Layered (Cu,Fe) Oxides of Double Perovskite Structure.II.Extension of Solid Solubility of Copper in (Ba,La)Y(Cu_(0.5+x)Fe_(0.5-x))_(2)O_(5+y) via High-Pressure Heat Treatment
Layered (Cu,Fe) Oxides of Double Perovskite Structure.II.Extension of Solid Solubility of Copper in (Ba,La)Y(Cu_(0.5+x)Fe_(0.5-x))_(2)O_(5+y) via High-Pressure Heat Treatment
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双钙钛矿结构的层状(Cu,Fe)氧化物.II.铜在(Ba,La)Y(Cu_(0.5 x)Fe_(0.5-x))_(2)O_(5 y)中固溶度的扩展
DOI：
10.1103/physrevb.59.1377
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发表时间：
1999
影响因子：
3.7
通讯作者：
H. Yamauchi
中科院分区：
文献类型：
--
作者：
M. Nagase;J. Lindén;H. Suematsu;M. Karppinen;H. Yamauchi
本文成功地扩展了双钙钛矿结构(Ba，L a)Y(Cu，Fe)2O5+δ相中铜的固溶极限。含有杂质相的常压合成样品经5 Gpa和1200℃高压热处理后，(Ba1−2xLa2x)Y(Cu0.5+xFe0.5−x)2O5+δ体系。高压合成(Ba0.6La0.4)Y(Cu0.7Fe0.3)2 O5+δ材料的电子显微镜观察和X射线能谱分析表明，样品中铜和铁的比例变化很大，平均为Cu：Fe=0.70：0.30，共9个颗粒。由此可以得出结论：在氧金字塔中实现了铜大于铁的0112相。为了获得富铜的0112相，必须同时用三价镧取代二价钡位。根据57Fe穆斯堡尔谱数据，估算了五配位和六配位铁原子的相对强度，并估计了结构中过剩氧量的δ≈为0.23。此外，对x=0.2样品的穆斯堡尔和磁化率测量都表明，富铜材料的Néel温度低于化学计量比x=0的材料的相应转变温度。最后，讨论了铜固溶度成功扩展的条件，并与0112结构的容差因子有关。
In this paper, we report successful extension of the solid-solubility limit of copper at the transition element site in the (B a, L a) Y (C u, F e) 2 O 5+ δ phase of the double-perovskite “0112” structure. Upon the high-pressure heat treatment at 5 GPa and 1200 C of the ambient-pressure synthesized samples that contained impurity phases, essentially single-phase samples were obtained for x up to 0.2 in the (Ba 1− 2 x La 2 x) Y (Cu 0. 5+ x Fe 0.5− x) 2 O 5+ δ system. TEM observations and TEM energy dispersive x-ray analyses for the high-pressure synthesized (B a 0.6 La 0.4) Y (C u 0.7 Fe 0.3) 2 O 5+ δ material showed that the ratio of copper to iron varies in the sample with an average value of C u: F e= 0.70: 0.30, as measured for nine grains. It could thus be concluded that a 0112 phase in which the amount of copper is larger than that of iron in the oxygen pyramid was realized. In order to obtain the copper-rich 0112 phase, simultaneous substitution of the divalent barium site by trivalent lanthanum was found necessary. From 57 Fe Mössbauer spectroscopy data, the relative intensities of five-and six-coordinated iron atoms were evaluated and the amount of excess oxygen in the structure could be estimated at δ≈ 0.23. Furthermore, both Mössbauer and magnetic-susceptibility measurements of the x= 0.2 sample showed that the Néel temperature of the copper-rich material is lower than the corresponding transition temperature observed for the material with the stoichiometric x= 0 composition. Finally, conditions for the successful extension of the copper solubility are discussed and related to the tolerance factor of the 0112 structure.