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The ceramic compound CuFe2O4 was synthesised via conventional high-temperature solid-state reaction route. The structural study of the compound was done using X-ray diffraction technique. The preliminary structural study was performed using POWD software and a tetragonal structure was suggested. The Rietveld refinement of XRD (X-ray Diffraction) data was carried out using FullProf software and the refined lattice parameters were obtained as a = 5.80030 Å and c = 8.69400 Å with high tetragonality ratio. The crystallite size and lattice strain were calculated using Williamson–Hall (W-H) plot. The temperature and frequency dependent electrical properties of this compound are analysed using complex impedance technique. The impedance and modulus study of the compound showed the contribution of intra-grain effect to the overall electrical response. The studied ceramic possessed a non-Debye-type relaxation mechanism. The bulk resistance decreased with the increase in temperature, thus showing negative temperature coefficient of resistance behaviour. Modulus and conductivity study showed the evidence of conduction via hopping mechanism inside the material. Frequency-dependent AC conductivity followed Jonscher's universal power law. The Arrhenius equation was fitted with the temperature-dependent AC conductivity at different frequencies, and activation energies were determined to understand the charge species involved in the conduction mechanism. [ABSTRACT FROM AUTHOR]

In this study, the impact of Nd doping on the structural, microstructural, dielectric, ferroelectric, and transport properties of Pb (1 - x) Nd x (Fe 0.5 Nb 0.5) 1 - x / 4 O 3 (PNFN) solid solutions ( x = 0 , 0.02 , 0.04 , 0.08 , and 0.1 ) is reported. For all the solid solutions, room temperature Rietveld refined X-ray diffraction (XRD) analysis reveals the monoclinic crystal structure with Cm space group. From Field emission scanning electron microscope (FESEM) studies, the polyhedral-shaped grains are found to be homogeneously distributed. Variation of dielectric properties with temperature displays the decrease of phase transition temperature (TC) with increasing Nd content. The temperature-dependent AC conductivity follows the Arrhenius behavior and the activation energies are calculated for high temperature regions. The frequency dependent AC conductivity behavior obeys the Johnscher's power law. Impedance spectroscopy results show the impact of conductivity from the bulk (grain) and displays non-Debye type of behaviour. Electric modulus demonstrates thermally activated relaxation phenomenon in the materials. Polarization vs. electric field (P-E) loops analysis confirms the ferroelectric nature of the materials. With increase in Nd concentrations, the value of remanent polarization (2Pr) increases, on the other hand, the coercive field (2Ec) value decreases. Both of these properties are suitable for enhancement of the physical properties of the multiferroic materials. [ABSTRACT FROM AUTHOR]

The effect of Sm doping on structural, dielectric, multiferroic and electrical properties of GaFeO3 with composition GaFe1-xSmxO3 (x = 0, 0.05, 0.10, 0.15) is studied. Rietveld refinement of the XRD data reveals the formation of single-phase orthorhombic structure. It is observed that the unit cell volume increases with rise in Sm content. FESEM study reveals that the irregular-shaped grains are uniformly distributed throughout the surface. From dielectric plot, a significant variation in εr and tanδ with Sm content is observed. Further, conjugate existence of both ferroelectric and magnetic ordering is confirmed by polarisation and magnetization hysteresis loop measurement. The remanent polarisation (Pr) is decreased with Sm content due to the defects related to fluctuations in the valance of Fe in the studied samples. Also, the remanent magnetization (Mr) is found to fall with rise in Sm content due to the lower magnetic moment (μ) of Sm3+. Impedance analysis shows the existence of two types of relaxation in studied materials. [ABSTRACT FROM AUTHOR]

The effect of Sm doping on structural, dielectric, multiferroic and electrical properties of GaFeO3 with composition GaFe1-xSmxO3 (x = 0, 0.05, 0.10, 0.15) is studied. Rietveld refinement of the XRD data reveals the formation of single-phase orthorhombic structure. It is observed that the unit cell volume increases with rise in Sm content. FESEM study reveals that the irregular-shaped grains are uniformly distributed throughout the surface. From dielectric plot, a significant variation in εr and tanδ with Sm content is observed. Further, conjugate existence of both ferroelectric and magnetic ordering is confirmed by polarisation and magnetization hysteresis loop measurement. The remanent polarisation (Pr) is decreased with Sm content due to the defects related to fluctuations in the valance of Fe in the studied samples. Also, the remanent magnetization (Mr) is found to fall with rise in Sm content due to the lower magnetic moment (μ) of Sm3+. Impedance analysis shows the existence of two types of relaxation in studied materials. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Bi 1 − x LaxFeO3 [ x = 0. 5 , 0.6, 0.7 and 0.8] were synthesized through high temperature solid state reaction method. The structural studies of the compounds were done using X-ray diffraction technique. Dielectric constant and dielectric loss were studied for various frequencies (100 Hz–104 Hz) at different temperatures. The temperature-dependent non-Debye type relaxation process was suggested in the materials from the analysis of frequency-dependent electrical data at different temperatures. Temperature dependence of dc and ac conductivity at various frequencies showed negative temperature coefficient of resistance (NTCR) behavior. The frequency dependence of ac conductivity at different temperatures obeyed Jonscher's universal power law. The temperature dependence of dc and ac conductivity was fitted to Arrhenius equation. The activation energies at different temperature ranges were calculated to know the charge species involved in the conduction process. [ABSTRACT FROM AUTHOR]

The polycrystalline sample of KPb2V5 O15 was prepared by a mixed-oxide method relatively at low temperature (i.e., 550°C). X-ray diffraction studies of the compound showed the formation of single phase orthorhombic crystal structure at room temperature. SEM micrograph showed the homogeneous distribution of grains throughout the sample. Electric properties were analyzed using the complex impedance spectroscopy. The modulus plot showed the presence of both the grain and grain boundary effect. The bulk impedance evaluated from the Nyquist plots was observed to decrease with the rise in temperature, showing a negative temperature coefficient of resistance. The variation of AC electrical conductivity (σAC) was measured in a wide temperature (30-500°C) and frequency (102-106 Hz) range. The activation energy of the compound calculated from both the impedance and modulus spectrum was found to be the same. [ABSTRACT FROM AUTHOR]

Polycrystalline La3/2Bi3/2Fe5O12 (LBIO) compound was prepared by a high-temperature solid-state reaction technique. The complex impedance of LBIO was measured over a wide temperature (i.e., room temperature to 500°C) and frequencies (i.e., 102–106 Hz) ranges. This study takes advantage of plotting ac data simultaneously in the form of impedance and modulus spectroscopic plots and obey non-Debye type of relaxation process. The Nyquist's plot showed the presence of grain effects in the material at high temperature. The ac conductivity spectrum was found to obey Jonscher's universal power law. The dc conductivity was found to increase with rise in temperature. The activation energy of the compound was found to be 0.24 and 0.51 eV in the low and high-temperature region, respectively, for conduction process. [ABSTRACT FROM AUTHOR]

The polycrystalline sample of LiPb2V5O15 was prepared by a mixed oxide method at low temperature (i.e. 550°C). Preliminary structural analysis confirmed the formation of the compound of an orthorhombic crystal system. The impedance parameters of the material were studied using complex impedance spectroscopy (CIS) in a wide temperature (i.e. 30–450°C) and frequency (i.e. 102–106 Hz) range. From the complex impedance plots, grain/grain boundary effects and relaxation phenomenon were observed above 30°C. Study of electrical conductivity suggests that the compound exhibits the negative temperature coefficient of resistance (NTCR) behavior like a semiconductor. [ABSTRACT FROM AUTHOR]

A polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy (CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits Arrhenius type of electrical conductivity. [ABSTRACT FROM AUTHOR]

Abstract: The polycrystalline sample of NaBa2V5O15 (NBV), a member of tungsten bronze family, is prepared by a mixed oxide-technique. X-ray diffraction (XRD) analysis shows the formation of single-phase compound with an orthorhombic structure at room temperature. Microstructural study by scanning electron microscopy (SEM) suggests that the compound has small grains distributed uniformly on the surface of the sample. Studies of electrical properties of NBV using a complex impedance spectroscopy (CIS) technique show the decrease of bulk resistance with rise in temperature indicating a typical negative temperature coefficient of resistance (NTCR)-type behavior similar to that of a semiconductor. The nature of Nyquist plots reveals the presence of bulk and grain boundary effects in NBV. A possible hopping mechanism for electrical transport processes in the system is evident from the modulus analysis. Moreover, the variation in dc conductivity is found to increase with temperature. [Copyright &y& Elsevier]

• GaFeO 3 and (Ga 0.97 Nd 0.03)(Fe 1−x Mn x)O 3 (where × = 0.01–0.03)are synthesized by ceramic method. • Ferroelectric property is enhanced with the increase of Mn content. • With increase in Mn content T c value has increased from 196.6 K (for GFO) to 202.1 K (for GNFMO2). • Temperature dependent impedance analysis of the sample shows the presence of two relaxation process. GaFeO 3 and (Ga 0.97 Nd 0.03)(Fe 1-x Mn x)O 3 (where × = 0.01–0.03)are synthesized by ceramic method. X-ray diffractometer (XRD), Field Emission Scanning Electron Microscope (FESEM), electrical properties (such as dielectric, impedance, modulus, and conductivity), P-E loop (polarization) and magnetic studies are carried out to investigate the structural, microstructural, electrical and multiferroic properties of the materials. The XRD peaks of all the specimens have pure phases with an orthorhombic crystal structure bearing Pc2 1 n space group as obtained from the Rietveld refinement. Variation of dielectric constant with temperature represents that GaFeO 3 and the doped samples exhibits dielectric anomaly well above the room temperature. It is also noticed that transition temperature increases with the increment of Mn content. The complex impedance plot exhibits two semicircles, which represents the presence of bulk and grain boundary effects. The modulus spectroscopy validates the existence of a non-Debye type of relaxation. P-E loop and PUND analysis at room temperature confirms the presence of weak ferroelectricity in the materials. However, ferroelectric property is enhanced with the increase of Mn content. [ABSTRACT FROM AUTHOR]

The polycrystalline sample of KPb2V5 O15 was prepared by a mixed-oxide method relatively at low temperature (i.e., 550°C). X-ray diffraction studies of the compound showed the formation of single phase orthorhombic crystal structure at room temperature. SEM micrograph showed the homogeneous distribution of grains throughout the sample. Electric properties were analyzed using the complex impedance spectroscopy. The modulus plot showed the presence of both the grain and grain boundary effect. The bulk impedance evaluated from the Nyquist plots was observed to decrease with the rise in temperature, showing a negative temperature coefficient of resistance. The variation of AC electrical conductivity (σAC) was measured in a wide temperature (30-500°C) and frequency (102-106 Hz) range. The activation energy of the compound calculated from both the impedance and modulus spectrum was found to be the same. [ABSTRACT FROM AUTHOR]

Abstract: The polycrystalline samples of Pb1− x Sm x (Zr0.60Ti0.40)1− x /4O3 (PSZT) where x=0.00, 0.03, 0.06 and 0.09 were prepared by a high-temperature solid-state reaction technique. The preliminary structural analysis using X-ray diffraction (XRD) data collected at room temperature has confirmed the formation of single-phase compounds in tetragonal crystal system. The morphological study of each sample using scanning electron microscope (SEM) has revealed that the grains are uniformly distributed through out the surfaces of the samples. Using complex impedance spectroscopy (CIS) technique, the electrical impedance and modulus properties of the materials were studied in a wide range of temperatures at different frequencies. The impedance analysis indicates the presence of bulk resistive contributions in the materials which is found to decrease on increasing temperature. The nature of variation of resistances with temperature suggests a typical negative temperature coefficient of resistance (NTCR) type behavior of the materials. The complex modulus plots clearly exhibits the presence of grain boundaries along with the bulk contributions in the PSZT materials. The presence of non-Debye type of relaxation has been confirmed by the complex impedance analysis. The variation of dc conductivity (bulk) with temperature demonstrates that the compounds exhibit Arrhenius type of electrical conductivity. [Copyright &y& Elsevier]

Abstract: The polycrystalline sample of Li2BiV5O15 was prepared by a mixed-oxide method, relatively at low temperature (i.e., 550°C). Room temperature XRD pattern confirms the formation of the compound with an orthorhombic crystal system. Studies of dielectric properties show that the compound exhibits an anomaly at 416°C (usually called transition temperature) at 50 and 100kHz, with diffuse-type phase transition. The electrical parameters of the material were studied using complex impedance spectroscopy in a wide temperature (30–500°C) and frequency (102–106 Hz) range. The compound exhibits non-Debye of relaxation process. The activation energy of the material was found to be ∼1.08eV in the high temperature region. [Copyright &y& Elsevier]

Some yttrium modified BiFeO 3 –PbTiO 3 (BYFO-PT) compounds have been fabricated using a standard ceramic technology (solid-state route). The structural analysis from X-ray diffraction (XRD) data ensures the formation of the rhombohedral phase of the compounds. The prepared materials have major bismuth ferrite (70%) and lead titanate (30%) with few impurity phases. The materials are found to have a high dielectric constant and low tangent loss. The relaxation mechanism is identified from the peaks appearing in impedance and modulus curves. The materials show a negative temperature coefficient of resistance (NTCR) semiconductor type behavior in the temperature range of 250 °C–400 °C. In addition, grain and grain boundary effects are observed through the Nyquist plots. The activation energy (E a) of the compounds is calculated from the slope of inverse temperature versus AC conductivity at the high-temperature range. The ferroelectric nature of the compounds is confirmed by electric field dependent polarization (PE-hysteresis) loops. Image 10942 • The preferred 0.7BYFO-0.3 PT ceramics are coming under compositional morphotropic phase boundary (MPB) region. • Dielectric, electrical, ferroelectric properties are revealed. • High dielectric permittivity and less dielectric loss are achieved after Y substitution. • Nyquist plots relate the grain and grain boundary contributions. • A well defined relaxation mechanism was identified by modulus analysis. [ABSTRACT FROM AUTHOR]