Study on fluorine vacancy defects in yttrium fluoride coating materials

Abstract

Abstract Rare-earth fluoride coating materials have attracted wide attention as a substitute for ThF4 low-refractive index materials. However, the coating materials and coated films fail to achieve the desired results due to vacancy defects caused by their fluorine-loss decomposition characteristics. To explore the rare earth fluoride coating materials’ fluorine loss influence law, the melt crystallization method is used to simulate the yttrium fluoride (YF3) pre-melting process through the electronic paramagnetic resonance (EPR) obtained at different temperatures under the fluorine vacancy defects change rule. According to the number of unpaired spintrons, the number of spintrons in each vacancy is calculated. The results show that the fluorine vacancy defects increase with the increase of temperature, the formation of YF3 fluorine vacancy defects does not affect the change of crystal structure, and the addition of the additive ammonium hydrogen fluoride (NH4HF2) can reduce the oxygen content of YF3 and effectively inhibit the formation of fluorine vacancy. The effect is gradually obvious with the amount of additives added.