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Elasticity, internal friction, and thermal expansion were measured at temperatures up to 1500°C to characterize the micro‐cracking behavior of HfO2. Crack‐free HfO2 showed consistent, typical changes in these properties with temperature. Micro‐cracked HfO2 showed hysteresis in the elastic moduli and thermal expansion on thermal cycling. Internal friction increased with microcrack healing. Repeated thermal cycling and high‐temperature anneals markedly changed the microcrack system and a time‐ and atmosphere‐dependent aging effect in microcrack formation was noted.