Ti-doped and undoped CaFe 2 O 4 powders were prepared from a malic acid complex and their properties were evaluated using analytical instruments. According to an XRD measurement, there were no traces of impurity phases in 5 mol % Ti-doped CaFe 2 O 4 powder, while impurity phases such as ¡-Fe 2 O 3 and CaTiO 3 were observed for 10 mol % Ti-doped CaFe 2 [Received September 16, 2013; Accepted December 3, 2013] For several decades, the physical and chemical properties of calcium ferrite (CaFe 2 O 4 ) crystal have been researched widely because of its useful applications such as in gas absorbers, in electrochemical devices for high-temperature use, and as an oxidation catalyst.1)3) CaFe 2 O 4 has recently attracted considerable attention as a new photocatalyst material owing to its excellent photoreductive property for H 2 O and CO 2 . 4)9) In general, CaFe 2 O 4 is prepared by a solid-state reaction. Although a solidstate reaction is most frequently used because of ease and convenience, it has several problems such as changes in stoichiometric ratio and the ease of formation of impurity phases.10) This is because the starting materials must be repeatedly ground and calcined many times to prepare the intended crystal phase. As a result, the specific surface area of the product decreases and the catalytic activity has inevitably falls. Needless to say, a high surface area is an important property of surface functionality materials such as catalysts.Marcilly and co-workers have reported a new preparation method employing organic acids (citric, malic, tartaric, glycolic acids etc.) to obtain metal oxides. 11) They showed that H + in an organic acid with -OH or -COOH groups is replaced by the metal ion in the solution and the organic acid complex is easily formed. This complex is available for a precursor to prepare the objective material. Therefore, it is expected that the precursor is transformed to objective oxide at lower calcination temperature than the case of a solid-state reaction method and the resulting final product has a large surface-area and a high homogeneity.In the present study, we have examined the preparation of CaFe 2 O 4 powder with high specific surface area from a malic acid complex, instead of employing a solid-state reaction, and characterized the powder by X-ray diffractometry (XRD), X-ray photoelectron spectrometry (XPS), fluorescence X-ray spectrometry (XRF), scanning electron microscopy (SEM), surface area measurement, and UVvis spectrometry. Furthermore, the effect of Ti addition on the crystal phase, microstructure, specific surface area, and optical properties of CaFe 2 O 4 was investigated.CaFe 2 O 4 powder was synthesized by a malic acid complex method. Ca(NO 3 ) 2 ·4H 2 O, Fe(NO 3 ) 3 ·9H 2 O, and malic acid in a 1:2:3 molar ratio were dissolved in deionized water. The addition of Ti to CaFe 2 O 4 carried out using Ti[OCH(CH 3 ) 2 ] 4 . The amount of Ti doped set to 5 and 10 mol % to Fe. The solution was dehydrated and heated on a hot plate to prepare the precursor powder of CaFe 2...
