Synthesis of the Bi ₂ GeO ₅ Ferroelectric Crystalline Phase from a Nonstoichiometric Batch

In the present research, an individual Bi2GeO5 crystalline phase is successfully synthesized on air from Bi2O3-Bi-GeO2 batch in which some part of bismuth oxide is replaced by metallic bismuth to create an oxygen deficiency. The crystallization process is carried out by three methods: heterophase synthesis, melt cooling, and glass crystallization. The structure of the formed crystalline phases as well as the influence of the bismuth metal quantity and synthesis temperature on crystallization results have been investigated by X-ray diffraction (XRD). It is found that both the melt temperature rising, and an increase of metallic bismuth amount led to the formation of an individual Bi2GeO5 phase. The optimal initial batch compositions and crystallization conditions to produce an individual Bi2GeO5 or Bi4Ge3O12 phase have also been found.