Thermal diffusivity characterization of europium zirconate, cerate and hafnate

The following paper presents study on synthesis and thermal diffusivity of europium zirconate, cerate and hafnate as a new types of materials with pyrochlore or fluorite type of lattice, dedicated to replacement of conventional 8YSZ (yttria stabilized zirconia) in TBC (thermal barrier coatings) systems for aircraft gas turbines. All materials were synthesized via solid-state reaction (SSR) preceded preparation of powder mixtures (mechanical milling in ethanol). The feedstock powders were characterized by analysis of crystallite size, particle size distribution and phase composition. On the base of DSC measurements, the parameters of high temperature sintering were selected (1350 °C/2 h/15 MPa). Structural characterization of obtained materials inclusive analysis of morphology, chemical and phase composition of sinters was performed. Thermal diffusivity was measured in temperature range 25÷1400 °C by laser flash analysis (LFA). The obtained materials with pyrochlore and fluorite type of lattice exhibit lower thermal diffusivity compared to that of yttria-stabilized zirconia at high temperatures. In particular, the most promising material in view of insulating properties is Eu₂Ce₂O₇, which exhibit much lower thermal diffusivity than Eu₂Zr₂O₇ and Eu₂Hf₂O₇, especially at temperature higher than 1000 °C. However, in temperature range 25–700 °C, europium hafnate and zirconate exhibit lower thermal diffusivity compared to that of europium cerate and 8YSZ.