The Rietveld refinement technique has been used to determine the extent of intergrowth of the Bi₂Sr₂CuO_6+x phase and co-crystallization of competing phases in the high-temperature superconductor Bi₂Sr₂CaCu₂O_8+x (Bi-2212). The refinement was done on powder diffractograms obtained on powders made by grinding single crystals of Bi₂Sr₂CaCu₂O_8+x grown using two different self-flux techniques, namely the pressure technique and the regrowth technique, and ground for either 2 min or 2 h. The Rietveld programs JANA and FULLPROF were used for the refinement and both gave consistent results. The Bi and Sr atom positions were refined in the average structure of centrosymmetric space group Bbmb. To incorporate Bi-atom modulation and extract information about the modulation vector, refinement was done in the centrosymmetric space group (Bbmb(0γ1)). The b* component of the modulation vector decreases with a decrease in the superconducting transition temperature in the pressure-technique sample compared with the regrowth sample, suggesting a better alignment of the CuO₂ planes with respect to the Bi–O planes in the pressure-technique sample. All the samples exhibit a strong preferred orientation effect. Values of the March–Dollase parameters corresponding to the preferred orientation function were obtained. Brindley absorption contrast factors t_ϕ were also calculated, together with the effect of microabsorption on the number of phases present in each sample. Rietveld refinements incorporating all the factors resulted in excellent values for the goodness-of-fit parameters for all the samples, with the lowest value of 2.08 for the pressure-technique sample ground for 2 min. Additionally, the powders corresponding to the pressure-technique crystals have no co-crystallizing phase and ∼94% of the Bi-2212 phase, suggesting that crystals grown by the pressure technique are of extremely good quality, much better than those grown by the regrowth flux technique.

中文翻译：

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通过 Rietveld 细化研究对 Bi2Sr2CaCu2O8+x 和相互竞争的共生相和共结晶相进行定量相分析

所述Rietveld修正技术已被用来确定双向的共生的程度₂的Sr ₂ CuO的_{6+ X}相，并在高温竞争阶段的共结晶超导体的Bi ₂的Sr ₂ CaCu ₂ ö _{8+ X}（双2212)。对通过研磨使用两种不同的自熔技术（即压力技术和再生长技术）生长的 Bi ₂ Sr ₂ CaCu ₂ O _{8+ x}单晶制成的粉末获得的粉末衍射图进行精修，并研磨 2 分钟或 2 小时。里特维尔德计划JANA和FULLPROF用于细化，两者都给出了一致的结果。Bi和Sr原子位置在中心对称空间群Bbmb的平均结构中被细化。为了结合双原子调制并提取有关调制向量的信息，在中心对称空间群( Bbmb (0γ1)) 中进行了细化。与再生长样品相比，调制矢量的b * 分量随着压力技术样品中超导转变温度的降低而降低，表明 CuO _{2 的}排列更好相对于压力技术样品中的 Bi-O 平面的平面。所有样品都表现出强烈的择优取向效应。获得了与首选方向函数相对应的 March-Dollase 参数值。布林德利吸收对比因子t _ϕ还计算了微吸收对每个样品中存在的相数的影响。结合所有因素的 Rietveld 改进导致所有样品的拟合优度参数都具有出色的值，其中压力技术样品研磨 2 分钟的最低值为 2.08。此外，压力技术晶体对应的粉末没有共结晶相，约 94% 为 Bi-2212 相，这表明压力技术生长的晶体质量非常好，远好于再生长的晶体。通量技术。