Role of Grain Boundaries in Sintering.

During sintering, grain boundaries act either as sinks or as diffusion paths for lattice vacancies. Thus the configuration of the grain boundaries will have an important effect on the rate of sintering. Grain growth during sintering changes the configuration of grain boundaries relative to pores and thus may markedly influence the shrinkage rate; for example, for uniformly distributed pores the shrinkage rate will increase as the grain size decreases. Impurity additions will increase the sintering rate if they increase diffusion rates, but they may also increase sintering rates by impeding grain-boundary movement. Some experimental evidence is presented to support these conclusions.