High thermal stability of the dielectric properties of the La2Ti2O7—La4Ti9O24 composites under temperature variation

Abstract

In this work, an experimental and numerical investigation of the dielectric properties in the radio frequency (RF) and microwave (MW) regions of the La₂Ti₂O₇—La₄Ti₉O₂₄ composites was conducted. X-ray diffraction demonstrated that there was a reaction between La₂Ti₂O₇ (LTO) and TiO₂, resulting in the formation of La₄Ti₉O₂₄. Electrical studies in the RF region demonstrated that the composites presented a thermally activated process with activation energy values between 1.50 and 2.30 eV, indicating that the addition provided an increase in activation energy (E_a). In the MW region, an increase in the permittivity (ε'_r) and dielectric loss (tan δ) was observed with the increased presence of La₄Ti₉O₂₄, as well as a change in the temperature coefficient (τ_f). The materials were tested as dielectric resonator antennas (DRA), showing reflection coefficients below –10 dB, realised gain between 4.18 and 4.97 dBi, bandwidth varying from 73 to 207 MHz, and radiation efficiency above 75%. These results show that La₂Ti₂O₇—La₄Ti₉O₂₄ composites are promising candidates for use in electronic circuits in the radiofrequency and microwave regions.