The preparation of In2O3 crystals in phase separated structure of sodium borosilicate (Na2O-B2O3-SiO2) glass was successfully obtained by melt quenching method and its electrical conductivity was successfully clarified. Sodium borosilicate glass is phase separated into silica (SiO2) phase and sodium borate phase (Na2O-B2O3). The sodium borate phase mainly contains ionic bondings, and the generation and growth of crystals can easily occur in this phase for its high solubility of various kinds of ions. In this study, a glass ceramics was prepared by precipitating In2O3 crystals in the sodium borate phase of the sodium borosilicate glass. After acid leaching of the sodium borate phase, the In2O3 X-ray diffraction peaks that were observed after crystallization treatment disappeared, indicating that In2O3 crystals were selectively precipitated in the sodium borate phase. By decreasing the proportion of the sodium borate phase which was achieved via controlling the amount of B2O3 in the glass, In2O3 crystals precipitated continuously in this phase, resulting in an increase in the electrical conductivity from 3.30 x 10(-5) S/cm to 6.56 x 10(-5) S/cm at 500 degrees C and a decrease in the activation energy from 36.6 kJ/mol to 27.0 KJ/mol, respectively. Furthermore, the electrical conductivity increased by Sn doping and introduction of oxygen vacancies via H-2 reduction into the In2O3 crystal lattice. (C) 2017 Elsevier Ltd. All rights reserved.