The impact of flash sintering on densification and plasticity of strontium titanate: High heating rates, dislocation nucleation and plastic flow

Abstract

Flash sintering involves very rapid densification of ceramic powder compacts during a thermal runaway induced by an applied voltage and current. The mechanisms of fast densification are still not well-understood. The present study investigates the impact of high heating rates during flash sintering on densification, dislocation density and plasticity of SrTiO3. After flash sintering, a high dislocation density of almost 1014 m−2 was observed by TEM. Uniaxial compression at 1150 °C revealed very high deformation rates. It is argued that for SrTiO3, dislocations are generated and migrate during flash sintering. This becomes possible by the very high heating rates, which conserve high driving forces for sintering up to high temperatures. High driving forces of several 10 MPa are preserved up to high temperatures. Thus, the sintering stress can be above the flow stress of SrTiO3 (5 MPa), and the nucleation of dislocations occurs, paving the path for plastic flow.