Rapid microwave synthesis and structural phase diagram of Ln _xY_1-xMnO₃

YMnO₃ is one of the primary examples of a multiferroic ceramic. We present a novel solid-state microwave sintering method for making high-purity ceramic samples of YMnO₃ and related compounds in a few hours. This leads to determination of the structural phase diagram for the formation of single-phase, hexagonal samples when doping lanthanides into YMnO₃. It is found that the solidstate microwave synthesis allows manufacture of high-quality samples in hours rather than days. The resulting phase diagram accords well with results from the literature, and from calculations based on the Goldschmidt tolerance factor for the stability of perovskite structures, suggesting that the transformation from hexagonal to perovskite with doping is driven essentially by ion sizes. Some results concerning the microwave synthesis of BaLnInO₄ compounds, where Ln is a lanthanide, are noted. Microwave sintering of BaNdInO₄ yields single-phase samples where conventional sintering does not.