Preparation method of thorium tetrafluoride material for infrared coating

The invention discloses a preparation method of a thorium tetrafluoride material for infrared coating, and relates to the technical field of infrared coating, and the preparation method comprises the following steps: A, concentrating a thorium nitrate solution (100-150g of ThO2); b, adding HNO3 to adjust the acidity; and C, thorium nitrate purification process. According to the method, impurities such as silicon and zirconium in thorium are deeply removed through a chemical method, a complexing precipitator with high selectivity is adopted, impurities such as silicon and zirconium which are difficult to remove are deeply removed through multi-stage controlled washing, the flow of the preparation process is shortened, and the effects of high impurity removal rate, low cost, cleanness and high efficiency are achieved; metal impurities in a nitric acid system are eluted by adopting special combined resin in combination with multi-acidity gradient, the deep removal effect of the impurities is improved, thorium ni