Journal of the American Ceramic Society, Vol.103, No.10, 5881-5890, 2020
Enhanced doping effects of multielement on anisotropic thermal expansion in ZrO2 with new compositions
Coefficient of thermal expansion (CTE) of a solid material plays a critical role for a variety of high temperature applications such as thermal barrier coating (TBC) systems during the thermal cycling process. Ceramics contain ionic bonds; hence they tend to exhibit lower CTE values than alloys/metals. Developing new ceramic thermal barrier materials using promising dopants and compositions that have higher CTE values than the conventional 6-8 wt% Y2O3 stabilized ZrO2(8YSZ) will contribute to the decrease in thermal expansion mismatch between a typical ceramic 8YSZ (10 similar to 11 x 10(-6)degrees C-1) top coat and a metal alloy based bond coat such as NiCrAlY (14 similar to 17x10(-6)degrees C-1, Padture et al.,Science, 2002;296:280-4; Liang et al., J Mater Sci Technol, 2011;27(5):408-14), which is highly desirable. This work reports design, modeling, synthesis, and characterization of promising new compositions based on Dy3+, Al3+, and Ce4+-doped YSZ that consist of the tetragonal structure and have an enhanced thermal expansion than 8YSZ. The intrinsic CTE at the atomic level has been investigated via molecular dynamics (MD) simulation. The atomic scale analysis provides new insights into the enhanced doping effects of multiple trivalent and tetravalent cations on the lattice structure, lattice energy, and thermal expansion in ZrO2. The calculated lattice energy becomes smaller with the incorporation of Dy3+, Al3+, and Ce4+ ions, which corresponds strongly to the increase in CTE. The crystalline size is reduced due to the incorporation of the Al3+ and Ce4+, whereas the sintering resistance is enhanced ascribed to the addition of Dy3+ and Al3+. Doping Dy3+, Al3+, and Ce4+ cations to YSZ increased the CTE value of YSZ and for Dy0.03Y0.075Zr0.895O1.948, the CTE is 12.494 x 10(-6)degrees C(-1)at 900 degrees C, which has an 11% increase, as compared with that of 8YSZ.