Effect of oxygen partial pressures on the growth of oxide single crystals by the floating zone method

This review deals with effects of oxygen partial pressures on the crystal growth of oxides containing transition elements. Rutile (TiO_2) and chromium-doped forsterite (Cr: Mg_2SiO_4) single crystals are successfully grown by the floating zone method. Rutile single crystals are grown under a low oxygen partial pressure of about 10^3 Pa to avoid the formation of low-angle grain boundaries. Zirconium-doping is effective to grow rutile single crystals without low-angle grain boundaries and bubble inclusions at a high growth rate of 10 mm/h under a high oxygen partial pressure of 10^5 Pa. Cr^-rich Cr: Mg_2SiO_4 single crystals are grown under a high oxygen partial pressure of 1-2 10^5 Pa, which can not be realized in the conventional Czochralski method using an iridium crucible.