为了进一步提高La-Ca-Mn-O体系巨磁阻陶瓷的转变温度,利用固相反应法制备了La_(0.67)Ca_(0.33)MnO_3巨磁阻陶瓷柱状(φ13 mm×8 mm)样品,研究了不同切型对转变温度的各向异性的影响.通过R-T曲线测量发现沿与样品压力轴垂直和平行的方向切割制成的样品,在零磁场和施加0.5 T的磁场强度时转变温度均相差80 K.利用XRD和SEM研究了样品的相结构和微观结构,初步解释了转变温度差异的机理.
In order to further enhance resistance transition temperature (Tp) of metal-semiconductor of La-Ca-Mn-O colossal magnetoresistance ceramics, La_(0.67)Ca_(0.33)MnO_3 (LCMO) polycrystalline ceramics were formed as cylindrical pellets (φ13 mm×8 mm) by conventional solid-state reaction method. The anisotropy of LCMO samples which was cut from the sections parallel and perpendicular to the pressing direction were studied, respectively. The R-T curves shows that transition temperatures for these two types of specimens were 177 K and 261 K, respectively under null and 0.5 T magnetic field. In addition, the mechanism of dramatic enhancement of transition temperature was explained through investigating XRD and SEM of the specimens.
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