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首页> 外文期刊>Journal of Materials Chemistry, A. Materials for energy and sustainability >In situ high temperature powder neutron diffraction study of undoped and Ca-doped La_(28-x)W_(4+x)O_(54+3X/2) (x = 0.85)
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In situ high temperature powder neutron diffraction study of undoped and Ca-doped La_(28-x)W_(4+x)O_(54+3X/2) (x = 0.85)

机译：未掺杂和掺Ca的La_（28-x）W_（4 + x）O_（54 + 3X / 2）的原位高温粉末中子衍射研究（x = 0.85）

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摘要

In situ neutron diffraction experiments of 2% Ca-doped and nominally undoped lanthanum tungstate (La_(28-x)W_(4+x)O_(54+3X/2) with x = 0.85) have been carried out under controlled pD2Oand pO2 at elevated temperatures. All the diffraction patterns could be refined using an average cubic fluorite-related structure, in accordance with recent reports. The material exhibits disorder of the oxygen and the cation sublattices. Splitting of the oxygen sites around tungsten from the 32f to 96k Wyckoff position in the Fm3m space group improves the model and can better represent the oxygen disorder. No phase transition was detected from room temperature up to 800 °C under any of the studied conditions. Expansion of the unit cell constants in the presence of water at intermediate and low temperatures was correlated with the formation of protonic defects. The thermal expansion coefficient for lanthanum tungstate is rather linear under all studied conditions (~11 × 10~(-6) K~(-1)). The in situ diffraction studies are correlated with dilatometry investigations and conductivity measurements.
机译：在受控pD2O和pO2的控制下，进行了2％的掺杂Ca和名义上未掺杂的钨酸镧（La_（28-x）W_（4 + x）O_（54 + 3X / 2），x = 0.85）的原位中子衍射实验。在高温下。根据最近的报道，所有的衍射图样都可以使用平均立方萤石相关结构进行细化。该材料表现出氧和阳离子亚晶格的紊乱。在Fm3m空间群中，钨周围的氧位点从32f Wyckoff位置分裂到96k Wyckoff位置改善了模型，可以更好地表示氧紊乱。在任何研究的条件下，从室温到800°C都没有检测到相变。在中，低温水存在下，晶胞常数的膨胀与质子缺陷的形成有关。钨酸镧的热膨​​胀系数在所有研究条件下（〜11×10〜（-6）K〜（-1））都相当线性。原位衍射研究与膨胀学研究和电导率测量相关。

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