Study of the Dissolution of Thin Films of Cerium Oxide by Using a GaPO4 Crystal Microbalance

In this study, microbalance measurements with a GaPO(4) crystal were performed to determine the dissolution rate of cerium oxide thin films at room temperature after a high temperature treatment of the hydroxide precursor Ce(OH)(4) at 700 degrees C. The properties of the GaPO(4) crystal enables gravimetric measurements to be performed after being heated at high temperatures where the classical quartz crystal microbalance irreversibly loses all its piezoelectric properties. The GaPO(4) resonators were calibrated at room temperature by galvanostatic copper deposition before and after a high-temperature treatment, and the sensitivity coefficients K(S) were found to be identical, which proved the high potential of GaPO(4) at high temperatures. However the accuracy of the gravimetric measurements is lower after a high temperature treatment. The rate determining step of the cerium oxide dissolution seems to be the reduction reaction of Ce(IV) to Ce(III), which is carried out by the hydrogen peroxide present in the dissolution medium.