B. N. Parida

Structural, Dielectric, and Electrical Properties of BiFeWO6 Ceramic

A polycrystalline sample of BiFeWO6 was synthesized using a high-temperature solid-state reaction method. The formation of the single-phase compound was checked using an x-ray diffraction technique. The surface morphology recorded by scanning electron microscopy exhibited a uniform distribution of grains of different sizes on the surface of the sample. The existence of ferroelectric properties in the material was confirmed by temperature-dependent dielectric and polarization studies. The temperature and frequency dependence of the electrical properties (impedance, modulus, and conductivity) of the compound were studied using a complex-impedance spectroscopy technique. The frequency dependence of the modulus and impedance plots confirmed the presence of dielectric and conductivity relaxation processes of non-Debye type. The frequency dependence of the alternating-current (ac) conductivity obeys Jonscher’s universal power law.

Electrical properties of Na 2 Pb 2 R 2 W 2 Ti 4 V 4 O 30 (R = Dy, Pr) ceramics

The polycrystalline samples of complex tungsten bronze (TB) Na2Pb2R2W2Ti4V4O30 (R=Dy, Pr) compounds were prepared by solid-state reaction technique. Room- temperature preliminary structural studies confirm the formation of the compounds in the orthorhombic crystal system. Detailed studies of electrical properties of the materials using complex impedance spectroscopy technique exhibit that the impedance and related parameters are strongly dependent upon temperature and microstructure (bulk, grain boundary, etc). An observation of negative temperature coefficient of resistance (NTCR) suggests the materials have semiconducting properties. The variation of AC conductivity with temperature shows a typical Arrhenius behavior of the materials. Both the samples obey Jonscher’s universal power law. The existence of hopping mechanism in the electrical transport processes in the system with non-exponential type of conductivity relaxation is confirmed by electrical modulus analysis.

Ferroelectric phase transition and conduction mechanism of Li2Pb2La2W2Ti4Ta4O30

The polycrystalline sample of Li2Pb2La2W2Ti4Ta4O30 was synthesized by a high-temperature solid-state reaction route. Room temperature X-ray structural analysis and scanning electron micrograph show the formation of single phase high density compound. Existence of ferroelectricity in the in the compound was confirmed through detailed studies of its dielectric and polarization characteristics. From the impedance and modulus analysis it has been concluded that the charge carriers of the material have both short as well as long range order. Again, the electrical transport properties in the material are due to hopping of small polarons.

Structural, dielectric and electrical properties of a new tungsten bronze ferroelectric ceramics

The polycrystalline sample of Li2Pb2Nd2W2Ti4Ta4O30 was prepared by a solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of a single phase compound. The morphology of the sintered sample recorded by scanning electron microscope exhibits a uniform grain distribution. Detailed studies of the nature of variation of dielectric constant, tangent loss and polarization with temperature and frequency confirmed the existence of ferroelectricity in the material. The temperature and frequency dependence of impedance parameters (impedance, modulus, etc.) of the material exhibits a strong correlation of its micro-structure (i.e., bulk, grain boundary, etc.). The nature of variation of pyroelectric-coefficient and current with temperature suggests that material has good pyroelectric properties useful for pyroelectric detector.

Phase transition in tungsten–bronze Li2Pb2Nd2W2Ti4Nb4O30 ferroelectric

The polycrystalline sample of Li2Pb2Nd2W2Ti4Nb4O30 was prepared by a solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of a single-phase compound. The morphology of the sintered sample recorded by scanning electron microscope exhibits a uniform grain distribution. Detailed studies of the nature of variation of dielectric constant, tangent loss, and polarization with temperature and frequency confirmed the existence of ferroelectricity in the material at room temperature. The temperature and frequency dependence of impedance parameters (impedance, modulus, etc.) of the material exhibits a strong correlation of its microstructure (i.e., bulk, grain boundary, etc.). Furthermore, the temperature dependence of DC conductivity shows a typical Arrhenius behavior of the material. The nature of variation of pyroelectric coefficient and current with temperature suggests that material has good pyroelectric properties useful for pyroelectric detector.

Diffuse ferroelectric phase transition in Li2Pb2Dy2W2Ti4V4O30

Tungsten–bronze polycrystalline ceramic Li2Pb2Dy2W2Ti4V4O30 was prepared by mixed-oxide method. The preparation conditions were optimized by thermogravimetry analysis and repeated firing. Room-temperature structural analysis confirms the formation of the compound in single phase (orthorhombic). Studies of dielectric parameters () of the compound with temperature at different frequencies suggest the existence of phase transition in the compound. The existence of ferroelectric property (based on dielectric anomaly) of the material was confirmed by polarization study.

SYNTHESIS AND CHARACTERIZATION OF COMPLEX FERROELECTRIC OXIDE

The polycrystalline sample of Li2Pb2Pr2W2Ti4V4O30 was prepared by a solid-state reaction technique. The preparation conditions of the compound have been optimized using thermal analysis (DTA and TGA) technique. Room temperature structural analysis confirms the formation of single phase compound in orthorhombic crystal system. The surface morphology of the sample, recorded by scanning electron microscope, shows uniform grain distribution on the surface of the sample. The observation of hysteresis loop confirmed that the material has ferroelectric properties at room temperature. Electrical properties of the material were studied by complex impedance spectroscopic technique. Temperature dependence of electrical parameters (impedance, modulus, etc.) is strongly correlated to the micro-structural characteristics (bulk, grain boundary, etc.) of the sample. A typical temperature-dependent resistive characteristic of the sample (i.e., negative temperature coefficient of resistance (NTCR)) exhibits its semiconducting properties. The temperature dependence of dc conductivity shows a typical Arrhenius behavior. A signature of ionic conductivity in the system was observed in ac conductivity spectrum. The sample obeys Jonschers universal power law. The hopping mechanism for electrical transport properties of the system with nonexponential-type conductivity relaxation was suggested from the electrical modulus analysis.

Structural, Dielectric and Pyroelectric Properties of Praseodymium Based Complex Tungsten Bronze Ferroelectrics

This paper highlights the structural, dielectric and pyroelectric properties of two complex tungsten bonze ceramics (K2Pb2Pr2W2Ti4Nb4O30 and K2Pb2Pr2W2Ti4Ta4O30) which were prepared by high temperature mixed oxide method. Room temperature X-ray structural analysis confirms the formation of the compounds in single phase. SEM micrographs show uniform distribution of densely packed rod like grains. Variation of dielectric parameters with temperature and frequency shows the phase transition at 350°C and 426°C for the respective samples. Temperature dependent hysteresis loop confirms the existence of ferroelectricity in the materials. The current variation with voltage at different temperatures shows the semiconductor like behaviour of the materials. The temperature dependent dc conductivity follows the Arrhenius equation, and reveals the negative temperature coefficient of resistance (NTCR) behaviour of the materials. The current (for a fixed voltage) variation with temperature shows that the materials have high pyroelectric co-efficient and figure of merit, thus making them useful for pyroelectric sensors.

Dielectric and electrical properties of lanthanum modified electroceramics

ABSTRACT This article highlights the dielectric and electrical properties of the polycrystalline sample of K2Pb2La2W2Ti4Ta4O30, which was synthesized by high temperature solid state reaction method. The phase formation of the desired compound was confirmed by preliminary X-ray structural analysis. The scanning electron microscope photo shows uniform grain distribution throughout the surface of the sample without many pores. The polarization variation with field and temperature confirmed the existence of ferroelectricity in the material. The temperature dependence of impedance parameters of the material exhibits a strong correlation between its micro-structure and electrical properties. The nature of temperature dependent dc conductivity follows the Arrhenius equation. The values of pyroelectric current shows that the material can be useful for heat sensing applications with a working temperature of about 500°C.

Impedance and Modulus Analysis of Na2Pb2Pr2W2Ti4V4O30

The polycrystalline sample of tungsten bronze (TB) structured compound Na2Pb2Pr2W2Ti4V4O30, sample was prepared by a mixed‐oxide / solid state reaction technique. Preliminary structural studies with X‐ray diffraction data shows the formation of single phase compound. Electrical properties of the material have been studied using complex impedance spectroscopy technique. It appears that temperature dependent electrical parameters are strongly correlated to the microstructure (i.e., presence of bulk, grain boundary, etc) of the sample. An observation of a typical negative temperature coefficient of resistance (NTCR) of the sample shows semiconducting properties. The temperature dependent dc conductivity shows typical Arrhenius behavior. The sample obeys Jonschers universal power law. The possibility of hopping mechanism for electrical transport properties of the system with non exponential type conductivity relaxation was found from Modulus analysis.