Synthesis, processing, and characterization of negative thermal expansion zirconium tungstate nanoparticles with different morphologies

Zirconium tungstate (ZrW2O8) is a unique ceramic oxide, which exhibits a large negative coefficient of thermal expansion (CTE). While the negative CTE of bulk ZrW2O8 has been extensively characterized, the negative thermal expansion behavior of ZrW2O8 nanoparticles has never been studied. In this work, ZrW2O8 nanoparticles are synthesized with different morphologies using sol–gel and hydrothermal methods. The structural features of the nanoparticles are compared through Raman spectroscopy. The negative CTE values of ZrW2O8 nanoparticles are determined from 25 °C to 600 °C using isothermal X-ray diffraction measurements and are compared with the values obtained for bulk ZrW2O8. In the α-phase, the CTE was measured to be −12.0 × 10−6 and −13.2 × 10−6 K−1 and in the β-phase, the CTE was found to be −4.3 × 10−6 and −5.1 × 10−6 K−1 for powders synthesized by sol–gel and hydrothermal routes, respectively. The α-phase CTE for nanoparticles from both methods were higher than that of bulk ZrW2O8 (−8.9 × 10−6). The role of moisture desorption on heating in contributing to the differences observed in the α-phase CTE between the nanoparticles and bulk ZrW2O8 is discussed.