Holding Temperature Affects Tungsten Oxide Ceramics

It can be clearly seen from the figure that as the soaking temperature increases, the grain size of the tungsten oxide ceramic increases. When the holding temperature is 900-1000°C, there are many small-sized grains in the sample. When the holding temperature is 1050-1150 ℃, the small grains in the tungsten oxide ceramics disappear, and the grains increase obviously. Also found at 1150 ℃ insulation tungsten oxide ceramics, although the larger grain size. However, its porosity is also significantly increased, the densification of tungsten oxide ceramics worsened.

The effect of holding temperature on the grain size and relative density of the sample is shown in the figure. From the figure we can see that the grain size of tungsten oxide ceramics kept at 900-1050 ℃ for two hours slightly increased, but the relative density did not change obviously. This shows that at the above temperature, the grain growth of the tungsten oxide ceramics starts but the densification has not started or the rate of densification is small.

Tungsten oxide ceramic samples incubated at 1100 ° C for two hours have the best relative density and the grain size is relatively large. Grain growth and densification originate from the grain boundary. Each of the mass transfer phenomena and reaction processes occurring in the solid material are related to various defects in the tungsten oxide crystal lattice, and the mass transfer coefficient or reaction rate constant is directly related to the type and concentration of atomic defects. In general, the more atomic defects in the solid phase, the greater their mass transfer abilities. Tungsten oxide is an oxygen vacancy as the main defect of N-type semiconductor, at some certain temperature oxygen ions leave the grid to form oxygen vacancies.

• < Prev
• Next >