Lanthanum and gallium co-modified BiFeO3-PbTiO3 crystalline solutions: lead reduced morphotropic phase boundary (MPB) piezoelectric ceramics

Crystalline solutions of (1-x)(Bi,La) (Ga,Fe)O₃-xPbTiO₃ (BLGF-PT) have been developed using conventional mixed oxide ceramic processing. An attractive feature is that BLGF-PT has electrical resistivity up to 10¹³ Ω·cm at room temperatures. The MPB of (1-x)BLGF-xPT was shifted to higher x content with increasing La concentration. The La substituent was also found to decrease the ferroelectric coercive field, resulting in significantly dielectric and piezoelectric properties. The dielectric constant K and piezoelectric d₃₃ constant of 1760 and 295 pC/N have been achieved for BLGF-PT with La-20 at% and x=0.43, a composition in the vicinity of MPB. BGF-0.3PT (La-0, x=0.3) exhibited great remnant polarization Pr and strain of 67 μC/cm² and 0.4% respectively, under an electric field of 150 kV/cm. Our results clearly demonstrate that BLGF-PT is competitive and alternative piezoelectric materials to conventional Pb(Zr,Ti)O₃ (PZT) ceramics, served as piezoelectric and high power components, but in significantly lead reduced forms.