Development of new piezoelectric ceramics with bismuth perovskites

Abstract

A new solid solution, (1-x)Bi(Ni/sub 0.5/Ti/sub 0.5/)O/sub 3/x(Pb/sub a/Ba/sub b/)TiO/sub 3/ (a+b=1) (NTPB [100x-100a/100b])is studied. The dielectric, ferroelectric, piezoelectric and mechanical properties indicate a new group of piezoelectric ceramics. One of the end member of the solid solution, BINT(a=b=0, x=0) is a mixture of a bismuth layered structure consisting of Bi/sub 4/Ti/sub 3/O/sub 12/, NiO and Bi/sub 2/O/sub 3/. When x is increased, the crystal structure changes from a mixture of bismuth layered and perovskite structures to a single phase of the perovskite structure at x=0.2-0.25, being independent of the ratio of PbTiO/sub 3/ to BaTiO/sub 3/. The crystal phase with x/spl ges/0.25 of the solid solution is a perovskite structure. The electrical properties are mainly investigated for the specimens of the perovskite structure (x/spl ges/0.25) with 0.02 wt% added MnCO/sub 3/. The electromechanical coupling factors k/sub 33/, k/sub t/ and k/sub p/ of NTPB[40-100/0]+Mn (0.02 wt%) are 0.51, 0.47 and 0.32, respectively. The mechanical bending strength of NTPB[44.5-100/0]+Mn (0.02 wt%) is about 150 MPa.