Experimental study of phase transformation and specific heat of ternary zirconia-based oxides using differential scanning calorimetry

Phase transformation and specific heat of five ternary zirconia-based oxides were studied using differential scanning calorimetry (DSC). The ternary oxides were fabricated by doping 7YSZ (3.945 mol.% Y(2)O(3)-ZrO(2))with pentavalent oxides Ta(2)O(5) and Nb(2)O(5), trivalentoxides Sc(2)O(3) and Yb(2)O(3), and tetravalent oxide CeO(2). The addition of pentavalent oxides to 7YSZ increased the formation of monoclinic phase upon cooling in comparison to 7YSZ. The phase transformation from monoclinic phase to tetragonal phase took place in the temperature range of 500-700 degrees C. The incorporation of trivalent dopants effectively stabilized cubic phase to room temperature; the cubic phase, however, seemed to experience an order to disorder transition during subsequent heating and cooling cycle. Tetravalent oxide addition to 7YSZ increased the formation of tetragonal phase as compared to 7YSZ and no phase transformation was observed between 100 and 1400 degrees C. The specific heat values for the ternary oxides were measured from room temperature to 1000 degrees C. The experimentally determined values were compared to that calculated based on the constituent oxides in the system using Neumann-Kopp rule and the discrepancies were further discussed in this study. (C) 2009 Elsevier B.V. All rights reserved.