Dependence of crystal structure on mechanical and thermophysical properties of magnetoplumbite‐type LnMgAl₁₁O₁₉ ceramics with substitution of Ln³⁺ Ions

Abstract

Lanthanum hexaaluminate is a promising candidate to establish yttria partially stabilized zirconia as a thermal barrier coating material for super alloy due to their remarkable stability and thermophysical performance. In order to understand the relationship between the structure and properties and gain new low thermal conducting materials, the LnMgAl11O19 (LnMA, Ln: La, Pr, Nd, Sm, Eu, Gd) materials were synthesized firstly and further used to produce the LnMA ceramics. With the increasing relative atomic mass of the replaced Ln3+ ions from La to Gd, the lattice parameters and grain sizes of the LnMA platelets decrease, while the mechanical properties increase, and the thermal physic properties decrease. The GdMgAl11O19 ceramics obtain the lowest thermal conductivity with the value of 1.91‐1.78 W/m K in the range from room temperature to 800°C, which could be considered as a promising candidate for application in thermal barrier coating materials. These results could further provide reference for developing novel materials lower thermal conductivity.