By focusing on the similarities between the three stages of sintering, a single equation is derived that quantifies sintering as a continuous process from beginning to end. The microstructure is characterized by two separate parameters representing geometry and scale. The dimensionless geometry parameter, denoted r, comprises five scaling factors that relate specific microstructural features (e.g., surface curvature) to the scale (grain diameter). Calculations of r from experimental data show (a) agreement with computer simulations of initial-stage sintering, (b) the effect of surface diffusion on I?, and (c) changes in r with microstructural evolution during sintering. Application of the model to the design of firing schedules and the study of microstructural geometry effects on sintering is discussed. [

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Thermodynamic calculations predict, and experiments verify, that Y Ba2Cuj0,-6 (123) powder is unstable in the presence of NO,-containing aerosol reactor exhaust gases at temperatures below about 600°C. Powders collected above the stability temperature are single-phase 123, while powders collected at lower temperature contain Ba(N03 j 2 formed by reaction of the powder with NO, after exit from the hot zone. [