TEM OBSERVATION OF REACTION AT THE INTERFACE BETWEEN YTTRIA-DOPED CERIA AND YTTRIA-STABILIZED ZIRCONIA

Interfacial reaction between yttria-stabilized zirconia (YSZ) and yttr ia-doped ceria (YDC) phases was analyzed by X-ray diffraction and high -resolution transmission electron microscopy. An X-ray diffraction pat tern indicated that the mixture of YSZ and YDC consisted of their orig inal phases after heating at 1100 degrees C, whereas a solid state rea ction occurred between them at higher temperatures. The solid state re action proceeded as the Ce component was dissolved into the cubic YSZ phase, with an expense in the amount of the cubic YDC phase. The compl etion of the reaction gave a single cubic fluorite phase of Y-doped zi rconia-ceria (YCZ) solid solution at 1500 degrees C or high temperatur es. A high-resolution transmission electron microscopic analysis suppo rted this reaction process. No solid state reaction was observable at the interface of the ceria and zirconia particles on heating at 1100 d egrees C. Although the YDC and YSZ particles are tightly combined at t he interface, the lattice kept its original array and orientation. The sample heated at 1300 degrees C contained particles undergoing solid state reaction. The YDC phase was observed in the interface region of the zirconia side. The surface region of YCZ which faced the ceria par ticle contained a number of defects. The formation of defects is accom panied by the dissolution of ceria in the zirconia lattice and the lat tice of zirconia was distorted to fit to the orientation of the ceria lattice. After heating at 1500 degrees C the sample consisted of a hom ogeneous YCZ phase. (C) 1997 Academic Press.