【摘要】 本文研究了Bi₂Sr₂CaCu₂O₈单晶（Tc=85K）、Bi_2-xPb_xSr₂Ca₂Cu₃O_y单相（Tc=107K）和Bi（Pb）-Sr-Ca-Cu-O非晶体室温下20-720cm^-1的Raman光谱.通过谱图的比较,我们认为456—466、631—650cm^-1是高Tc氧化物的特征谱,它们与Cu-O链及Cu-O面上的强电子—声子耦合有关;掺Pb导致Bi（Pb）-O双层之间氧的分布改变,增强了Bi（Pb）-O双层之间的耦合,从而有助于提高超导转变温度Tc.更多还原

【Abstract】 Since the discovery of high-Tc superconductivity in Bi-Sr-Ca-Cu-O system, a great deal of efforts has been made to study the structure and electronic properties of superconducting phases. The di cussion on Raman spectra of high-Tc superconductor aims to clarify the feature of phone structure and to gain information on physical properties of material. Much research work has been done on Raman spectra of Bi-Sr-Ca-Cu-O systeem while a little on Pb-doped Bi-Sr-Ca-Cu-O system.This paper discusses the similarities and differences of Raman spectra from (2212) single crystal (Tc = 85K, sp1), Pb doped (2223) phase (7% = 107K, sp2) and Pb-doped Bi-Sr-Ca-Cu-O nonsuperconductor which is amorphous solid (sp3). The spectra involve in 20-720cm-1. Raman spectra were excited by an argon laser (λ = 514.5nm) and detected by Model SPEX-140 Raman Spectrometer with a resolution of 4cm-1. All the experiments were carried out at room temperature.The lines of 169, 456-466 and 631-650cm-1 only occur in the spectra of sp1 and sp2. The spectrum of sp3 is quite different from those of sp1 and sp2 either in the location of lines or the structure of spectrum, which suggests the structure disparity. The most unambiguous character is that high intensity lines are always narrow, and they pile up on two broad weak backgrounds.The spectral feature of sp1 and sp2 is basically alike due to the structural similarity of (2212) and (2223) phase. By adding a Cu-O plane and a Ca plane, the (2212) phase turns into (2223) phase. Every corresponding plane has the same nearest neighbor environment of atoms. And for some plane even the second to the fourth nearest neighbors are the same (e.g. Sr-O plane). Only the nearest neighbor of the additional Cu-O plane and Ca plane is different. The main determination of short range force to mode frequency makes the spectra similar. Nevertheless, the obvious diversity is probably caused by some of the following reasons, loss of center symmetrical position of Ca, disparity in the neighbor environment of additional Cu-O plane and Ca plane, and Pb doped in sp2.Comparing the spectrum of sp2 with that of sp1, the function of dopand Pb is concluded. The substitution of Pb2+ for Bi3+ slightly enlarges the crystal constant, which is showed by the decrease of Bi-O mode (60cm-1 in sp1 and 52cm-1 in sp2). The substitution alters the oxygen distribution in doubled Bi(Pb)-O plane unit cell. We think the oxygen distribution is one of the important factors which affect superconductivity. In addition,630-650cm-1 line occurs both in the spectrum of sp1 and sp 2. So far from the available spectra of Bi oxide system and Y oxide system, we find that the common line at 620-650cm-1 is obvious.The structure similarity of Y-system and Bi system is that they both belong to perovskite structure. This line is therefore likely to represent the oscillation of a basic structure feature of perovskite-like structural elements, i.e. the motions associated with Cu-O plane and Cu-O chain.Contrasting sp3 to sp1 and sp2, the vibration modes of Sr and Cu along z axis decrease or even vanish while the modes concerned with vibration inside the plane still exist. According to this fact, the structural character of high-Tc superconductors is supposed to be four kinds of plane (i.e. Ca-O, Cu-O, Bi-O, Sr-O) piled up along z axis with somewhat partial substitution and translation between planes and vacancy of atoms etc. Spectrum of sp3 provides the evidence for this assumption.更多还原