Tungsten Oxide Ceramic XRD Pattern

The figure is a diagram of tungsten oxide ceramics sintered at different holding temperatures. Since the crystal structure of tungsten oxide ceramics is very complicated, we narrow down the scanning angle to 20-30 ° to observe the change of the triple peak of tungsten oxide ceramics. From the figure, we can see that the crystal structure of the tungsten oxide ceramic does not change substantially when it is sintered at a temperature of 900-1000°C. However, the XRD peak of the tungsten oxide ceramic moves to a small angle when sintering at a temperature of 1050-1100°C, and the blue shift occurs.

We can see that the spacing of the tungsten oxide ceramic lattice becomes larger. Tungsten oxide ceramic lattice contains a certain amount of oxygen vacancies, tungsten oxide ceramic lattice structure will appear loose her, resulting in the distance between the atoms become larger and tilt angle changes. Many oxygen vacancies appear in the crystal lattice at 1050-1100°C, which promotes its material transport. And then promote the growth of grains, but also lead to the distance between the atoms become larger and tilt angle changes. Making the tungsten oxide ceramic XRD peak shift to a small angle.

When the temperature reaches 1150 ℃, tungsten oxide evaporation began to intensify. Oxygen vacancies are generated at the same time, tungsten atoms are also reduced, making oxygen vacancies on the tungsten oxide ceramic microstructure reduced.

Early studies of the crystal structure show that the triclinic and monoclinic phases of tungsten oxide ceramics project the same in the X and Z axes. The only difference is that the tilt angle of the W-O key in the Y-axis direction is different. Oxygen vacancies generated during the sintering of tungsten oxide ceramics result in a change in the tilt angle of the W-O bond, possibly resulting in the formation of a new phase. Although the proportion of new phases on one grain may be relatively small, when many grains are combined, the composition of the new phase should be detectable. This may be the reason why tungsten oxide ceramics are two-phase and three-phase coexistence at room temperature.

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