Effects of La substituent on ferroelectric rhombohedral/tetragonal morphotropic phase boundary in (1-x)(Bi,La)(Ga0.05Fe0.95)O3-xPbTiO3 piezoelectric ceramics

Crystalline solutions of (1-x)(Bi,La)(Fe0.95Ga0.05)O-3-xPbTiO(3) (BLGF-PT) have been fabricated with La concentrations of 0, 10, and 20 at. %. The BLGF-PT system has been found to have excellent insulation resistivity less than or equal to10(13) Omega cm. In addition, La substituent was found to decrease the coercive field, resulting in much improved dielectric and piezoelectric properties. A shift in the morphotropic phase boundary of BLGF-PT with increasing La content was identified for x=0.3, 0.4, and 0.43. We have achieved optimized dielectric constant, loss factor, Curie temperature, remnant polarization, and piezoelectric d(33) properties of 881, 0.037, 386 degreesC, 30 muC/cm(2) and 163 pC/N, respectively, for 0.6BLGF-0.4PT with 10 at. % La. These results clearly demonstrate that BLGF-PT is a competitive alternative piezoelectric material to Pb(Zr,Ti)O-3 with reduced lead content. (C) 2003 American Institute of Physics.