Lattice distortion driving dielectric relaxation frequency and absorbing behavior via electron localization in high-entropy borides

A lattice distortion strategy is employed to tailor the electronic structure. • Electron localization and enhanced dipole moment delay polarization relaxation. • Lattice distortion prolongs the relaxation time by 33.5%. • Absorption peak shifts to X-band with a reflection loss of −50.6 dB. The high electrical conductivity of transition metal borides gives rise to Ku-band dielectric resonance and loss, while causing poor microwave absorption at the X-band. Here, we design a high-entropy (Ti 0.2 Mo 0.2 Nb 0.2 Ta 0.2 Hf 0.2 )B 2 to regulate the electronic structure via lattice distortion engineering, which retards the polarization kinetics and induces a significant redshift of the dielectric response from the Ku-band to the X-band. The results indicate that the (Ti 0.2 Mo 0.2 Nb 0.2 Ta 0.2 Hf 0.2 )B 2 exhibits atomic-scale dislocations (10–16°) between the boron and metal layers. These lattice defects reduce the projected density of states near the Fermi level by 40–50% and promote electron localization. Simultaneously, atomic displacements of 0.0408 Å and 0.1267 Å along the a and c-axes yield an 8.6% enhancement in the dipole moment, which raises the energy barrier for dipole reorientation. And the increased lattice distortion slows the polarization relaxation time (τ) of the boride by 33.5%. As a result, the absorption peak frequency shifts from Ku to X-band and the corresponding RL min increases from −28.6 dB to −50.6 dB. This work establishes a strategy for controlling the dielectric response frequency and absorbing properties at the lattice and atomic scale. A high-entropy strategy is employed to engineer lattice distortion in transition metal borides. The resulting atomic-scale defects promote electron localization and enhance the dipole moment, which delays polarization relaxation. This effect prolongs the relaxation time (τ) by 33.5%, which leads to a shift of the absorption peak to the X-band and a reflection loss of −50.6 dB, establishing a fundamental design principle for controlling absorption frequency. Download: Download high-res image (161KB) Download: Download full-size image