Thin films of Zr0.62Al0.38O1.8 are amorphous when deposited at room temperature by rf magnetron sputtering. Crystallization occurs during subsequent annealing in the temperature range of 700-1000 degreesC for times in the range of 10 s-100 h. The crystallite size and the fraction of the sample that had crystallized were determined using x-ray diffraction. The films were found to initially develop a low density of fairly large (similar to8 nm) crystallites, while subsequent heat treatment was found to increase the density rather than the size of the crystallites. Crystallization can be described with a first-order rate equation; the rate constant is exponential in temperature with an effective activation energy of 6.6 eV. Films given a 10 s anneal at < 850 degreesC develop a substantial density of 8 nm grains, making this specific composition an unsuitable candidate for replacing SiO2 as the gate oxide in hyperscaled field-effect transistors.