Crystallization phenomena in β-Ga2O3 investigated by positron annihilation spectroscopy and X-ray diffraction analysis

Samples of single- and polycrystalline beta-Ga2O3, undoped and doped with Tb3+ or Dy3+ were investigated by positron lifetime spectroscopy and by X-ray diffraction analysis. The positron annihilation data show that there are more large open-volume defects in the samples sintered at 800 degreesC than in the samples sintered at higher temperatures (1200 and 1500 degreesC). Also, intergranular precipitation of second-phase particles (crystallites) of RE3Ga5O12 is suggested to occur in the doped samples sintered at 1200 and 1500 degreesC, and is confirmed by the X-ray diffraction data. These second-phase crystallites are inclined to precipitate either along grain boundaries or at surfaces of pores. For the samples sintered at 800 degreesC, most rare earth ions remain in the oxide forms and the second phase of RE3Ga5O12 is not nucleated. This indicates that a sintering temperature of 800 degreesC may not be high enough to trigger the growth of the second phase of RE3Ga5O12. Crown Copyright (C) Published by Elsevier Science B.V. All rights reserved.