Enhanced doping effects of multielement on anisotropic thermal expansion in ZrO ₂ with new compositions

Abstract

Abstract 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% Y 2 O 3 stabilized ZrO 2 (8YSZ) will contribute to the decrease in thermal expansion mismatch between a typical ceramic 8YSZ (10 ~ 11 × 10 −6 °C −1 ) top coat and a metal alloy based bond coat such as NiCrAlY (14 ~ 17×10 −6 °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 Dy 3+ , Al 3+ , and Ce 4+ ‐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 ZrO 2 . The calculated lattice energy becomes smaller with the incorporation of Dy 3+ , Al 3+ , and Ce 4+ ions, which corresponds strongly to the increase in CTE. The crystalline size is reduced due to the incorporation of the Al 3+ and Ce 4+ , whereas the sintering resistance is enhanced ascribed to the addition of Dy 3+ and Al 3+ . Doping Dy 3+ , Al 3+ , and Ce 4+ cations to YSZ increased the CTE value of YSZ and for Dy 0.03 Y 0.075 Zr 0.895 O 1.948 , the CTE is 12.494 × 10 −6 °C −1 at 900°C, which has an 11% increase, as compared with that of 8YSZ.

Topics & Concepts