采用溶胶-凝胶法制备了系列La0.8-xCa0.2MnO3多晶样品，用X射线衍射分析确定了样品的钙钛矿结构，用透射电子显微镜观察了样品的形貌及粒径分布情况，用PAR155型振动样品磁强计测量了样品的磁性随外场和温度的变化，确定样品的居里温度并计算了各样品的磁熵变. 磁测量及计算结果表明制备的各样品的居里温度在180—260K的范围内且随焙烧温度和La3+离子空位浓度的不同而变化，不同温度焙烧的样品均有较大的磁熵变值，其中1100℃焙烧的La0.77Ca0.2MnO3，多晶样品在240.5K，H=1.0T的外场下的磁熵变达3.76J/kg·K，对实验结果做了定性的分析. 该材料具有较高的居里温度和较大的磁熵变，所需外场强度适中，电阻率高，性能稳定，适合做高温磁制冷材料.%Polycrystalline samples of La0.8-xCa0.2MnO3(x=0，0.01，0.03，0.05，0.08，0.1) were synthesized using a sol-gel technique. Structure analysis, morphology observation and magnetic measurement have been used to study the effect of vacuum concentration of La3+ on the Curie temperature and magnetic entropy change of La0.8-xCa0.2MnO3. The experimental results show that by tuning the vacuum concentration of La3+, the materials could exhibit very different Curie temperatures (from 180 to 260K). All the samples in this paper have large magnetic entropy change, especially for La0.77Ca0.2MnO3 sintered at 1100℃, which has a very large magnetic entropy change ΔSM=3.76J/kg·K under the magnetic field H=1.0T. The phenomenon of large magnetic entropy change, high Curie temperature, high electrical resistivity and high chemical stability make this material a suitable candidates for refrigerants at high temperature.
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