Thermal Expansion of Delta and Epsilon Zirconium Hydrides

The thermal expansion characteristics of polycrystalline delta (face-centered-cubic) zirconium hydride and epsilon (body-centered-tetragonal) zirconium hydride were determined between room temperature and 362°C and 300°C, respectively, by means of x-ray diffraction techniques. The average linear thermal expansion coefficient for the delta phase is 2.98×10—6/°C for the range 24° to 362°C. For the epsilon phase, the average coefficients for the range 24° to 300°C are —1.4×10—6/°C and 30.6×10—6/°C for the a and c directions, respectively, and 9.3×10—6/°C for the randomly oriented polycrystalline material.