The focus of this paper is to evaluate thick, 20ϫ 20ϫ 10 and 10ϫ 10ϫ 10 mm 3 , cadmium zinc telluride ͑CZT͒, Cd 0.9 Zn 0.1 Te, crystals grown using the traveling heater method ͑THM͒. The phenomenal spectral performance and small size and low concentration of Te inclusions/precipitates of these crystals indicate that the THM is suitable for the mass production of CZT radiation detectors that can be used in a variety of applications. Our result also proves that with careful material selection using IR and high-quality fabrication processes, the theoretical energy resolution limit can be achieved.