Kainzbauer Peter, Richter Klaus W, Ipser Herbert
University of Vienna, Faculty of Chemistry, Department of Inorganic Chemistry - Functional Materials, Althanstrasse 14, 1090 Vienna, Austria.
J Phase Equilibria Diffus. 2018;39(1):17-34. doi: 10.1007/s11669-017-0600-5. Epub 2017 Oct 13.
The binary bismuth-rhodium (Bi-Rh) phase diagram was reinvestigated from 23 to 60 at.% Rh with focus on the BiRh phase, applying powder-x-ray diffraction (XRD), high temperature powder-XRD, differential thermal analyses and scanning electron microscopy. The phase boundaries of the BiRh phase at 750 °C and the temperature of its peritectic decomposition were refined. In addition, the existence of the two phases BiRh and BiRh (in two modifications depending on temperature) could be confirmed. Most of the reaction temperatures reported in the literature could be verified within a range of about ± 10 °C. Nevertheless, a few temperatures had to be revised, such as those of the peritectic reactions L + Rh BiRh at 979 °C and L + BiRh -BiRh at 785 °C. No evidence could be found for the presence of a stable BiRh phase in well annealed samples; from the present results it must be concluded that BiRh is actually metastable. On the other hand, a new orthorhombic phase BiRh was discovered which crystallizes in the MnP structure type (Pmna). It was found that the temperatures of the transition between the low-temperature modification -BiRh and its high-temperature form -BiRh depend considerably on the presence or absence of metastable BiRh and stable BiRh, respectively.
采用粉末X射线衍射（XRD）、高温粉末XRD、差热分析和扫描电子显微镜，对二元铋-铑（Bi-Rh）相图在铑含量为23%至60%（原子分数）范围内进行了重新研究，重点关注BiRh相。细化了BiRh相在750°C时的相界及其包晶分解温度。此外，证实了BiRh和BiRh（根据温度有两种变体）这两个相的存在。文献中报道的大多数反应温度在约±10°C的范围内得到了验证。然而，有几个温度必须修正，例如979°C时的包晶反应L + Rh → BiRh和785°C时的L + BiRh → BiRh。在充分退火的样品中未发现稳定的BiRh相存在的证据；根据目前的结果，必须得出BiRh实际上是亚稳相的结论。另一方面，发现了一种新的正交相BiRh，它以MnP结构类型（Pmna）结晶。发现低温变体BiRh和高温形式BiRh之间的转变温度分别很大程度上取决于亚稳相BiRh和稳定相BiRh的存在与否。
