Hydrothermal synthesis of ZrW2O8 nanorods

Negative thermal expansion ZrW2O8 nanorods were synthesized by a rapid low-temperature hydrothermal route, followed with a heat treatment at 500 °C for 6 h. Acidity of the HCl addition to the mixed solution in the hydrothermal condition strongly affects the formation of the precursor ZrW2O7(OH)2(H2O)2. High acidity of HCl in the range of 5–10 N facilitates the nucleation of ZrW2O7(OH)2(H2O)2, but constrains its growth. Low acidity of HCl addition (<5 N) only obtained the products ZrO2 and WO3 by firing the precursors. FE-SEM images revealed that the shape and size of ZrW2O8 were modeled after its precursor ZrW2O7(OH)2(H2O)2.