Perovskite NdTiO₃ in Sr- and Ca-doped BaO–Nd₂O₃–TiO₂ Microwave Dielectric Ceramics

Ba_6–3xNd_8+2xTi₁₈O₅₄ (BNT) is a useful dielectric resonator at microwave frequencies. Recent work has shown that the major secondary phase in this system can be indexed as Nd₄Ti₉O₂₄ (JCPDS 33–943). The present study has evealed that when half of the stoichiometric Ba⁺² is replaced with Ca⁺² or Sr⁺², a third, tilted perovskite-structured phase, NdTiO₃, is also present. It forms as coherent intragranular regions within BNT grains and always contains some of the divalent dopant species. The orientational relationship between NdTiO₃ and BNT has been established.