La³⁺ Substitution for BaBi₂Nb₂O₉ Ceramics

A BaBi₂Nb₂O₉ (BBN) powder was synthesized by the double-calcination method at 800 °C, which considerably suppressed the formation of the stable intermediate Ba₅Nb₄O₁₅ phase. Sintering of the stoichiometric BBN powder at 950 °C for 4 h resulted in the production of densified BBN ceramics with a relative density of 90%. The La³⁺ substitution was conducted for Ba-deficient BBN powders with nominal compositions of x=0.03 and 0.10 in Ba_1-xBi₂Nb₂O_9-δ, which were pre-formed by the double-calcination method prior to sintering. The result of the phase identification with XRD, microstructural observation and elemental analysis with SEM and TEM, and dielectric permittivity–temperature relationship that were obtained for the La³⁺-doped BBN ceramics suggested that the La³⁺ cations could be predominantly substituted for the Ba²⁺-sites in the tetragonal BBN structure.