Influence of ytterbium- and samarium-oxides codoping on structure and thermal conductivity of zirconate ceramics

✍ Scribed by Zhan-Guo Liu; Jia-Hu Ouyang; Yu Zhou; Jing Li; Xiao-Liang Xia

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 939 KB
• Volume: 29
• Category: Article
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2008.07.033

✦ Synopsis

To increase operating temperature and improve performance of gas-turbine engines, it is urgently needed to develop new thermal barrier oxides with a lower thermal conductivity than 6-8 wt.% yttria-stabilized zirconia. (Yb x Sm 1-x ) 2 Zr 2 O 7 (0 ≤ x ≤ 1.0) ceramics were synthesized by pressurelesssintered at 1700 • C for 10 h in air. The relative density, phase structure, morphology and thermal diffusivity coefficients of (Yb x Sm 1-x ) 2 Zr 2 O 7 ceramics were investigated by the Archimedes method, X-ray diffraction, scanning electron microscopy and laser-flash method. Sm 2 Zr 2 O 7 and (Yb 0.1 Sm 0.9 ) 2 Zr 2 O 7 ceramics exhibit a pyrochlore structure, while (Yb x Sm 1-x ) 2 Zr 2 O 7 (0.3 ≤ x ≤1.0) ceramics have a defect fluorite-type structure. The thermal conductivities of (Yb x Sm 1-x ) 2 Zr 2 O 7 ceramics first gradually decrease with increasing temperature, and then increase slightly above 800 • C due to the increased radiation contribution. YbSmZr 2 O 7 ceramics have the lowest thermal conductivity over the entire temperature range, which is caused by the reduction of cation mean free path in ytterbium-samarium zirconate system.