Phase equilibria in the ZrO2–HfO2–Gd2O3 system at 1500°C and 1600°C

The present study examined the phase equilibria of a zirconium-hafnium dioxide-gadolinium oxide system. The study was conducted at temperatures of 1,600°C and 1,500°C. Based on the results, isothermal sections were constructed at these temperatures. The study revealed that solid solutions form in the ZrO 2 –HfO 2 –Gd 2 O 3 ternary system at these temperatures on a monoclinic (M, space group P2 1 /c) modification of HfO 2 , a tetragonal (T, space group P4 2 /nmc) modification of ZrO 2 , cubic C-type (space group Ia-3) and monoclinic (B, space group C2/m) modifications of Gd 2 O 3 , a cubic fluorite-type structure (F, space group Fm-3m), and a phase with an ordered pyrochlore-type structure of Gd 2 Hf 2 O 7 (Gd 2 Zr 2 O 7 ) (Py, space group Fd-3m). The phase boundaries and unit cell parameters of the formed phases were determined. No new phases were formed in the ZrO 2 –HfO 2 –Gd 2 O 3 system at these temperatures.