Tailoring properties and performance of (1-x)BiScO3-xPbTiO3 based piezoceramics by lanthanum substitution

Recently, a new family of piezoelectric perovskite materials based on the solid solution (1 - x)BiMeO3-xPbTiO(3) (where Me is one or a combination of cations with sum valance +3) have been developed. Specifically, the (1 - x)BiScO3-xPbTiO(3) (BSPT) system is noted for its high Curie temperature (T-C = 450degreesC) and large piezoelectric coefficient (d(33) > 460 pC/N). Lanthanum additions, as a donor dopant in the piezoelectric system Pb(Zr,Ti)O-3 and other lead based perovskite materials, are commonly utilized to both lower Curie temperature and increase piezoelectric coefficients. In the current work, the effect of lanthanum substitution in the BS-PT system is reported. The results of lanthanum additions in the BS-PT system show no large enhancement of the piezoelectric properties. However, fine grain sized materials (<1 mum), desirable for improved mechanical properties, with Curie temperature of 365degreesC and high piezoelectric coefficient (d(33) = 465 pC/N) were successfully produced. The results of this study suggest that for low lanthanum additions, <5 mol%, internal compensation mechanisms in the BS-PT system dominate piezoelectric performance. Further grain size effects in lanthanum doped BS-PT compositions provide the first experimental evidence of significant extrinsic contributions to the piezoelectric properties in this system.