采用溶胶-凝胶法制备了(Pr1-xLax)0.75Na0.25MnO3(0.00≤x≤1.00) 系列多晶样品. X射线衍射结果表明, 所有样品均为单相类钙钛矿结构, 随着La3+离子含量的增加, 样品由x≤0.50时的正交结构转变为x≥0.70时的菱面体结构．磁性测量结果表明, La3+离子的掺入还导致了Pr0.75Na0.25MnO3电荷有序的破坏. 在x≤0.1时, 电荷有序转变温度随La3+离子含量增加而降低; 当x≥0.10时, 电荷有序现象消失, 样品出现顺磁-铁磁相变, 同时伴随着绝缘体--金属转变．磁熵变研究表明, x≥0.5的样品在室温附近和较低磁场下具有较大的磁熵变, 可望成为新的室温磁致冷材料.
Polycrystalline (Pr 1-x La x)0.75Na0.25MnO3 (0.00≤x≤1.00) manganites were prepared by sol-gel method. X-ray Diffraction patterns showed that the samples are crystallized in single phase with perovskite-like structure. The structure of the compounds transforms from orthorhombic structure for x≤0.50 to rhombohedral structure for x≥0.70. The introduction of La3+ ions also suppresses the charge ordering in the samples. The charge ordering transition temperature decreases with increasing La3+ doping when x≤0.10. The charge ordering phenomenon disappeared for the samples with x＞0.10, paramagnetic-ferromagnetic transition appeared, while the insulator-metal transition can be observed. For x≥0.50, the compounds also show large magnetic entropy change under low field near or above room temperature, indicating the material can be used in magnetic refrigeration.
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| [1] | |
| [2] | |
| [3] | |
| [4] | |
| [5] | |
| [6] | |
| [7] |
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