Evidence was obtained that c-type rare earth M(2)O(3) stabilized ZrO2 in the tetragonal phase via oxygen coordination between the M(2)O(3) molecule and the ZrO2 unit cell. The ratio for 100% stabilization was calculated to be 2.7 mol% M(2)O(3) stabilizer. This was experimentally proved by using the co-decomposition process to obtain 100% tetragonal stabilization efficiency. It has also been established that stabilization is dependant upon the average Zr-O bond length of 226 pm as a parameter and not necessarily of an exact radius varying between 206 pm and 246 pm.