A method for forming a high purity, copper indium gallium selenide (CIGS) bulk material is disclosed. The method includes sealing precursor materials for forming the bulk material in a reaction vessel. The precursor materials include copper, at least one chalcogen selected from selenium, sulfur, and tellurium, and at least one element from group IIIA of the periodic table, which may be selected from gallium, indium, and aluminum. The sealed reaction vessel is heated to a temperature at which the precursor materials react to form the bulk material. The bulk material is cooled in the vessel to a temperature below the solidification temperature of the bulk material and opened to release the formed bulk material. A sputtering target formed by the method can have an oxygen content of 10 ppm by weight, or less.