Evolution of the electrical properties of K0.5Bi0.5TiO3 as a result of prolonged sintering

Lead-free piezoelectrics are materials exhibiting great potential, particularly because of their extended strains under high fields. However, the reported electrical properties remain inconsistent due to difficulties related to sample preparation. Here, we describe peculiarities of the synthesis procedure and their influence on the electrical properties of K0.5Bi0.5TiO3 ceramics. This synthesis is characterized by the formation of K- and Bi-rich secondary phases and a reaction with humidity, which has a strong impact on the dielectric, ferroelectric and piezoelectric properties. These are very much improved after prolonged sintering, ascribed to the elimination of the hygroscopic K2O-rich phase. This is reflected in a higher resistivity, density and grain size. The electrical properties are improved in terms of a decrease in the dielectric losses, a two-fold increase in the permittivity value at the maximum, an increase in the remanent polarization to 29 μC/cm2, and an increase in the small signal d33 value from 40 to 120 pC/N.