LaGaO_3基固体电解质相变的Raman光谱研究

STUDY ON PHASE TRANSITIONS IN DOPED LaGaO_3 PEROVSKITE BY RAMAN SPECTROSCOPY

用Raman光谱研究了温度和掺杂物浓度对SrO和MgO掺杂LaGaO3固体电解质晶体结构的影响。结果表明 :增加掺杂物浓度以及升高温度都将增加LaGaO3本体结构的对称性。SrO/MgO复合掺杂和MgO单一掺杂的LaGaO3具有菱方钙钛矿结构 ,而单一掺杂SrO和未掺杂的LaGaO3具有斜方钙钛矿结构。在 15 0℃附近观察到了LaGaO3从斜方转变成赝三方结构的相变过程 ,而复合掺杂LaGaO3的结构对称性随温度的升高也有所增加。此外 ,在掺杂LaGaO3的Raman光谱中 ,在 5 2 0 ,75 0 ,810cm- 1 附近观察到了新的非本征吸收峰 。

Crystal structure of SrO and MgO doped LaGaO 3 was investigated by Raman spectroscopy. The effects of temperature and dopant concentrations on the structural symmetry were examined. Experimental results reveal that the LaGaO 3 crystals doped with SrO and MgO and with MgO only have rhombohedral structure, while doped with SrO have orthorhombic structure. A phase transition from orthorhombic to rhombohedral is found in pure LaGaO 3 at around 150 ℃, and at the same time the enhancement of the crystal symmetry is detected in the doubly doped LaGaO 3 as the temperature increased. New Raman bands at 520 cm -1 ,750 cm -1 and 810 cm -1 are found in the doped LaGaO 3 crystals, which may be resulted from the formation of oxygen vacancies in the system.