Growth of large-sized sapphire boules by temperature gradient technique (TGT) 1 Supported by the Nat

Abstract Sapphire boules, 120 mm in diameter, 4 kg in weight have been grown by temperature gradient technique (TGT). Impurity elements of typical crystal are detected by glow discharge spectroscopy (GDMS) and the source of which are discussed. The transmission spectra are analyzed, from which the absorption bands of F-centers and impurities are verified.