Monica Sindhu

Effect of Zr substitution on phase transformation and dielectric properties of Ba0.9Ca0.1TiO3 ceramics

Ba0.9Ca0.1Ti1−xZrxO3 (x = 0.05, 0.07 and 0.10; BCTZ5, BCTZ7, BCTZ10) lead free ceramics were prepared by solid state reaction. The phase transitional behaviour, composition, and temperature dependent electrical properties and composition dependent ferroelectric properties were investigated. XRD analysis at room temperature and Rietveld refinement revealed a structural transformation from tetragonal to rhombohedral with enhancement of Zr content in the BCT matrix. Study of impedance spectra of these ceramics confirmed a heterogeneous electrical microstructure where the conduction and relaxation mechanisms originated from grain boundaries and grains. The ceramics depicted non Debye type of relaxation. Dielectric properties illustrated a decrease in Curie temperature and a diffused phase transition behavior with increase in Zr content. The conducting species changed from V′o to V′′o on ferroelectric phase transition in grain interiors. Saturated hysteresis loops confirmed the ferroelectric nature of the cera...

Rietveld Refinement and DC Conductivity of Na0.5K0.5NbO3 Ceramics

Potassium Sodium Niobate, Na0.5K0.5NbO3 is a promising base material for lead free piezoceramics. The polycrystalline sample Na0.5K0.5NbO3 was synthesized using solid state reaction method. The crystal structure and phase purity was studied by XRD and analysed using Rietveld refinement method. Good agreement was observed between the observed and calculated patterns in Rietveld refinement. The refinement inferred orthorhombic crystal structure with Amm2 space group. The impedance spectroscopy of the sample was performed in frequency range 10 Hz to 7 MHz in temperature range 573K to 703K. The activation energy was obtained to be 0.67eV from the reciprocal temperature variation of dc conductivity which follows the Arrhenius law.

Structural and Dielectric Properties of Na0.5Bi0.5TiO3 Ferroelectric Ceramics

Na0.5Bi0.5TiO3 (NBT) ceramics were synthesized by conventional solid state reaction method. Structural and dielectric properties of these ceramics were investigated. Crystalline phase of sintered ceramics was investigated by X-ray diffraction (XRD). The Rietveld refinement of powder X-ray diffraction revealed that the prepared ceramics exhibit the rhombohedral space group R3c. Dielectric properties of Na0.5Bi0. analyzer.5TiO3 (NBT) ceramics were studied at different temperatures in a wide frequency range using impedance