Bi₅Ti₃FeO₁₅ (pentabismuth trititanium iron pentadecaoxide), which is a multiferroic four‐layer Aurivillius phase compound, has received much attention in recent years. However, three mutually inconsistent orthorhombic space groups, i.e. A2₁am, Fmm2 and Pnn2, have been reported for the room‐temperature phase of Bi₅Ti₃FeO₁₅ by X‐ray and neutron diffraction investigations. Here, electron diffraction results are presented and discussed for the first time to unambiguously clarify the room‐temperature space group of ceramic Bi₅Ti₃FeO₁₅. It has been found that all the observed reflections from the ceramic agree with those expected in A2₁am, while the observed reflections 011, 013 and 015 should be forbidden in the case of Fmm2, and no 107 and 109 reflections were observed although allowed for Pnn2. The present study has demonstrated that the space group of Bi₅Ti₃FeO₁₅ ceramic is A2₁am rather than Fmm2 or Pnn2, an identification that proved to be a challenge for X‐ray diffraction. On the basis of the space group A2₁am, the lattice parameters of the Bi₅Ti₃FeO₁₅ ceramic were calculated from its X‐ray diffraction data.

中文翻译：

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Bi5Ti3FeO15多铁陶瓷空间群的电子衍射研究。

近年来，Bi ₅ Ti ₃ FeO ₁₅（五钛酸_三铋钛铁）是一种多铁性的四层Aurivillius相化合物。然而，三个相互不一致正交空间基团，即A 2 ₁上午，FMM 2和PNN 2，已经报道了Bi的室温相₅的Ti ₃的FeO ₁₅通过X射线和中子衍射调查。在这里，首次给出并讨论了电子衍射结果，以明确阐明陶瓷Bi ₅ Ti ₃的室温空间群氧化铁₁₅。已经发现，从陶瓷观察到的所有反射都与在A 2 ₁ am预期的反射一致，而在Fmm 2的情况下应禁止观察到的反射011、013和015，尽管观察到107和109的反射，但是允许PNN 2.本研究表明，Bi的空间群₅的Ti ₃的FeO ₁₅陶瓷是阿2 ₁是而不是FMM 2或PNN 2，被证明是用于X射线衍射中的挑战的标识。在空间群A的基础上2 ₁上午，则Bi的晶格参数₅的Ti ₃的FeO ₁₅陶瓷是从它的X射线衍射数据来计算。