Internal Friction in ZrO₂ Containing CaO

Internal friction was measured on polycrystalline ZrO₂ containing 4, 7, 10, 13, 16, and 20 mole percent CaO. In the range 10 to 20 percent a symmetrical internal friction peak occurs with its maximum at about 300 °C at 1 kHz; below 10 percent a nonsymmetrical peak occurs at somewhat higher temperature which may be associated with the presence of two phases. The symmetrical peak in as-sintered specimens has the same dependence on CaO content as that reported for electrical resistivity at 1000 °C and is probably caused by motion of oxygen vacancies. Annealing at 1000 °C for 1000 hours causes reduction of the peak height but with a different composition dependence from that reported for annealing of electrical resistivity. The results suggest that oxygen vacancies in calcia stabilized zirconia exist in several states of binding but that detailed models are likely to be complex.