High-temperature solid-state reactions in the (1-x)Na0.5Bi0.5TiO3-xSrTiO3 system

High-temperature reactions during the solid-state synthesis of samples from the (1-x)Na0.5Bi0.5TiO3-xSrTiO3 system were investigated. Due to the number of chemically different elements, the processing of these ceramics is delicate and requires several firing steps under specific conditions to obtain phase-pure samples. Sintering in an air atmosphere resulted in a macroscopically inhomogeneous microstructure, which is a consequence of incomplete reaction between different secondary phases. However, prolongation of the sintering time aggregated the pores in the sample, while at a higher firing temperature the sample's secondary phase melted. As a result, the nominal composition was altered, leading to the formation of the Na2Ti6O13 secondary phase. Sintering under an increased oxygen pressure of 1 MPa limited the evaporation of the secondary phase. This allowed the completion of the reaction, forming a homogeneous and dense sample. The study provides a set of experimental conditions for the successful preparation of ceramics from the investigated system.