Structural and electrical properties of La 3+ -doped Na 0.5 Bi 4.5 Ti 4 O 15 -Bi 4 Ti 3 O 12 inter-growth high temperature piezoceramics

Abstract New lead-free inter-growth piezoelectric ceramics, Na 0.5 Bi 8.5- x La x Ti 7 O 27 (NBT-BIT- x La, 0.00≤ x ≤1.00), were prepared by the conventional solid-state method. Structural and electrical properties of NBT-BIT- x La were studied. All the NBT-BIT- x La samples exhibited a single inter-growth structured phase. XRD and Raman spectroscopy revealed a reduced orthorhombicity, which strongly supports the variation of dielectric and ferroelectric properties. Plate-like grains were found to decrease with the increasing x contents. Impedance spectra analysis indicated that oxygen vacancy defects dominated the contributions to the electrical conductivity. The increased activation energies for dc conductivity evidenced the reduction of oxygen vacancy concentration after La substitution, inducing the enhancement in piezoelectric constant ( d 33 ) and remanent polarization (2 P r ). The studies of thermal depoling indicated that the optimal d 33 of NBT-BIT-0.50La ceramics still remained 22 pC/N at 500 °C, implying that this ceramics could be potentially applied into high temperature devices.