DENSITY-DRIVEN LIQUID-LIQUID PHASE-SEPARATION IN THE SYSTEM AL2O3-Y2O3
DENSITY-DRIVEN LIQUID-LIQUID PHASE-SEPARATION IN THE SYSTEM AL2O3-Y2O3
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DOI：
10.1038/369633a0
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发表时间：
1994-06-23
期刊：
影响因子：
64.8
通讯作者：
MCMILLAN, PF
中科院分区：
文献类型：
--
作者：
AASLAND, S;MCMILLAN, PF
将液体混合物相分离成具有不同组成的两种液体是众所周知的现象。有人提出（1-9），在某些元素体系中可能发生另一种类型的液-液相分离，这种分离是由密度波动而不是成分波动驱动的。对于单组分氧化物H2O、SiO2和GeO 2，已经描述了低密度和高密度非晶相之间的转变（参考文献10-17），并且已经提出（参考文献18-21）在过冷水中可能发生液-液相变。如果密度驱动的相分离确实发生在液体混合物中，那么应该可以观察到两种具有相同组成但不同密度的液体的共存。在这里，我们报告了对这种情况的直接观察。我们观察到两个共存的液相在过冷熔体的Al 2 O3-Y2 O3刚刚高于玻璃化转变在环境压力下，这两个具有相同的组成。我们建议，这两个阶段必须不同的唯一密度，和过渡是熵驱动。该系统中相变的发生可以解释为什么钇铝石榴石（YAG激光器中Nd 3+离子的基质材料）的结晶缓慢（22-25）。
Phase separation of liquid mixtures into two liquids with different compositions is a well-known phenomenon. It has been proposed(1-9) that another type of liquid-liquid phase separation, driven by fluctuations in density rather than in composition, may occur in some elemental systems. Transitions between low- and high-density amorphous phases have been described for the one-component oxides H2O, SiO2 and GeO2 (refs 10-17), and it has been suggested(18-21) that a liquid-liquid phase transition might occur in supercooled water. If density-driven phase separation truly does occur in liquid mixtures, it should be possible to observe the coexistence of two liquids with the same composition but different density. Here we report the direct observation of such a situation. We observe two coexisting liquid phases in the supercooled melt of Al2O3-Y2O3 just above the glass transition at ambient pressure, both of which have the same composition. We propose that these two phases must differ solely in density, and that the transition is entropically driven. The occurrence of the phase transition in this system may explain why the crystallization of yttrium aluminium garnet, the host material for Nd3+ ions in YAG lasers, is sluggish(22-25).