La0.67-xCa0.33MnO3系列样品的磁热效应

用溶胶-凝胶法制备了不同空位浓度掺杂的La0.67-xCa0.33MnO3系列样品(x=0.00,0.02,0.06,0.10),用扫描电子显微镜(SEM)观察了样品的形态和颗粒大小,X射线衍射实验结果显示样品为单相钙钛矿结构,用振动样品磁强计(VSM)测量了样品的磁化强度随温度变化的M-T曲线和起始磁化M-H曲线.研究了空位浓度对样品的居里温度Tc和磁熵变的影响.结果表明,空位浓度的掺杂将样品的居里温度Tc提高至室温附近,磁熵变得到增强.对于经历了一级相变的样品La0.67-xCa0 33MnO3(x=0.02),在居里温度Tc(277 K)附近和1T外磁场下,最大磁熵变达到了2.78 J/(kg·K).

Magnetocaloric effect of La$_{0.67-x}$Ca$_{0.33}$MnO$_{3}$

Polycrystalline samples of La$_{0.67-x}$Ca$_{0.33}$MnO$_{3}$($x$=0.00, 0.02, 0.06, and 0.10) with different vacancies in La$^{3+}$--sitewere prepared by sol--gel method. The grain sizes of samples were observedby SEM. XRD results show that the samples are single phase of perovskite--typeoxides. The Curie temperatures and the magnetic entropy change of the sampleswere studied by VSM. The influence of the vacancy concentration inLa$^{3+}$--site on their magnetocaloric properties has been investigated.The higher Curie temperatures close to room temperature and the largermagnetic entropy changes have been observed. The maximum magnetic entropychange, 2.78 J/(kg$cdot$K), is obtained near its Curie temperature (277 K) underthe field of 1 T for La$_{0.67-x}$Ca$_{0.33}$MnO$_{3}$ ($x$=0.02) sample.