Characteristics of bulk and coating in Gd2-xZr2+xO7+0.5x(x = 0.0, 0.5, 1.0) system for thermal barrier coatings

Abstract

Gadolinium zirconate, Gd2Zr2O7, is one of the most versatile oxides among the new thermal-barrier-coating (TBC) materials for replacing conventional yttira-stabilized zirconia (YSZ). Gd2Zr2O7 exhibits excellent properties, such as low thermal conductivity, high thermal expansion coefficient comparable with that of YSZ, and chemical stability at high temperature. In this study, bulk and coating specimens with Gd2-xZr2+xO7+0.5x (x = 0.0, 0.5, 1.0) compositions were fabricated in order to examine the characteristics of this gadolinium zirconate system with different Gd content for TBC applications. Especially, coatings with Gd2-xZr2+xO7+0.5x (x = 0.0, 0.5, 1.0) compositions were produced by suspension plasma spray (SPS) with suspension of raw powder mixtures prepared by planetary milling followed by ball milling. Phase formation, microstructure, and thermal diffusivity were characterized for both sintered and coated specimens. Single phase materials with pyrochlore or fluorite were fabricated by normal sintering as well as SPS coating. In particular, coated specimens showed vertically-separated columnar microstructures with thickness of 400 ~ 600 µm.