Raman spectroscopic study of structural changes in calcium aluminate (CaAl2O4) glass at high pressure and high temperature
Raman spectroscopic study of structural changes in calcium aluminate (CaAl2O4) glass at high pressure and high temperature
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DOI：
10.1016/0009-2541(95)00159-x
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发表时间：
1996-06-07
期刊：
影响因子：
3.9
通讯作者：
Poe, BT
中科院分区：
文献类型：
--
作者：
Daniel, I;McMillan, PF;Poe, BT
在室温至15 GPa和室温至1650 K范围内，获得了铝酸钙（CaAl 2 O 4）玻璃的拉曼光谱随压力的变化曲线。在300 K的压力增加时，拉曼光谱在8和10 GPa之间急剧变化。整个光谱的强度减弱，580-cm（-1）带的强度显著降低，并且以750 cm（-1）附近为中心的新宽带开始占主导地位。我们解释这些光谱变化是由于形成高度协调的铝物种通过参与桥氧（即形成O-[3]物种）。减压时，压力引起的光谱变化大多是可逆的。然而，减压样品不完全放松到正常的环境状态，光谱反映了重要的变化，四面体间AlOAl联系。这些变化是一致的一些高坐标物种被保留在减压样品。在室温下通过玻璃转变范围（Tg = 1178 K）的温度增加，我们的拉曼光谱显示出重要的构型变化的证据，振动效应被删除后。主要的光谱变化包括600和1100 cm（-1）之间的宽带的增长，出现在T-g之上。我们认为，这些构型变化涉及从完全聚合的铝酸盐框架中去除O2-离子，从而在高温下形成O-[3]物种（“三簇”），由三个四面体铝酸盐基团协调。
The Raman spectrum of calcium aluminate (CaAl2O4) glass has been obtained as a function of pressure at ambient temperature to similar to 15 GPa, and as a function of temperature at room pressure to 1650 K. On increasing pressure at 300 K, the Raman spectrum changes drastically between 8 and 10 GPa. The intensity of the overall spectrum weakens, the intensity of the 580-cm(-1) band decreases markedly, and a new broad band centered near 750 cm(-1) begins to dominate the spectrum. We interpret these spectral changes as due to the formation of highly coordinated Al species through the involvement of bridging oxygens (i.e. formation of O-[3] species). Upon decompression, the pressure-induced spectral changes are mostly reversible. However, the decompressed samples do not relax completely to their normal ambient state, and the spectra reflect important changes in the inter-tetrahedral AlOAl linkages. These changes are consistent with some high-coordinate species being retained in the decompressed sample. On increasing temperature through the glass transformation range (T-g = 1178 K) at room pressure, our Raman spectra show evidence for important configurational changes, after vibrational effects are removed. The major spectral change consists of growth of a broad band between 600 and 1100 cm(-1), appearing immediately above T-g. We suggest that these configurational changes concern the removal of O2- ions from the fully polymerized aluminate framework, with the resulting formation at high temperature of O-[3] species (''triclusters''), coordinated by three tetrahedral aluminate groups.