Purification and separation of other impurities from chloride raw materials, introduction of carbon dioxide to form carbonates, and reaction with high-purity fluoride in special equipment to generate fluoride salts. The reaction products are washed with hot pure water, and dried and dehydrated in a vacuum furnace. Adjust the temperature to remove free fluorine. Injecting hydrogen gas to transform the crystal phase changes the refractive index. Purify and separate other impurities from chloride raw materials, control the concentration and temperature, and add fluoride salt to react and precipitate to generate fluoride salt slurry. Wash with hot pure water to remove anions. Vacuum furnace dehydration. Remove free fluorine. Injecting hydrogen gas to transform the crystal phase changes the refractive index.