A series of double-perovskite oxides Sr₂Sr_1-xCa_xTeO₆ (0 ≤ x ≤ 1) samples have been prepared in order to study the effect of composition on phase formation and the related optical properties. The objective of this work is to study the possibility of calcium insertion with different percentages since calcium in known to enhance the electrical properties. In this work a well detailed structure and phase transitions investigation of the compounds were conducted and probed by X-ray diffraction and Raman spectroscopy techniques at room temperature. Both Rietveld refinements and Raman studies revealed that two phase transitions took place as the calcium amount x increases; a first from a triclinic to a hexagonal in the range 0.1 < x < 0.25 and a second from the hexagonal to a monoclinic structure in the range 0.5 < x < 0.6. The optical absorption α(λ) was also determined as a function of calcium content in the series samples using UV-vis analysis. It was revealed that a remarkable change occured in the cut-off wavelength, confirming the sequence of phase transitions C1 → R\( \overline{3} \)m → P2₁/n. The optical band gap measurements showed that the triclinic Sr₃TeO₆ and the monoclinic Sr₂CaTeO₆ phases have band gap values of 2.75 and 2.81 eV, respectively. When the calcium increased to x = 0.25 (Sr_2.75Ca_0.25TeO₆)_, remarkable decrease of the band gap value was observed, with Eg = 2.627 eV.

一系列双钙钛矿氧化物Sr ₂ Sr _1-x Ca _x TeO ₆为了研究组成对相形成和相关光学性质的影响，已制备了（0≤x≤1）样品。这项工作的目的是研究钙以不同百分比插入的可能性，因为已知钙会增强电性能。在这项工作中，对化合物进行了详细的结构和相变研究，并在室温下通过X射线衍射和拉曼光谱技术进行了探测。Rietveld精炼和拉曼研究都表明，随着钙含量x的增加，发生了两个相变。第一个从三斜结构到六边形，范围为0.1 <x <0.25，第二个从六边形结构到单斜结构，范围为0.5 <x <0.6。还使用紫外可见分光光度法测定了系列样品中的光吸收α（λ）与钙含量的关系。揭示了截止波长发生了显着变化，证实了相变C的顺序1  →  R \（\ overline {3} \）m  →P 2 ₁ / n。光学带隙测量表明三斜Sr ₃ TeO _6相和单斜Sr ₂ CaTeO ₆相的带隙值分别为2.75和2.81 eV。当钙增加到x = 0.25（Sr _2.75 Ca _0.25 TeO ₆）时_，带隙值显着下降，Eg = 2.627 eV。