发表机构
Ames National Laboratory, U.S. Department of Energy, Iowa State University; Indian Institute of Technology Delhi; The University of New South Wales (UNSW)（艾姆斯国家实验室，美国能源部，爱荷华州立大学; 德里印度理工学院; 新南威尔士大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过拉曼光谱与XRD结合，解耦了SrLaCoNbO6中八面体畸变与对称性破缺相变，为复杂双钙钛矿的结构分析提供了无需同步辐射的稳健方法。
AI 中文摘要
我们利用拉曼光谱和X射线衍射（XRD）相结合的方法，在25–900~$^\circ$C的温度范围内，对B位有序双钙钛矿SrLaCoNbO$_6$进行了全面的高温结构研究。通过声子频率和线宽的显著重整化，以及特征XRD反射的演变和抑制，我们确定了两个不同的温度驱动异常，分别位于$T_\mathrm{OD} = 300\pm 25~^\circ$C和$T_\mathrm{PT} = 750\pm 25~^\circ$C。在$T_\mathrm{OD}$处的低温异常与单斜$P2_1/n$相内的等结构八面体畸变有关。在$T_\mathrm{OD}$处，CoO$_6$和NbO$_6$八面体的径向和角向畸变参数降至接近零值，随后由于面内Co–O和Nb–O键长层级反转，在进一步加热时又发生逆转。在$T_\mathrm{PT}$处的高温异常对应于从$P2_1/n$到单斜$I2/m$相的对称性破缺结构相变，这一点通过群论分析和Rietveld精修得到了确认。这些结果表明，将温度依赖的拉曼光谱与实验室XRD相结合，并辅以定量八面体畸变分析，为在复杂双钙钛矿氧化物中解耦等结构八面体畸变与对称性破缺相变提供了一种稳健的方法，且无需借助同步辐射或中子衍射设施。
英文摘要
We report a comprehensive high temperature structural investigation of the B-site ordered double perovskite SrLaCoNbO$_6$ using combined Raman spectroscopy and x-ray diffraction (XRD) over the range 25--900~$^\circ$C. Two distinct temperature-driven anomalies are identified at $T_\mathrm{OD} = 300\pm 25~^\circ$C and $T_\mathrm{PT} = 750\pm 25~^\circ$C through pronounced renormalizations in the phonon frequency and linewidth, accompanied by the evolution and suppression of characteristic XRD reflections. The low-temperature anomaly at $T_\mathrm{OD}$ is associated with an isostructural octahedral distortion within the monoclinic $P2_1/n$ phase. At $T_\mathrm{OD}$, the radial and angular distortion parameters of the CoO$_6$ and NbO$_6$ octahedra decrease to near-zero values before reversing upon further heating due to an inversion of the in-plane Co--O and Nb--O bond-length hierarchy. The high-temperature anomaly at $T_\mathrm{PT}$ corresponds to a symmetry-breaking structural phase transition from $P2_1/n$ to the monoclinic $I2/m$ phase, confirmed by group-theoretical analysis and Rietveld refinement. These results demonstrate that integrating temperature-dependent Raman spectroscopy with laboratory-based XRD, complemented by quantitative octahedral distortion analysis, provides a robust approach to disentangle isostructural octahedral distortions from symmetry-breaking phase transitions in complex double perovskite oxides without recourse to synchrotron or neutron diffraction facilities.
