Is there a selective wet etch of Bi2O3 Bismuth Oxide?

I'm looking for a wet etch of Bismuth Oxide that **does not etch $\ce{Bi}$ itself.**


There are obviously chemicals that etch $\ce{Bi2O3}$, but $\ce{Bi}$ is pretty fragile, so almost everything I've found that can etch $\ce{Bi2O3}$ also etches Bi, and usually more rapidly than the $\ce{Bi2O3}$ itself.


However, someone recently mentioned to me in passing that there was a chemical that could do this, but they didn't remember what it was.


Searching Google, I found [this,](https://books.google.com/books?id=ZDyTr9uJnAsC&pg=PA590&lpg=PA590&dq=bismuth%20oxide%20selective%20etch&source=bl&ots=MdAp64Wx1E&sig=qe99pBGk4uHb983fq8oYfNNBqQM&hl=en&sa=X&ved=0CCQQ6AEwAGoVChMItvbGv9DHxgIVgRaSCh3q0QT6#v=onepage&q=bismuth%20oxide%20selective%20etch&f=false) but that's RIE -- not wet etching.


I've also read about people using $\ce{H2}$ gas to reduce the oxide back to $\ce{Bi}$, but again, not wet etching.


Does anyone have any idea? I know it's a specific and uncommon question.


