The Systems Y 2 O 3 ‐ P 2 O 5 and Gd2 O 3 ‐ P 2 O 5

The systems and each contain six intermediate compounds of 4:1, 3:1, 1:1, 1:2, 1:3, and 1:5 ratios. The systems were investigated by solid‐state reactions and also by quenching methods in the glass‐forming region between the 1:2 and 1:5 compounds. The 4:1, 1:2, 1:3, and 1:5 compounds in the two systems appear to have identical or similar structures, whereas the 3:1 and 1:1 compounds differ in structure. It was found that the 4:1 and 3:1 compounds in the refractory portion of the systems have lower temperature limits of stability. The newly discovered 1:2 compounds in each system are relatively stable, decomposing to 1:1 and 1:3 near 1450°C and melting incongruently to 1:1 and liquid near 1305°C. The 1:3 compounds melt congruently and the 1:5 compounds melt incongruently to 1:3 and liquid.