A stability of Ba(B0.9Al0.1)(2)O-4 molten zone was investigated for a containerless process by a modified floating-zone technique under a normal gravity condition on the ground. In this technique, a pair of Pt tubes was used at an upper and a lower position. It was difficult to form a long and stable molten zone using a pair of Pt tubes with the same diameter due to the gravity. On the other hand, a long and a stable molten zone was formed using a large diameter Pt tube at the upper position. The length of the molten zone was enough for the containerless process.