A critical evaluation of reactive templated grain growth (RTGG) mechanisms in highly [001] textured Sr_0.61Ba_0.39Nb₂O₆ ferroelectric-thermoelectrics

In reactive templated grain growth (RTGG), oriented template crystals are used to seed both phase formation and crystallographic orientation in textured ceramics. This mechanism differs substantially from templated grain growth (TGG), in which texture forms via grain growth mechanism. In this work, characteristics of both RTGG and TGG processes are evaluated in [001] textured Sr_0.61Ba_0.39Nb₂O₆ ceramics produced from reactive SrNb₂O₆ and BaNb₂O₆ matrix powders and acicular KSr₂Nb₅O₁₅ (KSN) templates. Above 1100 °C, Sr_xBa_1-xNb₂O₆ (SBN) forms by oriented nucleation and growth on KSN (the RTGG process) and by nucleation of nonoriented matrix grains. RTGG occurs without densification or coarsening until phase formation is complete (∼1250 °C) and accounts for ∼60% of the texture in dense SBN ceramics. A later TGG process occurs from 1250-1350 °C and is characterized by simultaneous densification, grain growth, and additional texture development.