentration step Δx = 0.1 were studied by complex methods. X-ray diffraction revealed that the YbMF compositions in the range of x = 0.1–0.5 were hexagonal (H) phase solid solutions. In the concentration range of x = 0.6–0.8, the hexagonal and orthorhombic (O) systems coexist, and the unit cell parameters of these phases rise with increasing x. The study of the lattice parameters, bond lengths, bond angles and the main parameters of the magnetic hysteresis loop of the H-phase revealed the presence of a singular point x = 0.5 in the concentration range, where extrema of the corresponding parameters were observed. By analyzing the Cole–Cole plots for the electric modulus M*(ω), a conclusion was drawn about the thermally activated nature of the dielectric relaxation for each composition with a single relaxation time τ. The magnetodielectric MD(ω) and magnetoresistive MR(ω) coefficients measured in crossed and parallel fields E and H show high values, which reach 1.6% and 50%, respectively, depending on the frequency of the measuring field. [ABSTRACT FROM AUTHOR]

For the first time, the influence of Cerium (Ce3+) on the structural, microstructural, Fourier infrared spectroscopy, and LPG sensing behaviour of CoCr2-xCexO4 (CoCrCe) is described in this study. The solution combustion technique was used to create the CoCrCe samples. All samples were sintered for 3 h at 600 °C to achieve a pure crystalline nature free of impurities. The production of cubic spinel structures with typical crystallite sizes smaller than 16 nm is confirmed by X-ray diffraction. Because compressive lattice strain is created when Ce3+ ions are replaced by Cr3+ ions, we discovered reducing the lattice parameter. Further samples were analysed using the FTIR technique to learn about the octahedral and tetrahedral stretching bands, which confirmed the ferrite structure was free of impurities. Scanning Electron microscopy was used to examine the samples' microstructures. All of the samples were determined to be very porous. Elemental analysis was performed using energy dissipative spectra, which confirmed the presence of all elements in the samples. 2-mol% Ce3+ has the best gas sensing characteristics of any Ce concentration. Furthermore, the thin film based on CoCr1.98Ce0.02O4 may be employed as a chemiresistive gas sensor to detect LPG (10–1000 ppb) at room temperature. On LPG exposure, the constructed gas sensor demonstrates greater gas sensitivity in the order of 98% at 500 ppb, with higher stability, rapid response, and recovery time in the order of 60 s and 75 s, respectively. This study reports for the first time on the creation of an LPG gas sensor device that operates at room temperature and has high sensitivity. Because of their high gas sensitivity, rapid reaction and recovery times, and long-term stability, these material gas sensors might be ideal materials for the manufacture of gas sensors devices for the detection of LPG low concentration (ppb level). [ABSTRACT FROM AUTHOR]

This work is the first to study the influence of crystallite sizes and structural defects on the crystal structure and physical properties of bismuth ferrite BiFeO3 (BFO). Rotatable Bridgman anvils were used to generate the structural defects, with the uniaxial pressures ranging from 0.5 to 1 GPa. According to the X-ray diffraction analysis (XRD), the symmetry space group R3c remains unchanged over the entire pressure range. From the results of the complex impedance spectroscopy, it was found that the relaxation has a non-Debye character and the activation energy increased from 1.48 eV to 2.48 eV for the starting and mechanically activated samples at 1 GPa, respectively. The crystal lattice dynamics were studied by optical and FTIR spectroscopies, and it has been found that Eg varied in the range of 2.18–2.33 eV, whereas the force constant showed variation in the range of 2.2–2.4 N/cm, depending on the applied mechanical activation pressure. The magnetization curves M(H) have been described by the law of approach magnetization to saturation (LAS). Also, a possible critical crystallite size of 70 nm has been determined, at which Hc and Mr reach their maximum values. [ABSTRACT FROM AUTHOR]

In this work, the influence of simultaneous action of high pressure and shear deformation (mechanical activation) on the physical properties of synthesized YbFeO3 was studied using complex methods. The formation of crystalline structures of YbFeO3 powders with different concentrations of structural defects was carried out using Bridgman anvils. It was found that during mechanical activation, the tilting angles of FeO6 oxygen octahedra change within the range θ = 12.69–28.45°. Using X-ray diffraction, it was established that the linear unit cell parameters a, b and c change in a consistent manner with changing mechanical activation pressure, while the space-group symmetry D 2 h 16 –Pbnm is preserved. The sizes of the coherent scattering regions (D) decrease by more than 90% at the maximum mechanical activation pressure (1200 MPa). It was found that the mechanical activation pressures of YbFeO3 have a threshold value (800 MPa), above which the dislocation density decreases. According to the results of impedance spectroscopy, the nature of relaxation was found to be non-Debye and the activation energy increased from 0.649 eV for the starting sample to 1.395 eV for the sample mechanically activated sample at 1 GPa. The magnetization curves M(H) were described using the law of approach to magnetic saturation (LAS), and the critical crystallite size (Dcr) was determined to be 50 nm, at which the maximum Hc is observed. The behaviors of the spectroscopic splitting factor (g) and half-width (ΔH) of the electron paramagnetic resonance (EPR) spectrum are analogous to Hc and Mr, however, the maximum ΔH is observed in the range of 50–105 nm, and the g-factor reaches its maximum at particle sizes of 105 nm. [ABSTRACT FROM AUTHOR]

This work is the first to study the influence of crystallite sizes and structural defects on the crystal structure and physical properties of bismuth ferrite BiFeO3 (BFO). Rotatable Bridgman anvils were used to generate the structural defects, with the uniaxial pressures ranging from 0.5 to 1 GPa. According to the X-ray diffraction analysis (XRD), the symmetry space group R3c remains unchanged over the entire pressure range. From the results of the complex impedance spectroscopy, it was found that the relaxation has a non-Debye character and the activation energy increased from 1.48 eV to 2.48 eV for the starting and mechanically activated samples at 1 GPa, respectively. The crystal lattice dynamics were studied by optical and FTIR spectroscopies, and it has been found that Eg varied in the range of 2.18–2.33 eV, whereas the force constant showed variation in the range of 2.2–2.4 N/cm, depending on the applied mechanical activation pressure. The magnetization curves M(H) have been described by the law of approach magnetization to saturation (LAS). Also, a possible critical crystallite size of 70 nm has been determined, at which Hc and Mr reach their maximum values. [ABSTRACT FROM AUTHOR]

In this work, the influence of simultaneous action of high pressure and shear deformation (mechanical activation) on the physical properties of synthesized YbFeO3 was studied using complex methods. The formation of crystalline structures of YbFeO3 powders with different concentrations of structural defects was carried out using Bridgman anvils. It was found that during mechanical activation, the tilting angles of FeO6 oxygen octahedra change within the range θ = 12.69–28.45°. Using X-ray diffraction, it was established that the linear unit cell parameters a, b and c change in a consistent manner with changing mechanical activation pressure, while the space-group symmetry D 2 h 16 –Pbnm is preserved. The sizes of the coherent scattering regions (D) decrease by more than 90% at the maximum mechanical activation pressure (1200 MPa). It was found that the mechanical activation pressures of YbFeO3 have a threshold value (800 MPa), above which the dislocation density decreases. According to the results of impedance spectroscopy, the nature of relaxation was found to be non-Debye and the activation energy increased from 0.649 eV for the starting sample to 1.395 eV for the sample mechanically activated sample at 1 GPa. The magnetization curves M(H) were described using the law of approach to magnetic saturation (LAS), and the critical crystallite size (Dcr) was determined to be 50 nm, at which the maximum Hc is observed. The behaviors of the spectroscopic splitting factor (g) and half-width (ΔH) of the electron paramagnetic resonance (EPR) spectrum are analogous to Hc and Mr, however, the maximum ΔH is observed in the range of 50–105 nm, and the g-factor reaches its maximum at particle sizes of 105 nm. [ABSTRACT FROM AUTHOR]

This paper was the first to present the results of studying the influence of structural defects on the physical properties of pre-synthesized ytterbium iron garnet (YbIG). The concentration and type of structural defects were controlled by mechanically activating the powders using Bridgman anvils. Using scanning electron microscopy and X-ray diffraction (XRD), it was revealed that the particle morphology, the unit cell parameters, mean size of the coherent scattering regions (D ) and microstrains ( Δ d / d ) vary in a wide range. Using optical spectroscopy, XRD and FTIR to study the dynamic properties of the crystal lattice, showing that the bandgap and force constants of dodecahedral-coordinated ytterbium (Yb–O)d and octahedral-coordinated iron (Fe–O)o change non-monotonically with decreasing crystallite size. By analyzing the dependence of the magnetic hysteresis loop M (H) on the crystallite size D , it was concluded that there was a critical crystallite size ( D crit = 75 nm) of YbIG, at which the coercive force H c has a maximum value. For the first time, changes in g-factor and the half-width Δ H of the electron paramagnetic resonance (EPR) spectra of nanoscale crystallites were found to be correlated with the parameters of the magnetic hysteresis loop M (H) . [ABSTRACT FROM AUTHOR]

In this work, the structure and physical properties of (1 − x)(CoFe2O4) − x(PbTiO3) compositions, synthesized by the solid-phase method, were studied for the first time using complex methods. It was found that the solid-phase sintering of the inverse spinel CoFe2O4 (CFO) and the ferroelectric PbTiO3 (PTO) is frequently accompanied by the formation of additional phases—hexaferrite PbFe12O19 (PFO) and solid solutions, which were identified by X-ray diffraction, energy-dispersive X-ray analysis, and Raman spectroscopy. The dependencies of the unit cell parameters of the main components and additional phases on the concentration of PTO were studied at room temperature. The concentration interval (x = 0.3–0.7) with extreme values of structural parameters and non-monotonic changes of the physical properties was discovered. Complex quantities such as dielectric permittivity ɛ*(ω) and electric modulus M*(ω) were studied over a wide range of frequencies and temperatures using dielectric spectroscopy. The polarization switching kinetics of (1 − x)(CFO) − x(PTO) compositions were studied, and the saturated ferroelectric hysteresis loops P(E) with maximum spontaneous polarization Ps equal to 132 μC/cm2 were obtained for the first time. The bandgap Eg was determined by optical absorption spectroscopy at room temperature; Eg varies depending on the PTO concentration in the range 2.11–2.57 eV. The dynamic properties of the compositions were studied by Fourier transform infrared spectrometer (FTIR) and Raman spectroscopy. The Raman modes corresponding to PFO are well detected starting from compositions 0.3(CFO)–0.7(PTO). [ABSTRACT FROM AUTHOR]

This paper was the first to present the results of studying the influence of structural defects on the physical properties of pre-synthesized ytterbium iron garnet (YbIG). The concentration and type of structural defects were controlled by mechanically activating the powders using Bridgman anvils. Using scanning electron microscopy and X-ray diffraction (XRD), it was revealed that the particle morphology, the unit cell parameters, mean size of the coherent scattering regions (D ) and microstrains ( Δ d / d ) vary in a wide range. Using optical spectroscopy, XRD and FTIR to study the dynamic properties of the crystal lattice, showing that the bandgap and force constants of dodecahedral-coordinated ytterbium (Yb–O)d and octahedral-coordinated iron (Fe–O)o change non-monotonically with decreasing crystallite size. By analyzing the dependence of the magnetic hysteresis loop M (H) on the crystallite size D , it was concluded that there was a critical crystallite size ( D crit = 75 nm) of YbIG, at which the coercive force H c has a maximum value. For the first time, changes in g-factor and the half-width Δ H of the electron paramagnetic resonance (EPR) spectra of nanoscale crystallites were found to be correlated with the parameters of the magnetic hysteresis loop M (H) . [ABSTRACT FROM AUTHOR]

The ability to control the target physical properties of functional materials without changing stoichiometry and doping is one of the tasks of physical materials science. This work is the first to study the influence of structural defects generated under a force action combined with shear deformation (mechanical activation) on the crystal structure and physical properties of PbZr0.7Ti0.3O3 solid solution. Bridgman's anvils were used to generate structural defects. The symmetry of PbZr0.7Ti0.3O3 was best described by the space group R3m. It was found that PbZr0.7Ti0.3O3 is characterized by a non-monotonic change in the unit cell parameters (a and α) of the dislocation density (ρD) with an increase in the mechanical activation pressure. By measuring the sizes of coherent scattering regions (D) and microstrains (Δd/d), it was found that at a mechanical activation pressure of 120 MPa, a recrystallization process develops in mechanically activated powders, leading to the "healing" of the crystal structure. It is shown that by choosing the mechanical activation pressure, one can control the temperature Tm of the maximum of the dielectric permittivity εm within ΔTm = 11 °C, the Weiss constant CW, and the degree of change in the first-order phase transition. The microstructure of the compositions was studied using SEM, the dynamics of the crystal lattice were studied by X-ray diffraction analysis, optical absorption and FTIR-spectroscopy, where the controlled parameters were the root-mean-square static displacements U ¯ s 2 , the bandgap Eg and the force constants k . It was found that with a change in the pressure of mechanical activation, Eg changes nonmonotonically within the range of 3.21–3.37 eV. [ABSTRACT FROM AUTHOR]

The ability to control the target physical properties of functional materials without changing stoichiometry and doping is one of the tasks of physical materials science. This work is the first to study the influence of structural defects generated under a force action combined with shear deformation (mechanical activation) on the crystal structure and physical properties of PbZr0.7Ti0.3O3 solid solution. Bridgman's anvils were used to generate structural defects. The symmetry of PbZr0.7Ti0.3O3 was best described by the space group R3m. It was found that PbZr0.7Ti0.3O3 is characterized by a non-monotonic change in the unit cell parameters (a and α) of the dislocation density (ρD) with an increase in the mechanical activation pressure. By measuring the sizes of coherent scattering regions (D) and microstrains (Δd/d), it was found that at a mechanical activation pressure of 120 MPa, a recrystallization process develops in mechanically activated powders, leading to the "healing" of the crystal structure. It is shown that by choosing the mechanical activation pressure, one can control the temperature Tm of the maximum of the dielectric permittivity εm within ΔTm = 11 °C, the Weiss constant CW, and the degree of change in the first-order phase transition. The microstructure of the compositions was studied using SEM, the dynamics of the crystal lattice were studied by X-ray diffraction analysis, optical absorption and FTIR-spectroscopy, where the controlled parameters were the root-mean-square static displacements U ¯ s 2 , the bandgap Eg and the force constants k . It was found that with a change in the pressure of mechanical activation, Eg changes nonmonotonically within the range of 3.21–3.37 eV. [ABSTRACT FROM AUTHOR]