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The purpose of this study was to investigate the correlation between amorphous content and the characteristics of micrometer-sized photocatalyst particles. As a model of photocatalyst, tungsten trioxide (WO3) particles with controllable amorphous contents were used. To comprehend the amorphous content parameter precisely, the experiments were conducted by heating amorphous WO3 powders at a specific temperature without additional chemicals or solvents. Thus, the percentage of amorphous in the WO3 particles was controlled independently in the constant particle outer sizes and morphology. Micrometer-sized catalyst was used to avoid the misleading photocatalytic measurements due to the over-dominancy of other catalytic parameters (such as excessive surface area and quantum confinement effect). The results revealed that in the constant process condition, the photocatalytic properties were strongly dependent on the amorphous content in the catalyst. Decreases in this parameter had a strong influence to the enhancement of the photodecomposition rate of organic material. The tendency for the influence of amorphous content was also confirmed by varying the number of catalysts in the photocatalytic process. The study was also completed with the theoretical consideration for the phenomenon happening during the WO3 crystallization (transformation of amorphous into hexagonal and monoclinic crystal structure) and the photocatalytic process. Keywords: Amorphous, Crystallite size, Tungstate material, Curcumin, Photodecomposition rate

The correlation between crystallite size and the characteristics of micrometer-sized photocatalyst particles was investigated. As a model of photocatalyst, monoclinic tungsten trioxide particles with controllable crystallite sizes were used. The crystallite size was controlled independently in the constant particle outer diameters to comprehend the crystallite size parameters precisely. To minimize the misleading photocatalytic measurements due to the over-dominancy of other catalytic parameters (such as excessive surface area and quantum confinement effect), the present study utilized micrometer-sized particles. The results revealed that in the constant process condition, the photocatalytic properties were strongly dependent on the material crystallinity. Increases in the crystallite sizes had a strong influence to the enhancement of the photodecomposition rate of organic material. The tendency for the impact of crystallite size was also confirmed by varying the number of catalysts in the photocatalytic process. To confirm the analysis of photocatalysis, the study was completed with the theoretical consideration and the proposal of the particle formation as well as the phenomena that happen during the photocatalytic process. Keywords: Amorphous, Crystallite size, Tungstate material, Curcumin, Photodecomposition rate