Deformation mechanisms in titanium dioxide single crystals

Abstract

Single crystals of TiO₂ grown by a floating-zone method have been compressed in two directions, [1 0 0] and [0 0 1], at temperatures between 300 and 1300°C in an argon atmosphere. They deformed by {10¯1 〈1 01 〉 slips, except [1 0 0] specimens tested below 600° C, where twinning preceded the slip deformation. Above 800° C, an oxygen reduction occurred during compression tests and the flow stress data were not reproducible. Below 700° C the data were reproducible and the resolved yield stress increased steeply with decreasing temperature. From the temperature and strain-rate dependences, activation analyses have successfully been performed. Activation volume becomes as small as 2b ³ at high stress, and the deformation below 700° C is concluded to be governed by the Peierls mechanism. The total activation enthalpy of deformation by the Peierls mechanism is ∼0.32eV. Applying the string model for the kink-pair formation, the results are consistent if the 〈101〉 dislocation is dissociated into two 1/2〈101〉 partial dislocations. No twinning-anti-twinning asymmetry of slip was observed.