BETA-BARIUM BORATE SINGLE-CRYSTAL GROWN BY A DIRECT CZOCHRALSKI METHOD

High purity single-crystal of beta-BaB2O4 has been successfully grown from a BaB2O4 melt with the direct Czochralski method. The obtained crystal was confirmed to be that of the low-temperature beta-phase by powder X-ray diffraction and the second harmonics generation. The growth rate was 0.6 mm/h, which is more than ten times as large as that in the flux method. The growth direction was [001]. The present method requires to satisfy several important factors, such as choice of the starting material and temperature gradient at the growing point. The reason why a crystal of the low-temperature form is grown directly from a melt of the compound can be explained by the Ostwald step rule.