The effects of cold sintering parameters on the densification of Na2WO4 ceramics using Na2WO4·2H2O dry powders

Abstract Cold sintering process (CSP) combines transient liquid phase and/or external pressure to assist the densification of ceramics, the sintering mechanism of which is typically dominated by the “dissolution–precipitation” process. In this work, Na 2 WO 4 ·2H 2 O dry powders without liquid water have been used as the “liquid phase” to realize the densification of Na 2 WO 4 ceramics. The effects of sintering parameters on the CSP of Na 2 WO 4 ceramics using Na 2 WO 4 ·2H 2 O dry powders are systematically studied, including sintering temperature, external pressure, sintering process time and the amount of Na 2 WO 4 ·2H 2 O phase. It is found that the “liquid phase,” that is, Na 2 WO 4 ·2H 2 O is the key factor for controlling the CSP of Na 2 WO 4 ceramics, and Na 2 WO 4 ·2H 2 O hydrate shows an advantage of homogeneous dispersion of liquid water. The sintering temperature affects the densification mechanism involved with plastic deformation and the “dissolution–precipitation,” external pressure accelerates the densification process, and enough sintering process time ensures the completion of CSP. Finally, the optimum cold sintering parameters of Na 2 WO 4 ceramics by Na 2 WO 4 ·2H 2 O powders are obtained at 150°C and 240 MPa for 60 min with a pretreatment at 150°C for 30 min.