High Electronically Conductive Tungsten Phosphate Glass-Ceramics

High electronically conductive tungsten phosphate glass-ceramics have been prepared by the controlled crystallization of binary 60WO₃-40P₂O₅ glass in the temperature range from 700 to 935 °C and for 1 to 24 h. The substantial increase in the conductivity for four orders of magnitude is a result of the formation of electronically conductive W₂O₃(PO₄)₂ and WO₃ phases. At low crystallization temperature the dominant W₂O₃(PO₄)₂ phase is created, whereas at 935 °C for 24 h the formation of semiconducting WO₃ crystallites of an average size of 80 nm enhances the conductivity to the highest value of 1.64 × 10^-4 (Ω cm)^-1 at 30 °C. The course of the crystallization and its impact on this exceptionally high electronic transport of binary tungsten phosphate glass-ceramics has been discussed in detail. Since such highly electronically conductive WO₃-based glass-ceramics have a great potential as cathode/anode materials in solid state batteries and as electrocatalysts in fuel cells, it is of interest to provide a novel insight into the improvement of their electrical properties.