Journal of the American Ceramic Society, July 2010, Vol.93(7), pp.1978-1983
The high‐density tungsten bronze Sr2NaNb5O15 ceramics without abnormal grain growth were successfully synthesized by a two‐step solid‐state reaction method in this work. The phase evolution and reaction mechanism in SrNb2O6 and NaNbO3 solid solutions were analyzed by X‐ray diffraction and differential scanning calorimetry. The results showed that the Sr2NaNb5O15 phase could exist stably in the temperature range of 1100°–1360°C, and would be decomposed to SrNb2O6 and NaNbO3 phases at temperatures above 1360°C. It was also found that the sintering temperature could significantly affect the density, microstructure, and electric properties of Sr2NaNb5O15 ceramics. When the sintering temperature was 1340°C, the ceramic with a near‐theoretical density and a uniform and fine‐grained microstructure was obtained, exhibiting outstanding electrical properties: ɛm=2210, tan δ=0.023, Tc=280°C, Pr=11.71 μC/cm2, and Ec=16.15 kV/cm. Further increasing the temperature to 1360°C led to the existence of some molten areas and cracks on the surface of ceramics obtained, which could significantly deteriorate the electric properties. In addition, no abnormal large grains (〉50 μm) could be found in the system and the reason was also discussed in this paper.
Sintering -- Analysis ; Sintering -- Electric Properties ; Tungsten -- Analysis ; Tungsten -- Electric Properties ; Ceramics -- Analysis ; Ceramics -- Electric Properties ; Solid Solutions -- Analysis ; Solid Solutions -- Electric Properties;
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