EFFECT OF ADDITIVES ON MICROSTRUCTURE DEVELOPMENT AND FERROELECTRIC PROPERTIES OF SR0.3BA0.7NB2O6 CERAMICS

Sr0.3Ba0.7Nb2O delta (SBN30) ceramics with similar to 97% theoretical density were fabricated by pressureless sintering at 1400 degrees C fo r 4 h. The sintered sample with homogeneous and small-grained (similar to 2 mu m) microstructure shows a broadened permittivity (epsilon(r)) -temperature (T) curve with epsilon(max)=1600 at T-c approximate to 17 5 degrees C. The microstructure and ferroelectric properties of the SB N30 ceramics can be substantially modified by Nb2O5 or V2O5 additive ( 0.5 mol%). The Nb2O5-added sample with isotropic grains of similar to- 4 mu m has epsilon(max) =2400 at T-c approximate to 165 degrees C. Con siderable coarsening and elongation of grains occur in the V2O5-added sample which has a markedly sharpened epsilon(r)-T character with epsi lon(max)=3500 at T-c approximate to 220 degrees C and improved spontan eous polarization of 6.4 mu C/cm(2).