Synthesis of blue-luminescent CaNb<sub>2</sub>O<sub>6</sub> by using a biphasic liquid method at low temperatures

Abstract

We investigated a novel simple method to synthesize CaNb2O6 from precursors formed in immiscible liquid–liquid biphasic systems. Niobium pentaethoxide and calcium acetate monohydrate were used as starting materials, which were dissolved separately in hexane and water, respectively. After putting the hexane solution on the aqueous solution, they started to react at the interface of the two liquid phases and then a mixture of calcium acetate and amorphous niobate gels was precipitated in the aqueous solution at room temperature. The precipitates could be transformed to CaNb2O6 by heating at 700°C for 30 min. The morphology of the CaNb2O6 sample was characterized as rough and dimpled spheres 400–500 nm in size. The sample exhibited a blue emission upon excitation with ultraviolet light. A comparative study using a one-phase liquid method or a solid-state reaction method has strongly suggested that the biphasic liquid method is advantageous for obtaining highly luminescent CaNb2O6 at the lower processing temperatures.