An improved thermoelectric converter device capable of effective and efficient high temperature operation is provided. The device includes at least a pair of spaced electrodes including substrates made from polished single crystal sapphire and active low and high temperature heat transfer regions contiguous with the electrodes and formed from materials selected to enhance heat transfer, particularly at high temperatures. The device is capable of more efficient operation and increased operating efficiencies over a wider range of temperatures than has heretofore been possible.