Unexpected plasticity of potassium niobate during compression between room temperature and 900 degrees C

摘要

Single crystals of potassium niobate were compressed over a range of temperatures (21 degrees C to 900 degrees C) and examined using electron microscopy. The material did not behave in a brittle manner; samples sustained up to 3.7% strain. There was a trend of decreasing strength with increasing temperature, with a (superimposed) increase between 300 degrees C and 500 degrees C. Characterization revealed slip lines consistent with slip on {110} planes, domain activity and cracking. Dislocations consistent with the {110}< 1-10 > slip system were observed in all specimens, while dislocations most likely on the {100}< 100 > system were also observed in specimens compressed at 900 degrees C. Domain walls were observed in large numbers only in specimens tested between 300 degrees C and 500 degrees C. It is proposed that the shape of the strength-temperature curve results from the combination of contributions from dislocation slip systems and mobility and a strong effect of domain walls only acting in the intermediate temperature range. (C) 2016 Elsevier Ltd. All rights reserved.