Elastic Softening in Zirconia During Stage III of Flash Experiments

Abstract

We report in-situ measurements of the elastic modulus of dense polycrystalline zirconia held in a constant state of flash, i.e. during Stage III of flash experiments. The modulus, measured with and without flash, is lowered by 10 - 35 %, in the temperature range of 1100-1400 oC. The specimen temperature, measured with a pyrometer, was consistent with the estimate from a black body radiation model. These measurements echo recent publications on the role of phonons in the onset of flash, namely the Debye temperature as a lower bound for flash, and the formation of Frenkel pairs in molecular dynamics calculations by the proliferation of phonons above the Debye temperature. However, several questions remain, for example, the rise in electrical conductivity, and electroluminescence that are nearly universal signatures of the flash phenomenon.