A series of mixed fluorides with general composition Ba1-xNdxF2+x (0.00 less than or equal to x less than or equal to 1.00) was prepared by vacuum heat treatment of the mixture of starting fluorides, and analyzed by powder XRD. From the XRD analysis, the low temperature phase equilibria in BaF2-NdF3 system is elucidated. The initial compositions in this series, that is, up to the nominal composition Ba0.65Nd0.35F2.35 (x less than or equal to 0.35) exist as cubic fluorite-type solid solution. Beyond the solid solution limit, that is, x > 0.35, a rhombohedral fluorite related ordered phase is observed. Further, NdF3-rich compositions (x greater than or equal to 0.50) exist as a mixture of rhombohedral ordered phase and NdF3 (tysonite)-type phase. About 10 mol% of BaF2 could be retained in the NdF3 lattice, forming a tysonite-type solid solution, under the short annealed and slow cooled conditions. (C) 2003 Elsevier Science Ltd. All rights reserved.