Hydrothermal synthesis of nanoplates assembled hierarchical h-WO3 microspheres and phase evolution in preparing cubic Zr(Y)O2-doped tungsten powders

Three-dimensional hierarchical h-WO3 and doping tungsten powders have recently attracted considerable attention because of their superior sensing properties and refined grains, respectively. In this article, we report a facile hydrothermal hydrogen reduction process for preparing hierarchical h-WO3 microspheres that self-assemble with nanoplates. Meanwhile, the phase evolution process and evolution mechanisms during the conversion of h-WO3 to W are systemically investigated. Results indicate that the highly homogeneous h-WO3 microspheres are uniformly covered with ultrafine ZrY2(OH)(10) micelles, which fully transform into m-WO3 and cubic Zr(Y)O-2 after calcination at 600 degrees C. Microspheres possessing different pore diameters and containing nanosized particles can be obtained by adjusting the hydrogen reduction process. These phase evolution process can provide reasonable guidance for preparing tungsten oxide with high electrochemical properties and ultrafine tungsten powders. The h-WO3 microspheres with an average size of 3 mu m consist of nanoplates and the tungsten powders doped with 1.0 wt% Zr(Y)O-2 have a mean particle size of approximately 1.4 mu m. Comparative test results indicate that the addition of 1.0 wt% Zr(Y)O-2 can promote the formation of low-degree particle agglomerates. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.