Possibility of new mixed bismuth layer-structured ferroelectrics

Possibilities of new ferroelectrics, Bi5Nb3O15 (BIN) and Bi5Ta3O15 (BTA), where A=Bi5+, B=Nb5+ and Ta5+ and k=1, in the general formula of mixed bismuth layer-structured oxides (MBLSO), Bi(4)A(2k-1)B(2k+1)O(6k+9) (k=1, 2, 3, 4), are discussed using ordinary fired, hot-pressed and hot-forged ceramics. The lattice constants are a=5.46(4), b=5.34(0) and c=21.0(1) Angstrom for BIN and a=5.43(4), b=5.39(4) and c=20.8(2) Angstrom for BTA. The D-E hysteresis loop of hot-pressed BIN at 150 degrees C indicates that BIN may be a new ferroelectric. The dielectric constant, epsilon(s), of BTA shows a peak at about 550 degrees C in the temperature-dependence curve of epsilon(s).