Low-Temperature Rapid Sintering of Dense Cubic Phase ZrW_2−<i>x</i>Mo<i>_x</i>O₈ Ceramics by Spark Plasma Sintering and Evaluation of Its Thermal Properties

In this study, we report a low-temperature approach involving a combination of a sol–gel hydrothermal method and spark plasma sintering (SPS) for the fabrication of cubic phase ZrW2−xMoxO8 (0.00 ≤ x ≤ 2.00) bulk ceramics. The cubic-ZrW2−xMoxO8 (0.00 ≤ x ≤ 1.50) bulk ceramics were successfully synthesized within a temperature range of 623–923 K in a very short amount of time (6–7 min), which is several hundred degrees lower than the typical solid-state approach. Meanwhile, scanning electron microscopy and density measurements revealed that the cubic-ZrW2−xMoxO8 (0.00 ≤ x ≤ 1.50) bulk ceramics were densified to more than 90%. X-ray diffraction (XRD) results revealed that the cubic phase ZrW2−xMoxO8 (0.00 ≤ x ≤ 1.5) bulk ceramics, as well as the sol–gel-hydrothermally synthesized ZrW2−xMoxO7(OH)2·2H2O precursors correspond to their respective pure single phases. The bulk ceramics demonstrated negative thermal expansion characteristics, and the coefficients of negative thermal expansion were shown to be tunable in cubic-ZrW2−xMoxO8 bulk ceramics with respect to x value and sintering temperature. The cubic-ZrW2−xMoxO8 solid solution can thus have potential applications in electronic devices such as heat sinks that require regulation of thermal expansion