In order to elucidate the effects of Ba doping in a silica crucible used for growing Czochralski Si (CZ-Si) crystals, in situ observations and differential scanning calorimetry (DSC) measurements were employed for investigating the reaction at the interface between the Si melt and the Ba-doped silica glass. It was found that the generation of a so-called brownish ring was suppressed completely by Ba doping when the Ba concentration in the silica glass was higher than 30 ppm. Ba doping in the silica glass increased the formation rate of white cristobalite crystallized by phase transition directly from the silica glass, which counteracted the growth of the brownish rings and suppressed their amount. A decrease in the activation energy for the crystallization of cristobalite by Ba doping was verified by means of the DSC measurements, which caused an increase in the growth rate of the white cristobalite. (c) 2007 Elsevier B.V. All rights reserved.