KINETICS OF MORPHOLOGICAL CHANGE DURING ANNEALING OF AMORPHOUS YTTRIA

We report a time-at-temperature study of air annealing at 700-degrees-C of amorphous yttria films sputter deposited on fused silica. The results show that crystallization was limited (7%). A striking morphological change involved the formation of 2.5-mu-m-maximum diameter globules. By comparing changes in globule number with maximum diameter, the time-at-temperature ranges for which nucleation + growth and growth + coarsening processes occurred was determined. The globule formation rate initially followed an Arrhenius curve: dN(V)/dt = (4 X 10(5)/cc s)exp[ - 0.28 x 10(-3)/s)t]. The activation energy estimated for globule formation was close to that for Y diffusion in yttria.