Synthesis and electromagnetic properties of one-dimensional La3+-Doped mullite based on first-principles simulation

Abstract One-dimensional La3+-doped mullite of diameter 20–30 nm and length 2–3 μm was prepared by a molten salt method. The electrical properties of La(x)Al(6-x)Si2O13 (x = 0, 0.5%, 1.0%, 2.0%) can be effectively adjusted by the La3+ doping content. The electrical conductivity increased from 1.18 × 10−8 (x = 0) to 2.09 × 10−6 S cm−1 (x = 2.0%). The real part of permittivity was improved from 2.5 (x = 0) to 3.2 (x = 2.0%) in the frequency range 2–18 GHz. The presence of La3+ increased the dielectric loss types and improved the characteristic impedance matching, leading to excellent electromagnetic wave absorption with a minimum reflection loss of −18 dB. First-principles calculations revealed that La doping can decrease the band gap of mullite from 3.677 to 3.541 eV and induce the formation of local dipole moments, which can ultimately improve both the electrical conductivity and the dielectric polarization.