Morphology control and negative thermal expansion in cubic ZrWMoO8 powders

Abstract

AbstractCubic ZrWMoO8 powders with rod‐like aggregate and thin fasciculus‐like and flower‐like rod cluster morphologies have been successfully fabricated with different amounts of (NH4)2HPO4 as surfactant using a hydrothermal method. X‐ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry were utilized to investigate the influence of the addition of (NH4)2HPO4 on the crystallization process and crystal morphology of the resulting products. The results show that the purity and the thermal expansion property of the resulting products are not influenced by the addition of (NH4)2HPO4. The cubic ZrWMoO8 powders with both rod‐like aggregate and flower‐like rod cluster morphologies show a positive thermal expansion property in the temperature range from room temperature to 120 °C, while they show a negative thermal expansion property in the temperature range from 120 °C to 700 °C. The abnormal thermal expansion property of cubic ZrWMoO8 below 120 °C is caused by the presence of water molecules. Investigations also show that the essence of the different morphologies of the ZrWMoO8 particles obtained is the result of the different aggregation modes of the nanorods, which act as nuclei, and the corresponding aggregation process is dominated by the addition of (NH4)2HPO4 and its amount. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)