Crystallization Behavior Of Alkali Iron Phosphate Glasses

Alkaali iron phosphate glasses include lithium iron phosphate glasses, sodium ironphosphate glasses, potassium iron phosphate glasses and mixed alkali iron phosphate glasses.These materials have potential application in the fields of biology, laser, infrared, optical glass,nuclear waste solidification and sealing. Crystallization can cause devitrification of glasses.However, controlled crystallization can be used to prepare glass-ceramics with excellentperformance. The study on the crystallization behavior of alkali iron phosphate glasses willhelp us to get the noncrystalline glass materials and provide guidelines for the preparation ofcrystallized glasses which for example can be used as sealing materials and lithium ionbattery materials. In addition, phosphate glass generally has a poor chemical stability. Glasssamples have to be stored for some time before crystallizatioton. Therefore, it is necessary tostudy glass chemical stability.In the present work, Li₂O-Fe₂O₃-P₂O₅（LIP） and Na₂O-Fe₂O₃-P₂O₅（SFP） glasses wereprepared by melting-quened method. The structure, glass transition and crystallizationbehavior of the glasses were analyzed by FTIR, DTA and XRD. The chemicail durability anddensity of the glasses were measured. Studies show that the addition of B₂O₃results indecrease the chemical stability of LIP glasses （33.33Li₂O-33.33Fe₂O₃-33.33P₂O₅） and incrasetransition temperature. When the amount of B₂O₃is5mol%and10mol%, the LIP glasseshave two crystallization peaks, which are proved to be caused by surface and bulkcrystallization, respectively.TiO₂, Cr₂O₃and ZrO₂,as the nucleating agents, improve the chemical stability of LIPglasses. The transition temperature decreases firstly and then increases with the increase ofthe added amount of TiO₂. The glass transition temperatures increase with Cr₂O₃or ZrO₂.LIP glasses, containing TiO₂, Cr₂O₃or ZrO₂show surface crystallization with thecrystalline phase of LiFeP₂O7. When the amount of TiO₂is increased, the crystallization layerbecomes thinner, however, the content of crystallites increases. The surface crystallization ofthe LIP glasses is promoted by Cr₂O₃or ZrO₂as well as TiO₂/Cr₂O₃complex nucleatingagents.Ternary SFP glasses have improved the chemical stability and glass transition temperature with increasing Fe₂O₃. SFP glasses can be melted upon thermal treatment. TheSFP glasses have low tendency to crystallization. TiO₂or ZrO₂as nucleating agents do notpromote the crystallization of SFP glasses. Fluorine can significantly promote thecrystallization of SFP glasses.