The only commercially available ZTA powders I know is from Taimicron in Japan with 16 or 20 wt-% zirconia (probably 3Y-TZP). They are extremely fine grained and expensive and we have never tried them yet. From my point of view it makes much more sense to prepare your powder blends on your own depending on your specific requirements. Choice of starting powders, zirconia fraction and stabilization have a extremely strong influence on mechanical properties of ZTA.

see:

doi:10.1016/j.jeurceramsoc.2012.02.057

http://dx.doi.org/10.1016/j.jeurceramsoc.2012.06.019

Thanks Frank for your comments.