C

Gibbs-Thomson equation

); this driving force is directed to the center of the curvature. In a three-dimensional, single-phase

structure,

it is:

∆

g

=

γ

(

ρ

+

ρ

)

where

γ

is the

grain-boundary energy

, and

ρ

and

ρ

are the principal radii of the boundary curvature. Capillary driving force promotes

normal

and

abnormal grain growth,

as well as

shrinkage

of porous compacts in the course of

sintering

.