Single phase, electrically insulating, multiferroic La-substituted BiFeO3 prepared by mechanosynthesis
Single phase, electrically insulating, multiferroic La-substituted BiFeO3 prepared by mechanosynthesis
复制标题
DOI：
10.1039/c4tc01426j
复制
发表时间：
2014-09
影响因子：
6.4
通讯作者：
A. Perejón;P. E. Sánchez-Jiménez;L. Pérez-Maqueda;J. Criado;J. R. D. Paz;R. Sáez-Puche;N. Masó
中科院分区：
文献类型：
--
作者：
A. Perejón;P. E. Sánchez-Jiménez;L. Pérez-Maqueda;J. Criado;J. R. D. Paz;R. Sáez-Puche;N. Masó
首次采用机械合成法在全成分范围内制备了单相电绝缘的Bi1-−_xLa_xFeO_3固溶体样品。La的取代影响了机械力化学反应的动力学和产物的微晶尺寸。对于0≤x≤0.15，La含量的增加导致获得最终产品所需的重量归一化累积动能显著降低，所得到的微晶尺寸增加。较大的La含量对反应活性和微晶尺寸均无影响。已经确定了x对结构的影响。在x≤0.15和x≥0.45范围内，样品分别具有R3c和Pnma空间群的单相固溶体，而在中间范围内，获得了非中心对称的Pn21a(00γ)s00超结构。对于0≤x≤0.30，差示扫描量热仪显示了与Neel温度(TN，反铁磁-顺磁转变)和居里温度(TC，铁电-顺电转变)相对应的两个吸热效应，显示了它们的多铁性。La含量较大的成分只有TN。膨胀和介电常数测量证实了DSC对铁电-顺电转变的结果。Tn和Tc的组成依赖关系表明，在低x时，Tn<；Tc，但当Tn=Tc=386°C时，在x∼=0.28时发生了交叉或等铁转变，0≤x≤为0.15的陶瓷在室温下具有很高的绝缘性，由Arrhenius曲线推算的电阻率为∼7×10~(16)~8×10~(14)Ωcm，激活能∼为1.14~1.20 eV。La掺杂提高了样品的磁化强度。
Single phase, electrically insulating samples of Bi1−xLaxFeO3 solid solutions have been prepared by mechanosynthesis over the whole compositional range for the first time. Lanthanum substitution influenced the kinetics of the mechanochemical reaction and crystallite size of the products. For 0 ≤ x ≤ 0.15, an increase in the La content produced a significant decrease in the weight-normalized cumulative kinetic energy required to obtain the final product and an increase in the resulting crystallite size. Larger La contents did not affect either the reactivity or the crystallite size. The effect of x on the structure has been identified. Samples in the ranges x ≤ 0.15 and x ≥ 0.45 gave single phase solid solutions with R3c and Pnma space groups, respectively, while for the intermediate range, a non-centrosymetric Pn21a(00γ)s00 super structure was obtained. For 0 ≤ x ≤ 0.30, differential scanning calorimetry showed two endothermic effects corresponding to the Neel temperature (TN, antiferromagnetic–paramagnetic transition) and the Curie temperature (TC, ferroelectric–paraelectric transition), demonstrating their multiferroic character. Compositions with a larger La content only showed TN. Dilatometric and permittivity measurements confirmed the results obtained by DSC for the ferroelectric–paraelectric transition. The composition dependence of TN and TC showed that, at low x, TN < TC, but a cross-over, or isoferroic transition occurred at x ∼0.28, when TN = TC = 386 °C. Ceramics with 0 ≤ x ≤ 0.15 were highly insulating at room temperature with a resistivity, extrapolated from the Arrhenius plots, of ∼7 × 1016 to 8 × 1014 Ω cm and an activation energy ∼1.14–1.20 eV. Magnetization of the samples improved with La substitution.