Thermoelectric properties of tungsten‐titanium‐phosphate glass‐ceramics.

The thermoelectric properties of tungsten‐titanium phosphate glass‐ceramics, which were described in previous articles, were measured as a function of composition, ceram temperature, and measurement temperature. The glass‐ceramics comprise tungsten monophosphate crystals, (PO2)4(WO3)2 m, in a matrix of TiP2O7. The glass‐ceramics behave as n‐type semiconductors with nearly metallic behavior. Conduction occurs along percolating networks of primarily m6 and m7 crystals. The highest electrical conductivities and (absolute) Seebeck coefficients were measured on a glass‐ceramic containing large, interconnecting, prismatic, m7 crystals. At 777°C, the electrical conductivity reached nearly 5500 S/m and the Seebeck coefficient was −60 µV/K. Thermal conductivity was in the 2.5‐3 W/m.K range, and the maximum ZT obtained was 0.007. This ZT is two orders of magnitude lower than those of the best bulk, polycrystalline, n‐type, oxide thermoelectric materials. The exceptional property of the tungsten‐titanium phosphate glass‐ceramics is their high electrical conductivity when compared with oxide glasses. [ABSTRACT FROM AUTHOR]