VARIANCES IN THE MEASUREMENT OF CERAMIC POWDER PROPERTIES

Variances in the measurement of properties used to characterize cerami c powders are discussed in the context of the International Energy Age ncy's study, Annex II, Subtask 2, which includes chemical and physical measurements for five powders: two grades of silicon nitride, and one grade each of silicon carbide, silicon, and zirconia. The analysis pr esented here includes results for 39 properties reported by 25 laborat ories using approximately 700 samples of the powders. Measurement unce rtainties are discussed in the contexts of measurement variations with in given laboratories (within-laboratory variance, sometimes called re peatability), among different laboratories (between-laboratory varianc e, also called reproducibility), and among different measurement techn iques (between-methods variance). The analysis shows that the between- laboratory variance tends to be significantly greater than either the within-laboratory or the between-methods variances. The implication of this result is that the most important improvements in powder charact erization measurements may be achieved through the standardization of the measurement methodologies.