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$\ce{ZrO2}$ has great properties, biocompatibility, chemical resistance, decent scratch resistance, great thermal resistance and refraction, but it could be better. It, like glass, will slowly react with $\ce{HF}$ and other fluorine substances, specifically oxidizing agents with fluorine.

Normally to make stuff resistant to fluorine the only thing to do is react it with fluorine in such a way that the reacted surface stays where it is. Steel flasks, for example, can be polished in a low oxygen environment and treated with fluorine to make the surface of the steel an iron fluoride.

Unlike iron oxides, fluorine won’t react with it because fluorine is a more effective oxidizing agent and essentially nothing else can break apart the intramolecular bonds keeping the iron fluoride together under normal conditions. It’s like, you can’t burn something twice, you can’t fluorinate something twice. That might not work with $\ce{ZrO2}$, I was going to say cause it doesn’t burn or oxidize but it’s already an oxide so that’s a bad reason.

Anyways PTFE doesn’t react with fluorine cause it’s just fluorine and carbon already.

So here’s my question: Can you do that with $\ce{ZrO2}$? Would Zirconium form a stable molecule with fluorine? If so, would it have similar properties, or at least be solid at STP? If not, is there another way of making $\ce{ZrO2}$ fluorine resistant? Or something else like $\ce{ZrO2}$ that’s more fluorine resistant?

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  • $\begingroup$ Zirconium fluoride ZrF4 is the equivalent of ZrO2 with fluorine, see en.wikipedia.org/wiki/Zirconium_tetrafluoride . $\endgroup$
    – PLD
    Commented May 28, 2020 at 16:42
  • $\begingroup$ Zirconium tetrafluoride melts at 910 c compared to ZrO2’s 2715 c. It’s used in really expensive and underwhelming optical equipment, and some nuclear reactors. It’s soluble in water, less dense than ZrO2, and much more reactive. I’m trying to figure out if you can HF-proof ZrO2, not make a fairly reactive precursor to more interesting chemicals or make overhyped lenses. $\endgroup$
    – Delaney Fitzpatrick
    Commented May 29, 2020 at 19:48
  • $\begingroup$ Sorry if that sounded mean, it was meant to be funny and interesting and provoke further discussion and I couldn’t figure out how to do that well. $\endgroup$
    – Delaney Fitzpatrick
    Commented May 29, 2020 at 19:50

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One way might be adding another metal oxide so such that the corresponding metal fluoride is insoluble in water or hydrofluoric acid. This most likely is to be in the form of a coating on the zirconia. Lanthanide oxides are a possibility as they have both higher melting points and their corresponding fluorides are insoluble in water. Also, yttrium and cerium(III) oxides are already used as stabilizers for zirconia. Adding enough of these oxides may decrease the solubility in HF. In fact, one reason why CaO present in soda-lime glasses is to reduce the solubility of the sodium oxide in aqueous solution. This article does state the possibility of a protecting layer when zirconia doped yttria (more yttria than zirconia) is exposed to fluorine radicals: https://www.sciencedirect.com/science/article/abs/pii/S0272884220334015

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