Preparation and electrical properties of highly conductive glass-ceramic films containing tungsten bronze

Alkali tungsten bronzes are non-stoichiometric compounds having a general formula RxWO3, where R is H, Li, Na, K and Rb and x is less than unity. They show metallic condition. The present work was done in order to obtain highly conductive glass-ceramic films containing tungsten bronze and to investigate their electric conductivities. A series of glasses consisted of compositions containing 30.0-37.5 Na2O·57.5-67.5 WO3·2.5-10.0 B2O3 (in mol percent). The melts were rapidly quenched to obtain clear glasses without devitrification. Films were prepared by two methods. One was by dipping a quartz glass plate into water dissolved Na2-O-WO3-B2O3 glasses. The other was by melting the glass powders which were uniformly dispersed on a quartz glass plate in ethanol. Tungsten bronze crystals precipitated from these films when heat-treated in a H2 atmosphere. The maximum conductivity was about 103S/cm at 25°C. The charge carrier is confirmed to be electron by Seebeck coefficient measurements. The conduction mechanism is electronic conduction due to the large polaron.