y-tzp has both high sinterability and superior mechanical properties, but the fracture strength is degraded by annealing at such low temperatures as 100 approximately 300 $degree$ c. in order to improve the heat degradation of tzp containing 3 mol-y//2o//3, a fabrication technique for surface modification of tzp was developed the method consists of infiltrating a porous powder compact with open porosity of about 53 by the application of y(no//3)//3 solution using a suitable brush and subsequently firing at 1400 $degree$ c in air to decompose the infiltrant and to densify the powder compact y-tzp surface-modified by infiltration of y(no//3)//3 solution did not show the tetragonal to monoclinic zirconia transformation after aging in hot water of 200 $degree$ c for 100 hours at all even through the examination by thin film x-ray diffraction. therefore, this infiltration technique may prove to be very valuable when designing tzp for structural applications. (author abstract) 20 refs in japanese