High-temperature deformation behavior in SrTiO_3 ceramics

摘要

The high-temperature deformation behavior of a polycrystalline strontium titanate (SrTiO_3) ceramic (6 mu m grain size) was investigated at temperatures of 1200-1345 deg C in an argon atmosphere. Compressive deformation tests were conducted at strain rates ranging from 5 X 10~(-6) to 5 X 10~(-5) s~(-1). Steady-state flow stresses were 0.05-30 MPa and increased with increasing strain rates. Stress exponents of approx = l, at temperatures >1200 deg C, indicated a viscous diffusion-controlled deformation with an activation energy of approx = 628 + - 24kJ/mol. Comparison of activation energy with literature data suggests diffusion of cations as the rate-controlling mechanism. Absence of cavitation and grain-shape changes were consistent with grain-boundary sliding as the principal deformation mechanism. The electron back-scattered diffraction (EBSD) technique was used to determine the grain orientation as a function of applied strain. The results indicate that some of the grains rotate with cumulative rotation as large as 7 deg at a strain of 4 percent.