Microstructure and properties of aluminium tungsten oxide ceramics synthesized by a high power cw CO₂ laser

Laser powder sintering has been used as a new technique to synthesize electronic ceramics consisting of the Al₂O₃-WO₃ system. Examination of the products by scanning electron microscopy and energy dispersive X-ray spectroscopy showed that cell structure and lateral intergrowth crystals formed in the specimens. The depth distribution of the elemental composition of the sample changed in an amplitude modulated manner. A comparison of the properties of the samples synthesized by laser and/or conventional sintering methods showed that the laser technique can produce new substances with some unique properties, such as a linear decrease in the resistivity of Al₂O₃-50 mol% WO₃ specimens with increasing temperature over the range 10 °-150 °C. X-ray photographic powder analysis indicated that the conducting phase in the specimen is non-equilibrium product: Al_xWO₃ tungsten bronze. The experiments also showed that the conductivity of samples was related to their composition and microstructure.