IN-SITU TEM SINTERING OF NANO-SIZED ZRO2 PARTICLES

The sintering behavior of faceted, nano-sized single-crystal particles of ZrO2 has been investigated using in situ transmission electron mic roscope heating techniques. These direct observations have provided ne w information on the morphological and structural evolution of particl es, necks and pores during the sintering process. The results indicate that ZrO2 particle-pairs, which are not attached to other particles a nd not highly constrained by the TEM grid, reorient themselves with re spect to each other during sintering at 890 degrees C. This reorientat ion can be explained in terms of a minimization of the grain-boundary energy between the two coalescing particles. In addition to changes in particle orientation, these experiments show that the topologies of Z rO2 particles and their associated necks evolve during heating. During the in situ TEM heating of these particles, the dynamic motion of ato m clusters (10-100 atoms) on and off of surfaces is observed, as is th e formation and dissolution of ledges and steps on previously smooth f acets. The phenomenon of cluster migration is discussed and the ramifi cations of the results of this study for more highly constrained syste ms of particles (e.g. ceramic green-bodies) are also considered.