Dielectric properties of layered perovskite Sr1-xAxBi2Nb2O9 ferroelectrics (A=La, Ca and x=0,0.1)

In this letter, we report an experimental study on the influences of 10 at. % Ca2+ and La3+ doping on dielectric properties and dc conductivity of SrBi2Nb2O9 ferroelectric ceramics. All the samples were made by two-step solid-state reaction sintering at temperatures up to 1150 degrees C for 0.5-1 h in air. X-ray diffraction analysis indicated that single-phase layered perovskite ferroelectrics were obtained and no appreciable secondary phase was found. The Curie point was found to increase from 418 degrees C without doping to 475 degrees C with Ca2+ doping and to 480 degrees C with La3+ doping. Dielectric constants, loss tangent, and dc conductivity of SrBi2Nb2O9 ferroelectrics doped with Ca2+ and La3+ were studied and the relationships among doping, crystal structure, and dielectric properties were discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)04320-5].