A comparative study of the influence of milling media on the structural and microstructural changes in monoclinic ZrO2

Structural and microstructural developments of m-ZrO2 during the ball-milling process strongly depend on the type of milling assembly used. Ball-milling with corundum milling assembly cause almost complete amorphization of the starting m-ZrO2, while ball-milling with agate or stainless steel assembly cause a decrease of the volume-averaged domain size up to ∼9 nm or ∼13 nm, respectively. Regardless of the type of milling assembly, a small amount of t-ZrO2 appeared in the milled products. The onset of m-ZrO2 → t-ZrO2 transition occurred only in products ball-milled with stainless steel assembly and resulted in a complete transition after 20 h and probable further transition into c-ZrO2 after prolonged milling. The stabilization of t- and c-ZrO2 in this products resulted from the incorporation of aliovalent cations due to the wear and oxidation of the milling media. The small fraction of t-ZrO2 in the product milled with corundum or agate milling assembly could not be clearly connected with the effect of crystallite size decrease.