ИСТИНА

The ferroelectric crystalline phase Bi2GeO5 has spontaneous polarization value comparable to BaTiO3 ceramics. To date, most researchers consider this phase to be metastable so it can be hardly synthesized by conventional crystal growth methods. We offer a new look at the phase formation in the Bi-Ge-O system, which considers Bi2GeO5 as an oxygen-deficient phase and makes it easy to synthesize from non-stoichiometric compositions. The Bi2GeO5 single phase has been successfully synthesized from Bi2O3-Bi-GeO2 batch when Bi oxide has been partially replaced by metallic Bi to form an oxygen deficiency. The crystallization was made both in solid phase and from melts at different temperatures. The structure of the formed crystal phases have been investigated by XRD. It was found that both the melt temperature rise and metallic Bi amount increase led to the formation of Bi2GeO5 single phase. The optimal initial batch compositions and crystallization conditions to produce a single Bi2GeO5 crystal phase has also been found. The research was supported by the Ministry of Science and High Education of the Russian Federation by the project FSSM-2020-0003.