Patent ID: 11566328

Abstract:
Aqueous solutions of halogenides (oxyhalides) of zirconium and hafnium (M) with values of α=X/M near one, for X=Cl, Br and I form amorphous solids or glasses, designated as M,X, in contrast to important crystalline oxyhalide end members with α=2 (designated as MOX). The present disclosure describes methods for producing amorphous thin films comprising halogenides upon evaporation, and provides some measured physical properties, with attention to compositions for α<2. The value of a below which only glasses are formed is about one for oxychlorides and oxybromides of both Zr and Hf. The chemical formulas for all the halogenide thin films prepared as noted above can be written as a function of the single parameter α, according to M(OH)4-αXα.(4α-1)H2O. This is valid for e.g., crystalline zirconium oxychloride octahydrate, and for the glassy solids found for α<2 and down to the onset of hydrolysis, α≈0.5. Thin films made by the disclosed methods are highly dense (90% of theoretical crystal density), extremely smooth (rms<0.4 nm), and highly transparent in the visible spectrum, >90%. Such thin films are useful as alkali diffusion barriers.