采用溶胶凝胶法通过较低温度、较短的烧结时间制备了单相的多晶钙钛矿Pr_(0.75)Na_(0.25)Mn_(1-x)Fe_xO_3(0≤x≤0.3),避免了Na元素的挥发及锰氧化物的析出,使Pr_(1-x)Na_xMnO_3中Na的最大掺入量由文献报道的0.19提高到0.25,样品单相性得到大幅度提高.系列样品的磁化强度、电阻率随温度的变化关系表明2%的Fe掺杂便能大大减弱低温电荷有序;在x≤0.05时系列样品磁化强度随Fe含量的增加而增加,电阻率随Fe含量的增加而下降,然后二者随Fe含量进一步增加均朝相反的趋势变化.用几何效应(Fe~(3+)的几何尺寸大小)和电子结构的影响两个方面的竞争解释这种现象.
The single-phase polycrystalline perovskites Pr_(0. 75)Na_(0.25)Mn_(1-x)Fe_xFe_rO_3 (0 ≤ x≤0. 30) were prepared for the first time by a sol-gel technique, which offers shorter sintering time and lower temperature to avoid the volatilization of Na and the precipitation of manganese oxide. As a result, the maximum sodium solubility in Pr_(1-x) Na_xMnO_3 was improved from 0. 19 as the literature report to 0. 25, and the degree of single-phase was significantly improved. The temperature dependence of magnetization and resistivity of the samples series exhibits that long-range CO is disrupted even for 2% Fe doping level. The magnetization increases and resistivity decreases with increasing Fe doping for x≤0. 05, and then both of them vary to opposite tendency with further increasing Fe doping. The effects of Fe doping on Pr_(0.75)Na_(0.25)Mn_(1-x)Fe_xO_3 compounds can be analyzed from the competition of two different aspects, namely the geometric effect (size of the dopant) and electronic configurations.
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