The phase-separation induced nucleation and growth of Cs3LaCI6 nanocrystals has been studied in the GeS2-Ga2S3-La2S3-LaCl3-CsCl system for the first time. Remarkably, the precipitated chloride nanocrystals are spherical and distributed homogeneously in the glass matrix. Benefiting from the uniform structure, high transparency of the glass ceramic is maintained after heat treatment by reducing adverse optical scattering. As revealed by the absorption spectra and Judd-Ofelt calculations, the doped active rare earth ions are partially partitioned into the low-phonon-energy Cs3LaCI6 nanocrystals, resulting in the decrease of the non-radiative transition probabilities and therefore intensified photoluminescence emission of Nd3+ and up-conversion one of Er3+. (C) 2013 Elsevier Ltd. All rights reserved.