Crystal growth of SnO2 and other MO2 (M = Ti,Zr, Hf) oxides by flux of B2O3?V2O5 system

Single crystals of SnO₂ and MO₂ (M = Ti, Zr, Hf) oxide were grown from flux of B₂O₃? V₂O₅ system. Mixtures of the flux and the starting powder of Zn₂SnO₄, TiO₂, ZrO₂, or HfO₂ were soaked at a temperature of 1030–1340°C for 10–72 hr and then were cooled down to 900°C at a rate of 5°C/hr. Grown crystals of SnO₂ were pale brown needles. An increase in V₂O₅ content of the flux (up to V₂O₅/B₂O₃ ratio equal to 2) or in the soaking temperature increases the crystal size. A largest crystal with the size of 15.0 × 0.4 × 0.4 mm was obtained in the case of V₂O₅/B₂O₃ = 2. Crystals of TiO₂ were black needles or platelets, and those of ZrO₂ and HfO₂ were yellowish, transparent needles or blocks. The maximum size of TiO₂, ZrO₂ or HfO₂ crystal was 12.0 × 0.1 × 0.1 mm, 4.0 × 0.3 × 0.3 mm or 11.0 × 0.6 × 0.6 mm, respectively. The long axis of the crystals was all C-axis and main faces on the crystals were of {100} and/or {110} families. All these crystals were found to include the impurities of boron and vanadium. The electrical resistivities of SnO₂ and TiO₂ crystals were measured to be 1.4 × 10⁶ and 5.6 × 10⁴ Ω · cm at 25°C, respectively.