Preparation of dense negative-thermal-expansion oxide by rapid quenching of ZrW2O8 melt

Abstract

By rapid quenching of ZrW2O8 melt from 1300°C, dense specimens with few inner pores were successfully prepared. Dilatometry experiments were performed and an abrupt thermal expansion was observed in the range 120-160°C, probably due to removal of internal stress upon the first heating measurement from room temperature to 300°C. The specimen annealed at 200°C for removal of internal stress exhibited a negative average thermal expansion coefficient of - (4-5) × 10-6 K-1 from room temperature to 250°C, which was smaller than that of sintered ceramic ZrW2O8, (- (6-10) × 10-6 K-1). X-ray diffraction and secondary electron microscopy measurements revealed that the obtained specimen was a hybrid of ZrO2 and/or WO3 grains with ∼1 μm diameter and ZrW2O8 grains with 10-25 μm diameter. The smaller negative thermal expansion could be attributed to this hybridization due to decomposition of ZrW2O8 during the quenching process.