Sintering behavior, flexural strength, thermal conductivity and dielectric properties of novel Y2O3-LiF co-doped AlN ceramics

This study systematically investigates the influence of Y 2 O 3 content on the microstructure, thermal conductivity, flexural strength, and dielectric properties of AlN ceramics co-doped with 2 wt% LiF. XRD and Rietveld refinement confirmed the hexagonal crystal structure for all compositions, with the Y2F2 sample exhibiting a distinct lattice contraction. SEM analysis revealed a steady​ decrease in grain size and a morphological evolution​ of the secondary phase at grain boundaries from a discontinuous to a continuous state with increasing Y 2 O 3 . TEM further demonstrated that the Y2F2 composition yielded the most favorable microstructure, characterized by minimal interface defects and a well-ordered transition zone at the grain boundary triple junctions. Consequently,​ the sample with 2 wt% Y 2 O 3 (Y2F2) delivered optimal overall performance:​ a thermal conductivity of 231.26 W m −1  K −1 , a bending strength of 302 MPa, a dielectric constant of 8.396 (at 1 MHz) with a low loss factor of 1.4 × 10 −3 , and an activation energy of 1.04 eV. These results identify 2 wt% as the critical Y 2 O 3 content that balances oxygen gettering and lattice incorporation, leading to a synergistic optimization of properties.