The scheelite type laser crystals LiREF4 melt congruently only for RE being one of the elements Er, Tm, Yb, Lu, or possibly Y, respectively. For RE = Eu, Gd, Tb, Dy, or Ho the corresponding scheelites undergo a peritectic melting under the formation of the corresponding rare earth fluoride. The melting behavior of LiREF4 mixed crystals with two or more RE is not yet known well. If RE is a mixture of Gd and Lu, Gd rich solid solutions melt peritectically under formation of (Gd,Lu)F3 and Lu rich solid solutions melt directly without formation of other solid phases.
Cite
@article{arxiv.0902.1413,
title = {Phase Equilibria and Crystal Growth for LiREF4 Scheelite Crystals},
author = {Detlef Klimm and Ivanildo A. dos Santos and Izilda M. Ranieri and Sonia L. Baldochi},
journal= {arXiv preprint arXiv:0902.1413},
year = {2009}
}