A selective filter is an important component in a high‐efficiency thermophotovoltaic (TPV) system. Compared to dielectric stack interference filters, semiconductor plasma filters have the potential for higher performance at lower cost. Conventional transparent conductive oxides (TCOs), such as ITO, SnO2, and ZnO, are inadequate for low temperature (800–1200 °C) TPV system applications, because of their low mobility (∼20 cm2 V−1 s−1) and high carrier concentration (≳5×1020cm−3). A cadmium stannate (Cd2SnO4) based selective filter has been developed in this study. We will report experimental results on Cd2SnO4deposited by r.f. magnetron sputtering. The principle variables investigated were the composition of the sputtering gas, the substrate temperature, and the conditions of post‐deposition thermal treatment. The electrical, optical, and compositional properties of the films have been characterized using Hall effect measurement, optical and infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, and atomic force microscopy. Mobilities as high as 65 cm2 V−1 s−1with a carrier concentration 2–3×1020cm−3have been obtained. The results indicate the ability to control the short‐wavelength transmittance, the long‐wavelength reflectance, and the position and abruptness of the plasma edge. The plasma edge can be controlled between 1.5 and 3.0 &mgr;m. ©1996 American Institute of Physics.