To fully densify a powder compact, we should avoid two things: (i) entrapment of insoluble gases within pores and (ii) entrapment of isolated pores within grains. This paper describes general directions for promoting full densification in view of the above two points. Emphasis is placed on ways to potentially prevent pore entrapment in terms of grain growth control. Currently available techniques that can enhance densification while suppressing grain growth are briefly described, and their major mechanisms are discussed.
Keywords: densification; entrapped gases; fast firing; flash sintering; grain boundary; grain growth; microstructural evolution; pore entrapment; spark plasma sintering; two-step sintering.