Initial Sintering with Constant Rates of Heating

Initial sintering of several materials was studied by measuring powder compact densification at constant rates of heating (CRH). The CRH technique was extremely sensitive to the particle size distribution and other characteristics of the compacts. Although the CRH method circumvents several problems encountered in isothermal studies, it cannot be used to identify the mechanism of diffusion. Using the method on carefully prepared alumina powder compacts and assuming a grain‐boundary diffusion mechanism, an activation energy of 115±10 kcal/mol was obtained. Zirconia (yttria‐stabilized) and titania also exhibited a single densification mechanism with diffusion coefficients which correlate well with values obtained by isothermal measurements.