Hi David,

I am currently trying to etch Al2O3-ceramic substrates with phosphoric
acid. I did not try it with Titanium actually. There is an article of
Kirt R. Williams
"Etch Rates for Micromachining Processing—Part II" you can try to
find the answer in it.
Another way is to try dry etching such as RIE. There is a book
intiteled Etching in Microsystem Technology, author M. Köhler. Zou
will find the recepies in it.
Take a look at the book here

http://www.amazon.com/Etching-Microsystem-Technology-
MichaelK%C3%B6hler/dp/3527295615

Regards,

Denis

2008/9/3 David Roberts :
> To the group,
>
> I need an aluminum oxide etchant that will not attack titanium.
>
> Any experience out there?
>
> Thanks
>
> Dave Roberts