STRUCTURE OF A FERROELECTRIC AND FERROELASTIC MONODOMAIN CRYSTAL OF THE PEROVSKITE BIFEO3
STRUCTURE OF A FERROELECTRIC AND FERROELASTIC MONODOMAIN CRYSTAL OF THE PEROVSKITE BIFEO3
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DOI：
10.1107/s0108768190006887
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发表时间：
1990-12-01
期刊：
影响因子：
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通讯作者：
SCHMID, H
中科院分区：
文献类型：
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作者：
KUBEL, F;SCHMID, H
报道了在294 K下BiFeO₃铁电和铁弹单畴单晶的X射线衍射数据。氧化铋铁，M(r)=312.83，R3c，λ-(Mo K -α)=0.7107埃，a(六方)=5.57874(16)，c(六方)=13.8688(3)埃，V(六方)=373.802(17)埃³，a(菱方)=5.6343埃，α(菱方)=59.348°，V(菱方)=124.601埃³，Z = 6，D(x)=8.337 Mg m⁻³，μ = 75.97 mm⁻¹，F(000)=798，对于422个独立反射，R = 2.4，wR = 1.9%。该结构可描述为菱面体畸变的简单立方钙钛矿晶胞。氧八面体发生畸变，O - O最小和最大距离分别为2.710(7)埃和3.015(9)埃，并且围绕三重轴旋转约±α = 13.8(3)°。铁原子沿着三重轴从变形氧八面体的中心偏移约0.134(7)埃。铋原子相对于两个相邻八面体中心沿着三重轴偏移约0.540(7)埃。Bi - Fe距离为3.0617(11)埃和3.8726(11)埃。氧原子从Bi₄平面偏移0.2877(6)埃。铁 - 氧链的角度为165.04(21)°(O - Fe - O)和154.1(4)°(Fe - O - Fe)，二面角为127.8(9)°(O - Fe - O - Fe)和121.6(9)°(Fe - O - Fe - O)。分析了铁电极化机制：计算了P(s)在60°、120°和180°翻转时的原子位移，发现铁的位移分别为0.44埃、0.62埃和0.82埃。对于α（-α）旋转的八面体，平均氧位移分别为0.87(0.89)埃、1.13(1.24)埃和1.34(1.53)埃。平均铋位移小于0.06埃。由于位移按照P(s)的60°、120°和180°翻转顺序增加，180°反转必定具有非常高的活化能，将会被避免。
X-ray diffraction data on a ferroelectric and ferroelastic monodomain single crystal of BiFeO3 at 294 K are reported. Bismuth iron oxide, M(r) = 312.83, R3c, lambda-(Mo K-alpha) = 0.7107-angstrom, a(hex) = 5.57874 (16), c(hex) = 13.8688 (3)-angstrom, V(hex) = 373.802 (17) angstrom-3, a(rh) = 5.6343-angstrom, alpha-rh = 59.348-degrees, V(rh) = 124.601-angstrom-3, Z = 6, D(x) = 8.337 Mg m-3, mu = 75.97 mm-1, F(000) = 798, R = 2.4, wR = 1.9% for 422 independent reflections. The structure can be described as a rhombohedrally distorted simple cubic perovskite cell. The oxygen octahedron is distorted with minimum and maximum O-O distances of 2.710 (7) and 3.015 (9)-angstrom, respectively, and rotated by about +/-alpha = 13.8 (3)-degrees around the threefold axis. The iron atom is shifted away from the centre of the deformed oxygen octahedron by about 0.134 (7)-angstrom along the threefold axis. The bismuth atom is shifted with respect to two neighbouring octahedron centres by about 0.540 (7)-angstrom along the threefold axis. Bi-Fe distances are 3.0617 (11) and 3.8726 (11)-angstrom. The oxygen atom is displaced by 0.2877 (6)-angstrom away from the Bi4 plane. The iron-oxygen chain has angles of 165.04 (21) (O-Fe-O) and 154.1 (4)-degrees (Fe-O-Fe), and dihedral angles of 127.8 (9) (O-Fe-O-Fe) and 121.6 (9)-degrees (Fe-O-Fe-O). The ferroelectric poling mechanism was analyzed: atom displacements were calculated for 60, 120 and 180-degrees switching of P(s) and found to be 0.44, 0.62 and 0.82-angstrom for iron. Average oxygen displacements for +alpha (-alpha) rotated octahedra were 0.87 (0.89), 1.13 (1.24) and 1.34 (1.53)-angstrom. Average bismuth shifts were less than 0.06-angstrom. As the displacements increase in the order 60, 120 and 180-degrees switching of P(s), the 180-degrees reversal must have a very high activation energy and will be avoided.