Synthesis, sintering, and grain growth kinetics of Hf6Ta2O17

A systematic study of the solid-state synthesis, pressureless sintering, and grain growth kinetics of Hf6Ta2O17 is presented. The ideal conditions for solids-state synthesis of Hf6Ta2O17 powder with minimal particle necking was 1250 degrees C for 2 h in air. The resultant powder has an average particle size of 210 +/- 70 nm. The combined synthesis and ball-milling procedure produces highly sinterable Hf6Ta2O17 powder, achieving > 97 % of theoretical density after pressureless sintering at 1600 degrees C for 2 h in air. The grain growth mechanism was sensitive to processing conditions, appearing to be primarily driven by surface diffusion below 1600 degrees C and grain boundary diffusion above 1650 degrees C. The respective activation energies for grain growth were found to be QS = 659 +/- 79 kJ mol-1 and QGB = 478 +/- 63 kJ mol- 1.