Fast densification of dense nano-grained Gd2Zr2O7 ceramic prepared by two-step microwave sintering

Gadolinium zirconate (Gd2Zr2O7) is a candidate phase of ceramic waste form for immobilizing high-level nuclear waste. Dense fine-grained ceramics is beneficial to improve the irradiation resistance and leaching resistance of the ceramic waste form. In this work, two-step microwave sintering (TSMS) on Gd2Zr2O7 was firstly demonstrated as a considerable approach to fabricate dense nano-grained Gd2Zr2O7 ceramic. Microstructure evolutions and densification processes of the Gd2Zr2O7 samples at various temperatures were investigated. The nano-grained (69.2 nm) Gd2Zr2O7 ceramic with a relative density of 96.9% has been successfully fabricated at 1350 °C - 3 min - 1200 °C - 20 min. TSMS can promote the near complete densification of ceramics while suppressing the growth of crystal grains within nanoscale (<100 nm) by taking advantages of microwave sintering and two-step sintering.