A critical evaluation of reactive templated grain growth (RTGG)mechanisms in highly [001] textured Sr_(0.61) Ba_(0.39)Nb_2O_6 ferroelectric-thermoelectrics

摘要

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_(0.61) Ba_(0.39)Nb_2O_6 ceramics produced from reactive SrNb_2O_6 and BaNb_2O_6 matrix powders and acicular KSr_2Nb_5O_(15) (KSN) templates. Above 1100 ℃, Sr_xBa_(1-x)Nb_2O_6 (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 ℃) and accounts for~60% of the texture in dense SBN ceramics. A later TGG process occurs from 1250-1350 ℃ and is characterized by simultaneous densification, grain growth, and additional texture development.