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In present work, Bismuth vanadate (BiVO4: BVO) ceramics is synthesized by the traditional solid-state reaction method sintered at temperature of 800℃. The phase composition and crystal structure are confirmed by the X-ray diffraction (XRD) study. The microstructural analysis is performed by the field emission scanning electron microscopy (FE-SEM). It shows that, grains are highly dense with least porosity and clear grain boundaries. For the investigation of the dielectric properties, a wide range of frequency of 100 Hz – 1 MHz and 120℃ - 200℃ temperatures domain are selected. At lower frequency, real dielectric constant (𝜀′) of BVO ceramics increases with increase in temperature. The maximum value of 𝜀′ for BVO ceramic is 427 at 120℃. Also, the tangent loss (tan 𝛿) increases with increase in temperature. [ABSTRACT FROM AUTHOR]

The zirconium (Zr) doped sodium niobate (NaNb0.75Zr0.25O3) ceramic is synthesized via traditional solid state reaction method at sintering temperature 1150°C for 4 h. The XRD analysis of NaNb0.75Zr0.25O3 (NZr) ceramic confirms single phase formation with an orthorhombic structure. The FE-SEM micrograph of NZr sample exhibit bigger grains with irregular smaller grains. The obtained value of average grain size is 1.7 µm. The analysis of dielectric properties of NZr sample is done over a wide frequency range from 100 Hz to 1 MHz in a temperature range 300°C to 360°C. The detailed study of dielectric constant and impedance spectrum suggests the low frequency dispersion (LFD) and negative temperature coefficient of resistance (NTCR) behavior of the material respectively. The conductivity analysis of sample reveals their strong dependence on applied frequency and temperature, because of the presence of singly ionized oxygen vacancies in the material. [ABSTRACT FROM AUTHOR]

BaTi0.90Sn0.10O3 (BTS) is prepared to study their structural, dielectric and impedance properties. X-ray diffraction (XRD) measurement is used for structural analysis. It is found that material has a single phase with P4mm space group. Surface morphology is studied by field emission-scanning electron microscopy (FE-SEM) and it suggests that, the BTS has small-sized grains spread uniformly in the sample. At low frequency, relative permittivity is found to be maximum. The magnitude of impedance decreases with increase of temperature, which reveals that BTS has negative temperature coefficient of resistance (NTCR) property. Moreover, the conduction mechanism of BTS is temperature-dependent at low frequency while at high frequency it is temperature independent. [ABSTRACT FROM AUTHOR]

The lead free tantalum modified NaNb1-xTaxO3 (NNT) ceramics with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 are synthesized by using conventional mixed oxide route at sintering temperature 1150 °C for 4 h. The structural analysis of NNT samples have been carried out by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM). The XRD images of NNT ceramics confirm the complete incorporation of Tantalum in NaNbO3 (NN) ceramic. With increasing the concentration of Ta, significant changes in shape of microstructure and grain growth is clearly observed in micrographs of NNT samples. The detailed study of complex permittivity (real and imaginary) of NNT samples are investigated from temperature range 313- 373K in a wide frequency range 100 Hz-5 MHz. The maximum value of real part of complex permittivity (εr) is obtained at 333 K for x = 0.3 composition of NaNb1-xTaxO3 ceramics. At higher frequency region the imaginary part of complex permittivity (εi) spectra show frequency independent behavior of the material at all measured temperatures. The low frequency dispersion (LFD) effect of the material is diminished with increasing temperature for all selected compositions of NNT samples. [ABSTRACT FROM AUTHOR]

Lead free strontium titanate (SrTiO3) ceramic was prepared via conventional solid state reaction technique sintered at 1300 °C for 2 h. The samples were characterized by XRD and FESEM for structural and morphological analysis. X-ray diffraction analysis confirmed the cubic structure of the compound with lattice parameter, a = 3.902 Å. The dielectric and conductivity properties of the prepared samples were investigated by impedance spectroscopy over a frequency range from 100 Hz to 5 MHz and between the temperature ranges from 543 K to 643 K. The dielectric constant and loss (tanδ) increases with increasing temperature at lower frequency. The complex impedance spectroscopy shows that the grain and grain boundary effect are responsible for the conduction mechanism of SrTiO3 ceramic. The results show that the dielectric properties and electrical characteristics (impedance and conductivity) of the material are strongly dependent on the temperature and frequency of the applied electric field. [ABSTRACT FROM AUTHOR]