A novel use of constrained sintering to determine the viscous Poisson’s ratio of densifying materials

This paper describes a novel technique, based on the concept of pressureless constrained sintering and the viscous analogy, for determining the viscous Poisson’s ratio of sintering materials. The method involves measuring the sintering rate of a free-sintered specimen, and a specimen constrained by two non-sintering layers. Representative data for a low temperature co-fired ceramic (LTCC) material are reported. The viscous Poisson’s ratio varied from 0.25 at ~ 74% density to about 0.45 at ~ 93%, which agrees well with model predictions. The method applies only during the intermediate stage of densification, because the material is viscous during this period of sintering.