STRUCTURAL AND ELECTRICAL-PROPERTIES OF MODIFIED LEAD GERMANATE FERROELECTRICS

Polycrystalline samples of modified lead germanate, Pb(4.95)A(0.05)Ge( 2.5)Ti(0.5)O(11) (A = Ca, Sr, Pa), were prepared using solid-state rea ction techniques. X-ray powder diffraction studies of the compounds su ggest the formation of single phase materials of trigonal crystal stru cture at room temperature. Detailed studies of the dielectric constant (epsilon) and loss (tan delta) of the compounds, both as a function o f frequency (2 x 10(2) - 10(6) Hz) at room temperature and temperature (from room temperature to 200 degrees C) at 10, 100 and 1000 kHz, exh ibit a ferroelectric diffuse phase transition. The transition temperat ure is found to decrease with Ba, Sr and Ca doping at the Pb site. The biasing held and temperature dependence of dc electrical conductivity were measured for all the compounds. The nature of the ferroelectric phase transition was checked by measuring the temperature dependence o f the polarization. (C) 1998 Elsevier Science Ltd. All rights reserved .