E. Choukri

Studies of Diffuse Phase Transition in Ferroelectric Solid Solution Pb1-xK2xNb2O6 (x = 0.1, 0.2, 0.25 and 0.3)

New compositions of Tetragonal Tungsten Bronze (TTB) ferroelectrics Pb1-xK2xNb5O15 (PKN) with x = 0.1, 0.2, 0.25 and 0.3 were synthesized using the solid state reaction method. Structural and electrical properties were examined as a function of the ratio Pb/K using X-ray diffraction, Raman spectroscopy and dielectric measurements. The dielectric permittivity and the loss tangent of each composition have been measured in a frequency range 10 Hz–1 MH and in a temperatures range 25–600°C. It was shown that the Pb substitution induces the diffuse phase transition.

Impedance spectroscopy studies on lead free Ba 1-x Mg x (Ti 0.9 Zr 0.1 )O 3 ceramics

Abstract Ba1-xMgx(Ti0.9Zr0.1)O3 (x = 0.01 and 0.02) ceramics were prepared using the conventional solid state reaction. Rietveld refinement performed on X-ray diffraction patterns indicates that the samples are tetragonal crystal structure with P4mm space group. By increasing Mg content from 1 to 2% the unit cell volume decreased. Likewise, the grains size is greatly reduced from 10 μm to 4 μm. The temperature dependence of dielectric constants at different frequencies exhibited typical relaxor ferroelectric characteristic, with sensitive dependence in frequency and temperature for ac conductivity. The obtained activation energy values were correlated to the proposed conduction mechanisms.