GRAIN-SIZE DEPENDENCE OF THE TRANSFORMATION TEMPERATURE OF TETRAGONALTO MONOCLINIC PHASE IN ZRO2(Y2O3) CERAMICS

The energetics of transformation from tetragonal to monoclinic phase i n ZrO2(Y2O3) ceramics are investigated using a thermodynamic approach and an expression for transformation temperature dependence on grain s ize is proposed. For fully dense ZrO2(2 mol%Y2O3) ceramics, a quantita tive formula describing the relationship between the starting point of the tetragonal to monoclinic transformation (M(s)) and grain size (d) has been derived on the basis of thermodynamic analysis, i.e. M(s) = 0.34 x 10(6)d(2) - 5.49 x 10(3)d - 4.97d(0.5) - 8.69 x 10(-3)/7.34 x 1 0(3)d(2) + 0.565d Experimental results are compared with theoretical p redictions and general agreement is found. Factors resulting in some d eviation between the experimental and theoretical results are also dis cussed. (C) 1996 Elsevier Science Limited and Techna S.r.l.