Investigation of dielectric properties of a Li₄Ti₅O₁₂ ceramic matrix for microwave temperature sensing applications

In this article, the dielectric properties of a Li₄Ti₅O₁₂ (LTO) ceramic at the radio frequency (RF) and microwave (MW) regions were evaluated. X-ray diffraction showed that LTO was obtained without the presence of spurious and/or secondary phases. Complex impedance spectroscopy (CIS) analysis was conducted, whereas an activation energy (E_a) of 0.88 eV was observed. The temperature capacitance coefficient (TCC) was also calculated and demonstrated that LTO could be employed as a Class 1 ceramic capacitor. In the MW region, LTO presented ε’_r = 25.4, tan δ = 5.7 × 10^–4, and τ_f = -14.5 ppmºC⁻¹, values that are interesting for devices that operate in the MW region. Numerical simulation demonstrated values of a realized gain of 4.78 dBi, a bandwidth of 227 MHz, and a radiation efficiency of 98%. Moreover, LTO was evaluated as a temperature sensor operating in the MW region and demonstrated a sensitivity of -0.06 MHz ºC⁻¹. The values presented demonstrate that LTO could be employed in devices that operate in RF and MW regions.