Synthesis, Vaporization and Thermodynamic Properties of Superfine Nd sub(2)Hf sub(2)O sub(7) and Gd sub(2)Hf sub(2)O sub(7)

Finely dispersed powders of neodymium and gadolinium hafnates (Nd sub(2)Hf sub(2)O sub(7) and Gd sub(2)Hf sub(2)O sub(7)) with pyrochlore structure were synthesized. Variations in particle size and morphology during thermal treatment under different conditions (1273-1673 K, 2-4 h) were studied for these compounds. The vaporization behavior of Nd sub(2)Hf sub(2)O sub(7) and Gd sub(2)Hf sub(2)O sub(7) was examined in the temperature range 2100-2750 K. In addition, the thermodynamic properties of Nd sub(2)Hf sub(2)O sub(7) and Gd sub(2)Hf sub(2)O sub(7) in the above-mentioned temperature interval were determined by using high-temperature mass spectrometry. Finely dispersed powders of Nd sub(2)Hf sub(2)O sub(7) and Gd sub(2)Hf sub(2)O sub(7) were synthesized, their temperature agglomeration processes at different conditions were examined, and special features of the vaporization process in the temperature range 2100-2750 K were investigated by high-temperature mass spectrometry. Some thermodynamic properties were also determined.