The melt temperature oscillation method (MTOM) has been used to synthesize dense single-phase AgGaSe2 polycrystalline materials, which are better than those synthesized by the conventional method. AgGaSe2 crystal 22 mm in diameter and 80 mm in length was obtained by the descending ampoule with rotation method using polycrystalline materials synthesized by MTOM. The synthesis of the polycrystalline materials and growth of AgCaSe2 single crystal were carried out in the same quartz ampoule without transfer between steps. As-grown crystal was characterized by a variety of techniques. The results demonstrated that the quality of the crystal is high. There are two cleavage faces, (112) and (101), in the as-grown crystal. The (101) cleavage face has not previously been reported. To fabricate devices, a new orientation processing technique for the AgGaSe2 crystal was developed. Wafers were cut by combining the X-ray orientation device with the standard stereogram of the (112) plane on the crystal boule with two cleavage faces, (112) and (101), Following the example of frequency-doubling devices for second harmonic generation (SHG) of the pulsed output of a 10.6 mum CO2 laser, a frequency-doubling device has successfully been fabricated by the new orientation processing technique. What is more, the method is simpler, faster, and more exact than that of the conventionally used Laue orientation method.