This study examines the properties of a titanium single crystal fabricated by the floating-zone-melting process in Ar gas flow atmosphere where the partial pressure of oxygen was maintained extremely low at P O2 ¼ $10 À23 atm by the newly developed oxygen pump system. The distribution of solute oxygen atoms in the obtained single crystal exhibited a peculiar gradient. In the early stage of the titanium single crystal growth, the oxygen content in the single crystal (approximately 1600 ppm) was higher than that in the mother ingot (980 ppm). However, as the crystal growth progressed, the oxygen content gradually decreases and then reduced to 660 ppm in the final stage of crystal growth. Such a gradient of oxygen composition was not detected in titanium single crystals fabricated under conventional, commercial Ar gas flow atmosphere. Owing to the unique gradient of oxygen content formed under extremely low oxygen partial pressure, the Vickers hardness of the single crystal decreased gradually along the crystal growth direction.

We report the single-crystal growth of the unconventional superconductor Sr2RuO4, on which research has reached a turning point recently. In order to optimize the quality of crystals grown by the floating-zone method using an infrared image furnace, we focus on an improvement of the structure of the filament in the halogen lamps. By reducing the thickness of the total filament, the form of the molten zone was narrowed. More importantly, the molten zone was observed to be more stable during the growth process. Finally, we obtained the crystals with a length of 12 cm. Additionally, the grown crystal has high quality, displaying the 1.5 K transition temperature expected only for the purest crystals. We also discuss the availability of the newly developed halogen lamps.

No abstract

In this study, we focused on the fabrication of titanium single crystal by the floating zone melting process under the Ar gas flow atmosphere where partial pressure of oxygen was kept to be extremely low around P O2 ＝10 -23 atm, by using the newly developed oxygen reduction system. In the obtained single crystal, distribution of solute oxygen atoms exhibited a peculiar gradient. In the portion gained in an early stage of the crystal growth, the oxygen content showed a higher value of about 1600 ppm than that in the mother ingot of 980 ppm. As the crystal growth proceeded, however, the oxygen content showed a gradual decrease, and in the final portion of the crystal growth, the oxygen content dropped down to 660 ppm. Such a gradient of oxygen composition was not detected in Ti single crystals fabricated under the standard and usual Ar gas flow condition. Owing to the unique gradient of oxygen content under extremely low oxygen partial pressure, the Vickers hardness in the single crystal showed a gradual decrease along the crystal growth direction. CaO およびフラックスを用いた脱酸法 4) ，電解法 5,6) ，新ヨ ウ化法 7) など種々の方法が提案，開発され，100 ppm を下回

No abstract