Elastic Properties of Hafnium and Zirconium Oxides Stabilized with Praseodymium or Terbium Oxide

Elastic moduli of polycrystalline HfO 2 and ZrO 2 stabilized with 33 mol% Praseodymium oxide or terbium oxide were studied as functions of porosity and temperature. Thermal expansion was measured to 1200°C for each composition. The modulus‐vs‐porosity and thermal expansion curves were typical; however, modulus‐vs‐temperature relations were abnormally steep below 400°C, a phe nomenon observed previously for stabilized HfO 2 compositions. All compositions exhibited obvious stoichiometric changes resulting from oxidation‐reduction annealing, but only the Tb 4 O 7 ‐stabilized ZrO 2 showed any significant effect of oxidation state on the modulus values; this effect was very pronounced.