By observing the particle size and apparent density of blue tungsten oxide through SEM micrograph, when the temperature is between 400-500 degree celsius, the uniformity is the best, the FSSS size is 11.9-12.0um, apparent density is 2.49-2.50g/cm2. When the calcinating temperature is 450 degree celsius, the FSSS size is 11.9um, apparent density is 2.50g/cm2. When calcinating temperature is 500 degree celsius, FSSS size is 12.0um, apparent density is 2.49g/cm2. From the above data, when calcinating temperature is between 400-500 degree celsius, the grain is well distrubuted. Between every temperature range, grain distribution flows within a certain range, the particle size is between 10-40um. Also the apparent density is stable. Under different temperature, the average diameter of blue tungsten oxide is different.

Reduction machanism of Blue tungsten oxide

Under observation of SEM, we can verify the main phase component of blue tungsten oxide is B-tungsten oxide. The surface of blue tungsten oxide is rough with many cracks. Thanks to the cracks, during the reduction process, hydrogen can enter the inside of particle and abstraction of water. With the reduction of blue tungsten oxide in hydrogen, the oxygen atom reduces, tungsten oxide turns into Y-tungsten oxide gradually, its shape is like sheet or bar, the arrangement is irregualar.