Structure, phase diagram and magnetic properties of Bi<sub>1−xsub>La<sub>xsub>FeO<sub>3sub> solid solution

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• 作者：Q.R. Yao<sup>asup><sup> ; sup><sup>bsup><sup> ; sup><sup>csup><sup> ; sup><sup>qingry96@guet.edu.cn" class="auth_mail" title="E-mail the corresponding authorsup> ; Y.H. Shen<sup>bsup> ; P.C. Yang<sup>bsup> ; H.Y. Zhou<sup>bsup><sup> ; sup><sup>csup> ; G.H. Rao<sup>bsup><sup> ; sup><sup>csup> ; Z.M. Wang<sup>bsup><sup> ; sup><sup>csup> ; J.Q. Deng<sup>bsup><sup> ; sup><sup>csup>
• 关键词：C. Magnetic properties ; Phase diagram ; Phase transition ; X-ray diffraction ; Crystal structure
• 刊名：Ceramics International
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：42
• 期：5
• 页码：6100-6106
• 全文大小：2426 K

文摘

A series of polycrystalline Bi<sub>1&minus;m>xm>sub>La<sub>xsub>FeO<sub>3sub> (0≤m>xm>≤1.00) solid solution were synthesized by sol–gel method. The effects of lanthanum concentration on the phase formation, phase transition and magnetic properties were studied. The XRD results displayed that there is a clear indication of structural modification and symmetry change brought about by La doping. At room temperature the crystal structure of the solid solution transforms from rhombohedral R3c (m>xm>≤0.15) to tetragonal P4mm (0.15<m>x  m><0.40), then to cubic mmlsi0002" class="mathmlsrc">mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0272884216000031&_mathId=si0002.gif&_user=111111111&_pii=S0272884216000031&_rdoc=1&_issn=02728842&md5=34ed39e41f75ed0c199a5c6d58e8dd4f">mg class="imgLazyJSB inlineImage" height="15" width="44" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0272884216000031-si0002.gif">mathContainer hidden">mathCode"><math altimg="si0002.gif" overflow="scroll"><mrow><mi>Pmi><mi>mmi><mover accent="true"><mn>3mn><mo>&macr;mo>mover><mi>mmi>mrow>math> (0.40≤m>xm><0.50), and finally to orthorhombic Pbnm (0.50≤m>x  m>≤1.00). In situ high temperature X-ray powder diffraction studies reveal that phase transformations of the rhombohedral R3c and the cubic mmlsi0002" class="mathmlsrc">mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0272884216000031&_mathId=si0002.gif&_user=111111111&_pii=S0272884216000031&_rdoc=1&_issn=02728842&md5=34ed39e41f75ed0c199a5c6d58e8dd4f">mg class="imgLazyJSB inlineImage" height="15" width="44" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0272884216000031-si0002.gif">mathContainer hidden">mathCode"><math altimg="si0002.gif" overflow="scroll"><mrow><mi>Pmi><mi>mmi><mover accent="true"><mn>3mn><mo>&macr;mo>mover><mi>mmi>mrow>math> to the orthorhombic Pbnm occur in the temperature regions of 680–730 °C and 300–680 °C,respectively. The phase transformations of the tetragonal P4mm to the cubic mmlsi0002" class="mathmlsrc">mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0272884216000031&_mathId=si0002.gif&_user=111111111&_pii=S0272884216000031&_rdoc=1&_issn=02728842&md5=34ed39e41f75ed0c199a5c6d58e8dd4f">mg class="imgLazyJSB inlineImage" height="15" width="44" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0272884216000031-si0002.gif">mathContainer hidden">mathCode"><math altimg="si0002.gif" overflow="scroll"><mrow><mi>Pmi><mi>mmi><mover accent="true"><mn>3mn><mo>&macr;mo>mover><mi>mmi>mrow>math> occurs in the temperature region of 200–230 °C, whereas the phase structure of orthorhombic Pbnm keeps unchanged below 850 °C. Based on careful characterization of crystal structure and phase transition as a function of temperature, the phase diagram of the pseudo-binary BiFeO<sub>3sub>–LaFeO<sub>3sub> system has been constructed. The phase diagram manifests that the Bi<sub>1&minus;m>xm>sub>Lam><sub>xsub>m>FeO<sub>3sub> (0≤m>xm>≤1.00) solid solution provides more options to tune the magnetism and multiferroism, as the crystal structures with polarity feature occur in a wide doping concentration of La (m>xm>≤0.30). We then selectively studied the magnetic properties of possible multiferroic phases, i.e. R3c and P4mm phases. The results revealed that both the magnetic remanence and the coercive field of Bi<sub>1&minus;m>xm>sub>Lam><sub>xsub>m>FeO<sub>3sub> (0<m>xm>≤0.30) increased with the La content.