Glass-ceramics obtained via a true bulk glassy phase offer a possibility to obtain high-temperature stable nanostructured materials in a cost efficient way which is suitable for mass production. We apply the method of glass-ceramic manufacturing to a crystalline phase which is known for its good thermoelectric properties as an n-doped material. Nb-doped SrTiO3 with grain sizes of several nanometers is obtained as the main crystalline phase from transparent bulk glass after applying a well-defined time-temperature profile for ceramization. The glass-ceramics show a low thermal conductivity of around 1.6 W/mK and a Seebeck coefficient around -480 mu V/K together with electronic conductivity. Thermal cycling of these glass-ceramics without degradation of the thermoelectric properties for temperatures up to 650 A degrees C (923 K) is shown as well.