The crystal structure of the composite crystal Ca_0.83CuO₂ was investigated by synchrotron powder diffraction at high temperature. The incommensurate modulated structure was firstly analyzed at room temperature (RT) and successfully solved by adopting the (3D + 1)-dimensional symmetry P2₁/m(α0γ)0s. The composite crystal is featured by a non-uniform distribution of Ca ions occupying octahedral sites formed by the spatial arrangement by the infinite 1D CuO₂ chains. By approaching 500 K, Ca_0.83CuO₂ undergoes a structural rearrangement ruled by the shrinking of the Ca interatomic distances. The high-temperature crystalline phase is characterized by a different incommensurate periodicity requiring the recombination of the Ca/CuO₂ balance featuring the composite intergrowth of the two almost independent sub-structures. We ascertain that the new crystalline form is stable up to 950 K near to the limit of the thermal decomposition.

中文翻译：

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复合晶体Ca0.83CuO2的高温演化

通过高温下的同步加速器粉末衍射研究了Ca _0.83 CuO ₂复合晶体的晶体结构。首先在室温（RT）下分析了不等价的调制结构，并通过采用（3D +1）维对称性P2 ₁ / m（α0γ）0s成功地解决了这一问题。复合晶体的特征是，Ca离子分布不均匀，占据了无限的一维CuO ₂链通过空间排列形成的八面体位置。接近500 K时Ca _0.83 CuO ₂Ca原子间距的缩小导致结构发生重排。高温结晶相的特征在于不同的不规则周期，需要重新组合Ca / CuO ₂平衡，以两个几乎独立的子结构的复合共生为特征。我们确定，在接近热分解极限的情况下，新的晶型在950 K下都稳定。