Tungsten Oxide

Tungsten oxide is the oxide state of tungsten and an important intermediate to produce tungsten from concentrate or scheelite. In 1841, chemist called Robert invested the first procedure of preparing sodium tungstate and tungsten trioxide. He is then regarded as the originator of tungsten chemistry.

Tungsten has four stable oxide states as following:

Chinese Name

English Name

Abbreviation

Chemical Formula

二氧化钨

Tungsten Dioxide

/

WO2

三氧化钨

Tungsten Trioxide;
Yellow Tungsten Oxide

YTO

WO3

蓝色氧化钨

Blue Tungsten Oxide

BTO

WO2.9

紫色氧化钨

Violet tungsten Oxide

VTO

WO2.72

Tungsten Dioxide
Tungsten dioxide is the brown crystalline monoclinic powder, it is used to prepare tungsten powder and tungsten trioxide. It can be produced by mixture of tungsten powder and WO3 by mole rate 1:2 and then heating under vacuum circumstance to 950℃. Or it can be heated by H2 airflow to reducing WO3 under 900℃.

Tungsten Trioxide
Structure of tungsten trioxide depends on temperature: it is tetragonal system when temperature reaches 740℃, orthormhombic system under 330~740℃, monoclinic system under 17~330℃, triclinic system under -50~17℃. Among which monoclinic system is the most common structure.

Blue Tungsten Oxide (BTO)
BTO is a kind of deep blue chemical compounds. It is usually formed in solution and the raw material for preparing tungsten powder. Reducing BTO to prepare tungsten powder is easier to control grain size and doping other element in tungsten powder during reduction process. As a result, BTO is gradually becoming the main raw material to prepare special tungsten powder and other products. There are three main methods to prepare BTO: calcination APT, slight hydrogen reduction of APT and inherent reduction method.

Violet Tungsten Oxide (VTO)
VTO is purple or purple blue, it can be obtained by calcinating APT under a certain temperature and reduction. VTO is mainly used to product tungsten metal powder and tungsten carbide powder, especially the fine and nano grade. Its needle shape or rod shape results in the loose appearance of cluster of grains.