Large Seebeck Coefficients of Protonated Titanate Nanotubes for High-Temperature Thermoelectric Conversion

Titanate nanotubes Na(2-x)H(x)Ti(3)O(7) produced by alkali hydrothermally treated ground. TiO(2) aerogels are investigated as possible materials for high-temperature thermoelectric conversion by measuring their thermoelectric properties. Strikingly the Seebeck coefficients increased sharply in the temperature range 745 to 1032 K reaching a maximum of 302 mu V/K. The electrical resistivity of the TNNTs ranged from 325 to 525 Omega m, which is lower than that of bulk TiO(2), and thermal conductivities at room temperature were also very low ranging from 0.55 to 0.75 Wm(-1) K(-1). The hollow structure of the titanate nanotubes with small, uniform diameters is thought to be responsible for the ultralow thermal conductivity. The large thermoelectric power and ultralow thermal conductivity suggest that titanate nanotubes represent a new kind of p-type oxide thermoelectric material.