TY - JOUR
T1 - Modulation structure in Bi2(La1-xCa1+x)CuO6.5+δ and (Bi2-xPbx)LaCaCuO6.5+δ systems
AU - Zhiqiang, Mao
AU - Mingliang, Tian
AU - Shun, Tan
AU - Jian, Zuo
AU - Yang, Xu
AU - Yu, Wang
AU - Chunyi, Xu
AU - Yuheng, Zhang
PY - 1994
Y1 - 1994
N2 - The microstructure of Sr-free bismuth cuprates, i.e., Bi2(La1-xCa1+x)CuO6.5+δ and (Bi2-xPbx)LaCaCuO6.5+δ, was determined by means of x-ray diffraction and electron diffraction (ED). ED analysis revealed that the two types of Sr-free compounds possess a monoclinic superstructural modulation, which is similar to Bi2Sr2CuO6+δ. In the Bi2(La1-xCa1+x)CuO6.5+δ system, the modulation wavelength along the b and c axes increased markedly with the Ca substitution for La. At the same time this substitution facilitated the commensurate-to-incommensurate transition. For the (Bi2-xPbx)LaCaCuO6.5+δ system, a similar change in the modulation wave vector was also observed. The dependence of the modulation vector on chemical composition can be best interpreted by the crystal-misfit model. In addition, Raman scattering analysis of the Bi2(La1-xCa1+x)CuO6.5+δ system showed that the vibrational properties of the oxygen atoms in the Bi-O bonding also changed with the increase in the modulation wavelength, and this behavior can be regarded as a consequence of the structural relaxation caused by the enhancement of the degree of crystal fit.
AB - The microstructure of Sr-free bismuth cuprates, i.e., Bi2(La1-xCa1+x)CuO6.5+δ and (Bi2-xPbx)LaCaCuO6.5+δ, was determined by means of x-ray diffraction and electron diffraction (ED). ED analysis revealed that the two types of Sr-free compounds possess a monoclinic superstructural modulation, which is similar to Bi2Sr2CuO6+δ. In the Bi2(La1-xCa1+x)CuO6.5+δ system, the modulation wavelength along the b and c axes increased markedly with the Ca substitution for La. At the same time this substitution facilitated the commensurate-to-incommensurate transition. For the (Bi2-xPbx)LaCaCuO6.5+δ system, a similar change in the modulation wave vector was also observed. The dependence of the modulation vector on chemical composition can be best interpreted by the crystal-misfit model. In addition, Raman scattering analysis of the Bi2(La1-xCa1+x)CuO6.5+δ system showed that the vibrational properties of the oxygen atoms in the Bi-O bonding also changed with the increase in the modulation wavelength, and this behavior can be regarded as a consequence of the structural relaxation caused by the enhancement of the degree of crystal fit.
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U2 - 10.1103/PhysRevB.49.6265
DO - 10.1103/PhysRevB.49.6265
M3 - Article
AN - SCOPUS:24844475420
SN - 0163-1829
VL - 49
SP - 6265
EP - 6269
JO - Physical Review B
JF - Physical Review B
IS - 9
ER -