Relationship between phase structure and melting characteristics of low cesium KF-CsF-AlF₃ aluminum flux

The melting curves of low cesium KF-CsF-AlF₃ flux samples prepared by wetting synthesis method were measured with differential scanning calorimetry (DSC),and the effect of the flux compositions on the melting characteristics was analyzed and summarized. The phase structure and morphology of typical flux samples were analyzed by X-ray diffraction (XRD),scanning electron microscope (SEM) and energy spectrum analysis (EDS),respectively. The results indicated that the wetting synthesized flux was mixture of rod-shaped K₂AlF₅ and flocculent Cs₂KAl₃F₁₂. Because the localized compositions deflected from the eutectic point E₄ or E₅,it was difficult for the ternary eutectic reaction to occur during the melting process. However,the decompose of K₂AlF₅ at 505℃ and melting of Cs₂KAl₃F₁₂ at 525℃ occurred,which led to the large difference between the melting temperature of flux samples prepared by wetting synthesis method and that from the theoretical ternary phase diagram,and especially the increase of the liquidus.