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ll921(金币+15, 翻译EPI+1): 2011-03-08 20:15:07
When a pure oxygen atmosphere was applied, bubbles were observed in the melt, which resulted in an unstable molten zone. And the molten zone was more stable in an air atmosphere. In addition, a higher lamp power resulted that more liquid (could) be replenished from the melting feed rod than (that would) be crystallized. So a stable floating zone was achieved by lowering the lamps power to 62.1 % in the air flow of 0.1 L/min and the pressure of 0.1 MPa. xxx crystals were grown by spontaneous nucleation. When growth began, multiple nucleation sites were observed to form. After some optimizations, the as-grown rod (was,删除） composed of several large domains as shown in Fig. 1 a. It （could） be seen that the as-grown sample (was) dark-brown cylindrical rod of 4-6 mm in diameter and 87 mm in length. The largest crystal domain was Ф 5 mm× L 32 mm. The dark brown color in as-grown crystal could be attributed to the partial reduction of Nb5+ ions, which was a common problem with alkali-earth niobates grown directly from their melts [15, 17]. And Fig. 1 b (showed) the crystal wafer cut parallel to the growth direction, then annealed in an oxygen atmosphere at 1500 K for 10 h. The annealed wafer faded to light brownish.
The powder XRD pattern of the as-grown crystal (was) shown in Fig. 2. It （could） be found that all peaks could be indexed to the diffraction peaks for the xxx (Ref: PDF Number: 330875). It (indicated) that the as-grown crystal (was) columbite xxx without impurity phases. The powder XRD pattern of the annealed crystal was also measured and the peak positions and relative intensity were unchanged. It (indicated) that the annealing (had) no effect on the structure of the crystal. |
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