From smooth to stepped,coarse and derivative high index facets on (111) facets of cubic bismuth phosphate crystal

The bcc like structure of cubic bismuth phosphate (Bi_13.1PO_δ) crystal, makes (111) facets hardly be exposed according to the Bravais rule. In this paper, we are focusing on the exposure of smooth (111) facets on cubic bismuth phosphate crystal, and particularly on the process of the smooth (111) facets transforming to stepped and coarse (111) facets by varying the growth conditions, such as the Bi: P ratio of the raw materials, pH values, EDTA concentrations, etc. The results revealed that lower Bi: P ratio was beneficial to smooth (111) facets and with a rise of Bi: P ratio, the (111) facets transformed from smooth surface to stepped and coarse surfaces. With a moderate Bi: P ratio and EDTA concentrations, novel facets with high index were derived on the (111) facets, which were deduced as (611) facets. Additionally, the growth mechanism of the process was summarized in terms of the growth units affected by the Bi: P ratio, pH values and the presence of EDTA.