ZrW2O8 with Negative Thermal Expansion Fabricated at Ultralow Temperature: An Energy-Efficient Strategy for Metastable Material Fabrication

The scientific issues of the instable decomposition and manufacturing size limitation of zirconium tungstate ceramic (ZrW2O8) fabricated by the conventional high-temperature sintering process (usually T >= 1105 degrees C) are desiderated to be solved. Here, an energy-efficient cold sintering process (CSP, 190 degrees C, 1-240 min, and 350 MPa) was employed to achieve the dense fabrication of ZrW2O8 (similar to 94.3% relative density and with up to 95.9% relative density after annealing treatment) with negative thermal expansion (NTE). Utilizing the CSP, the Vickers hardness is increased to 2.62 GPa; the phase composition is determined as the ZrW2O8 phase without any decomposition. The as-fabricated ZrW2O8 ceramic reveals an excellent NTE performance over the temperature range of 0-500 degrees C. In order to demonstrate the feasibility of the low energy consumption CSP in the fabrication of the ZrW2O8 ceramic, the evolution of densification, phase composition, and microstructure are systematically analyzed, and the fundamental densification mechanism of the CSP approach is elucidated by the theory of powder sintering. This research not only effectively solves the decomposition and resultant size limitation difficulties but also establishes an energy-efficient pathway and sustainable prospects for the fabrication of more metastable-material systems.