Sol-gel processing of β-BaB 2 O 4 thin films through metal organics

(beta) -BaB 2 O 4 ((beta) -BBO) thin films were successfully synthesized by the sol-gel method using metal alkoxides. A homogeneous and stable solution was prepared by the reaction of barium metal with boron triethoxide or 2,4,6-triethoxycyclotriboroxane in a mixture of ethanol and 2-ethoxyethanol. As-precipitated powder from the precursor solution by hydrolysis crystallized to (gamma) phase, which was transformed to (beta) phase. The transformation temperatures of powders from (gamma) to (beta) phase of the ethoxide system and the boroxane system were 600 and 680 degree(s)C, respectively. The calcination of precursor films in a H 2 O-O 2 gas mixture was found to be effective for the decrease of crystallization temperature of (beta) -BBO films on Pt sheets. The precursor films prepared from the ethoxide system and the boroxane system crystallized to (Beta) -BBO on Pt(111)/glass substrates at 500 and 550 degree(s)C, respectively. The BBO films on Pt(111)/glass substrates showed c-axis preferred orientation. The (Beta) -BBO films on Pt(111)/glass substrates showed the second harmonic generation (SHG) of the intense 532 nm light on irradiation with 1064 nm Nd:YAG laser. The efficiency of SHG for the BBO films was also estimated.