Growth of Single Crystals of Rare Earth Phosphates

Abstract

Interest in single crystals of phosphates, especially rare earth phosphates (REP), has emerged practically only in the last decade due to attempts to fabricate miniature lasers [1, 2]. A method was developed for preparation of REP as single crystals from highly concentrated aqueous solutions of phosphoric acids at 300–700°C [1–6]. Yoshimura et al. [7] classify growth of REP single crystals under these conditions as a hydrothermal method, although the partial pressure of water is very low, usually less than 105 Pa. This can be considered to be a limiting case of the hydrothermal method for which a water vapor pressure of several hundreds of atmospheres is typical. However, considering the specifics of the method for preparation of single crystals of REP in phosphoric acid solutions at high temperature, it should be viewed as an independent route different from the hydrothermal one.