Effects of 7YSZ doping on properties of lanthanum cerate coatings

Lanthanum cerate(La2Ce2O7, LC) is a typically material with fluorite structure, which an attractive new generation TBC material due to low thermal conductivity, relative higher thermal expansion coefficient and excellent high temperature phase stability. Sintering-resistance of LC sharply decreased above 1518K is the main reason for LC as new TBC with target service temperature above 1573K. The effect of 7YSZ doping LC on thermal physical properties, sintering-resistance were studied. La2Ce2.5O8 sprayed powders doped with 1 similar to 10mass% 7YSZ were synthesized by solid-phase synthesis and agglomerated-sintering method, and ceramic coatings were prepared in the same process condition. The LC coatings doped with 7YSZ retained lower thermal conductivity (0.7 similar to 0.8W.m(-1)K(-1) at 1573K with about 80% relative density) compare to the LC coating (0.723W.m(-1)K(-1)at 1573K with 75.4% relative density), and also exhibited excellent phase stability between room temperature and 1773K. Dilatometric measurements(1573K, 5h) of the plasma-sprayed coatings showed that lower sintering rate for LC coatings with 5mass%-10mass% YSZ doped, shrinkage rate decreased from 0.59%(LC coating) to 0.1 similar to 0.25%(5mass%10-mass% doped).