ABSTRACT
Our discussion of the sintering process has so far been concerned with solid-state sintering, in which the material remains entirely in the solid state. In many ceramic systems, the formation of a liquid phase is commonly used to assist in the sintering and microstructural evolution. Usually the purpose of
liquid-phase sintering
is to enhance densification rates, to achieve accelerated grain growth, or to produce specific grain boundary properties. The distribution of the liquid phase and of the resulting solidified phases produced on cooling after densification is critical to achieving the required properties of the sintered material. Commonly, the amount of liquid formed during sintering is small, typically less than a few volume percent (vol%), which can make precise control of the liquid composition difficult. In some systems, such as Al
O
, the amount of liquid phase can be very small indeed and so difficult to detect that many studies that were believed to involve solid-state sintering actually involved liquid silicate phases, as later revealed by careful high-resolution transmission electron microscopy.
