Institute for High Pressure Physics RAS, 142190 Troitsk Moscow region, Russia.
Phys Rev Lett. 2010 Sep 10;105(11):115701. doi: 10.1103/PhysRevLett.105.115701. Epub 2010 Sep 9.
Liquid B2O3 represents an archetypical oxide melt with a superhigh viscosity at the melting temperature. We present the results of the in situ x-ray diffraction study and the in situ viscosity measurements of liquid B2O3 under high pressure up to 8 GPa. Additionally, the 11B solid state NMR spectroscopy study of B2O3 glasses quenched from the melt at five different pressures has been carried out. Taken together, the results obtained provide understanding of the nature of structural transformations in liquid B2O3. The fraction of the boroxol rings in the melt structure rapidly decreases with pressure. From pressures of about 4.5 GPa, four-coordinated boron states begin to emerge sharply, reaching the fraction 40%-45% at 8 GPa. The viscosity of the B2O3 melt along the melting curve drops by 4 orders of magnitude as the pressure increases up to 5.5 GPa and remains unchanged on further pressure increase.
液态 B2O3 代表一种典型的氧化物熔体，在熔点时具有超高的粘度。我们呈现了在高达 8 GPa 的高压下对液态 B2O3 进行原位 X 射线衍射研究和原位粘度测量的结果。此外，我们还对从熔体在五个不同压力下淬火的 B2O3 玻璃进行了 11B 固态 NMR 光谱研究。综合这些结果，我们对液态 B2O3 中结构转变的性质有了更深入的理解。熔体结构中硼氧环的分数随着压力的增加迅速减少。从约 4.5 GPa 的压力开始，四配位硼的状态开始急剧出现，在 8 GPa 时达到 40%-45%的分数。随着压力从 5.5 GPa 增加到 8 GPa，B2O3 熔体的粘度沿熔化曲线下降了 4 个数量级，而在进一步增加压力时保持不变。
