POSSIBILITY OF NEW MIXED BISMUTH LAYER-STRUCTURED FERROELECTRICS

Possibilities of new ferroelectrics, Bi5Nb3O15 (BIN) and Bi5Ta3O15 (BT A), where A=Bi5+, B=Nb5+ and Ta5+ and k=1, in the general formula of m ixed bismuth layer-structured oxides (MBLSO), Bi(4)A(2k-1)B(2k+1)O(6k9) (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) a nd c=21.0(1) Angstrom for BIN and a=5.43(4), b=5.39(4) and c=20.8(2) A ngstrom for BTA. The D-E hysteresis loop of hot-pressed BIN at 150 deg rees C indicates that BIN may be a new ferroelectric. The dielectric c onstant, epsilon(s), of BTA shows a peak at about 550 degrees C in the temperature-dependence curve of epsilon(s).