Electron diffraction of yttrium iron oxide nanocrystals prepared by the alkoxide method

Yttrium iron garnet (YIG) ultrafine particles of several nanometers in diam eter were prepared by the alkoxide method. The phase transformation of the particles during the course of calcination was studied in detail by transmi ssion electron microscopy. A small fraction of the uncalcined amorphous par ticles was spontaneously crystallized into epsilon-Fe2O3. The amorphous pha se undergoes incomplete crystallization by forming an intermediate phase at 660 degrees C calcination. Complete crystallization to YIG does not occur at temperatures lower than 675 degrees C. A small amount of YFeO3 and Fe32Y 12O2 (intermetallic compound) nanocrystals were also formed at calcination temperatures as low as 660 degrees C. In selected area electron diffraction (SAED) experiment of the present YFeO3 nanocrystals, we found a peculiar s election rule; we observed strong diffraction from the lattice planes, (i,j , k), if the sum, i + j + k was odd, and weak or no diffraction from other planes. In the SAED experiment of YIG nanocrystals, we found that the diffr action rings fluctuated in the radial direction. (C) 2000 Elsevier Science B.V. All rights reserved.