Improvement on thermophysical and mechanincal properties of LaMgAl11O19 magnetoplumbite by Nd2O3 and Sc2O3 co-doping

LaMgAl11O19-type magnetoplumbite holds great promise to be used above 1300 degrees C as thermal barrier coatings (TBCs), but its practical application has been restricted because of inferior thermophysical properties. Herein, we focus on optimizing the thermophysical properties of LaMgAl11O19 by simultaneously substituting La3+ and Al3+ ions with Nd3+ and Sc3+ ions, respectively. Results show that the effects of co-substitution on reducing thermal conductivity are pronounced. The thermal conductivities of La1-xNdxMgAl11-xScxO19 (x = 0, 0.1, 0.2, 0.3) ceramics decrease progressively with dopant concentration and a lowest thermal conductivity of 2.04 W/(m.K) is achieved with x = 0.3 at 1000 degrees C, which is a value superior to pure LMA and even lower than YSZ. The mechanisms behind the lowered thermal conductivity are investigated. Increase of the thermal expansion coefficient is also realized (8.53 x 10(-6) K-1 for pure LMA, 9.07 x 10(-6) K-1 for x = 0.3, 1300 degrees C). Most importantly, Nd3+ and Sc3+ combination doping indeed facilitates mechanical properties of La1-xNdxMgAl11-xScxO19 solid solutions as well. It should be noted that Sc3+ doping at Al3+ site plays more effective role in improving thermal properties than Nd3+ does at La3+ site. This work provides a path to simultaneously integrate low thermal conductivity, good phase stability, moderate thermal expansion behavior and excellent mechanical properties on LMA for the next generation TBCs.

Automated summary

By simultaneously substituting La3+ and Al3+ ions with Nd3+ and Sc3+ ions, the thermal conductivity of LaMgAl11O19 ceramics was successfully reduced, accompanied by an increase in thermal expansion coefficient and enhanced mechanical properties.