选用四种溶液与不同含量的氮化硅粉体混合得到不同的悬浊液, 在石英坩埚内壁制备了氮化硅涂层, 并将其用于冶金法提纯多晶硅; 用扫描电镜、电子探针等分析了多晶硅铸锭与坩埚内壁的粘连面积、铸锭表面微裂纹形貌和反应层厚度, 得到与最佳多晶硅铸锭脱模相对应的制备涂层的工艺参数, 同时分析了熔炼过程中氮化硅涂层与硅熔体间的反应机制。结果表明: 将含质量分数为8%聚乙烯吡咯烷酮的乙醇溶液和质量分数为60%氮化硅的悬浊液喷涂到坩埚内壁上, 并经210 ℃×15 min烧结后的氮化硅涂层不易分解, 坩埚内壁保持完整, 铸锭的脱模效果最好; 随熔炼温度升高氮化硅涂层分解加剧, 在涂层与硅铸锭的接触面处形成了由大颗粒氮化硅组成的连续层, 减小了坩埚和涂层中杂质向硅铸锭内部扩散的可能性。

Various suspensions were made by four kinds of solutions mixing with different Si3N4 powders contents; the Si3N4 coatings, which used for polycrystalline silicon purification, were prepared in quartz crucibles inwall; the adhesive area between polycrystalline silicon ingots and crucible, microcrack morphology on the ingots surface and thickness of reaction layers were analyzed by SEM, EPMA, and so on. The process parameters prepared coating matching with best polycrystalline silicon knockout were got and the reaction mechanism between Si3N4 coating and melt silicon in melting process was analyzed. The results show that the coating was prepared by spraying the suspensions including the ethyalcohd solution containing 8wt% PVP, 60wt% SiC on crucibles inwall, and the coating sintered at 210 ℃ for 15 min was not decompounded, the crucible inwall was integrated, and the knockout effect of the ingot was best. The dissolution of Si3N4 coating aggravated with the increase of smelting temperature. The continuous layer, which reduced the possibility of impurity diffusing from crucible and coating to silicon ingot interior, was consisted of large Si3N4 particles on the interface of coating and silicon ingot.