Structures, and Thermophysical Properties Characterizations of (La1-xHox)3NbO7 Solid Solutions as Thermal Barrier Coatings

A sequence of (La 1-x Ho x ) 3 NbO 7 solid solutions were fabricated in this work, which were studied as candidate for thermal insulation materials. The lattices were identified via XRD, when SEM and EDS were used to characterize the microstructures and element distributions. The results showed that the highest modulus, hardness, and toughness of (La 1-x Ho x ) 3 NbO 7 were 196 GPa, 9.2 GPa, and 1.6 MPa m 1/2 , respectively, and they accorded with the mechanical property requirements. Also, a low thermal conductivity (1.06 W m −1 K −1 ) and high thermal expansion coefficients (TECs: 11.3 × 10 −6 K −1 ) were simultaneously realized in (La 3/6 Ho 3/6 ) 3 NbO 7 , at high temperatures. No phase transition was detected up to 1,200°C, which proved their good high-temperature lattice stability. The intense anharmonic lattice vibrations might contribute to the outstanding thermal properties of (La 1-x Ho x ) 3 NbO 7 ceramics. The suitable modulus, high hardness, low thermal conductivity, and high TECs of (La 1-x Ho x ) 3 NbO 7 solid solutions proclaimed that they were exceptional thermal insulation ceramics.