THE MICROSTRUCTURE AND INTERFACES OF INTERMEDIATE LAYERS IN SAPPHIRE BICRYSTALS

The structure of different intermediate layers and their interfaces wa s studied in sapphire bicrystals by high resolution electron microscop y (HREM), selected area electron diffraction (SAED) and energy dispers ive X-ray analysis (EDX). The intermediate layer of Y3Al5O12 between t wo sapphire bicrystal parts, was found to be polycrystalline with thre e major orientations between sapphire and Y3Al5O12. The structure of t he Y3Al5O12/sapphire interfaces is described. Sapphire bicrystals with a multilayer of Y-stabilized ZrO2 (YSZ) and sapphire (Al2O3) as inter mediate layer, are also studied. Recrystallization of the intermediate layers occurred during the solid phase intergrowth of the sapphire bi crystals parts and only an YSZ layer was found as intermediate layer. The misorientation between the consecutive YSZ grains is less than 1.5 degrees. Misfit dislocation and atomic height steps decorate the YSZ/ sapphire interface. (C) 1997 Elsevier Science B.V.