Effect of acids on the morphology and negative thermal expansion analysis of ZrW2O8 powders prepared by the hydrothermal method

Different acids were used to prepare ZrW2O8 powders at 570 °C by the hydrothermal method. The products were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, thermogravimetric and differential scanning calorimetry and Fourier transform infrared absorption spectra. The results indicate that among the chosen acids, only HCl and HNO3 can be used to prepare pure ZrW2O8 powders with high crystallinity and rod-like shape. When the hydrothermal temperature reduces to 160 °C, nano-sphere particles with an average diameter of 30 nm is obtained, if prepared by HNO3 addition. The results of in situ X-ray diffraction measurement indicate that ZrW2O8 powders prepared by pure HCl or HNO3 have strong negative thermal expansion.