Diffuse phase transition in modified Pb5Ge3O11 ceramics

Polycrystalline samples of Pb(4.9)A(0.1)Ge(2.5)Ti(0.5)O(11) (A = Ca, Sr, Pa ) have been prepared by solid-state reaction technique. Studies of X-ray po wder diffraction patterns of these compounds at room temperature suggest th at the compounds have been formed almost in single phase with trigonal crys tal system. Detailed studies of dielectric properties of the compounds as a function of frequency (0.2 kHz to 1 MHz) at room temperature (RT), and for temperatures RT to 200 degrees C at 10, 100 and 1000 kHz show broadening ( diffuseness) of the dielectric peaks and change of transition temperature w ith the ionic size of the dopants. Analysis of diffuseness of the dielectri c peaks shows that the values of gamma (diffusivity) lie between 1 and 2, w hich indicate the variation of the degree of disordering of the system caus ed due to substitution of different ions. Temperature dependence of electri cal conductivity and polarization of these compounds provide some interesti ng results for device fabrication.