pH-driven hydrothermal synthesis and formation mechanism of all BiPO4 polymorphs

• DOI: 10.1039/c2ce25337b
• Publication Date: 2012-08-17T14:33:11Z
• Authors: Yunjian Wang; Xiangfeng Guan; Liping Li; Guangshe Li
• Keywords: Monoclinic crystal system; Hydrothermal Synthesis

Understanding of formation mechanism inorganic solids by solution chemistry is always disturbed the interference effect impurities from starting materials. Herein, we exploited a new two-step route to selective synthesis BiPO4 different polymorphs with an aim eliminate impurity effect. The first step room-temperature hexagonal phase (HP), and second involves sufficient washing HP subsequent hydrothermal treatment under given conditions. nanocrystals was studied monitoring reaction parameters like pH, temperature, time, ions as well sample characterizations using X-ray diffraction (XRD) scanning electron microscope (SEM) techniques. It found that pH determinant parameter for polymorphs. Namely, at 240 °C strong acidic conditions (pH < 1), underwent transformation low-temperature monoclinic (LTMP), while neutral or weakly (3 7), transferred high-temperature (HTMP). Further increasing value up 14 led P-doped Bi2O3, which never accessible conventional but firing in air T > 750 °C. Based on these observations, two kinds transition mechanisms were discussed.