Abstract Bi2Sr2-xRbxCo2O8+δ materials with 0 ≤ x ≤ 0.125 were fabricated via the classical solid-state route, and textured using the laser floating zone method. As-grown materials were composed of different secondary phases due to the incongruent melting of this compound. These secondary phases were drastically reduced through an annealing procedure, consisting in heating at 800 °C for 12 h. XRD has not detected any secondary phase on the annealed samples, due to the overlapping of thermoelectric and main secondary phase diffraction peaks. SEM observations have confirmed this microstructural evolution, and shown that Rb-substitution further decreases the secondary phases content and enhances grain orientation. These microstructural features, together with the possible increment of charge carrier concentration due to Rb-doping, decreased electrical resistivity, while Seebeck coefficient has only been slightly reduced. Consequently, the Rb doped samples reached higher power factor (PF) values than the pure ones. The biggest PF values at room temperature (0.11 mW/K2m) are higher than the reported for single crystals (0.07 mW/K2m), while at 650 °C (0.20 mW/K2m), they are also higher than the obtained in textured samples and measured along the conducting plane (0.14 mW/K2m).

中文翻译：

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退火诱导 Bi2Sr2-xRbxCo2O8+δ 激光生长陶瓷电性能的提高

摘要 0 ≤ x ≤ 0.125 的 Bi2Sr2-xRbxCo2O8+δ 材料采用经典固态途径制备，并采用激光浮区法进行织构。由于该化合物的不一致熔化，生长时的材料由不同的第二相组成。这些第二相通过退火程序大大减少，包括在 800 °C 下加热 12 小时。由于热电和主要次生相衍射峰的重叠，XRD 在退火样品上没有检测到任何次生相。SEM 观察证实了这种微观结构演变，并表明 Rb 取代进一步降低了第二相含量并增强了晶粒取向。这些微观结构特征，以及由于 Rb 掺杂可能增加的电荷载流子浓度，电阻率降低，而塞贝克系数仅略有降低。因此，Rb 掺杂的样品达到了比纯样品更高的功率因数 (PF) 值。室温下的最大 PF 值 (0.11 mW/K2m) 高于报道的单晶 (0.07 mW/K2m)，而在 650 °C (0.20 mW/K2m) 下，它们也高于纹理样品中获得的值并沿导电平面测量 (0.14 mW/K2m)。