Effect of sintering condition on crystal structure and dielectric properties of novel LuGa_1/3Ti_2/3O_3+x/2 and RGa_1/3Ti_2/3O_3+x/2 (R= Lu_0.2Yb_0.2Tm_0.2Er_0.2Ho_0.2) high-entropy ceramic compounds: A comparative study

Recently, a new series of layered ternary compounds coming from pseudobinary RGaO₃ – R₂Ti₂O₇ have been synthesized and stabilized in out-of-equilibrium (quenching in air) conditions. One of them is the LuGa_1/3Ti_2/3O_3+x/2 (LGTO) compound forming a superstructure of Lu - O and Ga/Ti – O layers stacked along the c-axis. Accordingly, it is imperative to investigate the dielectric behavior in order to envision possible technological applications. Based on this compound, High-Entropy Ceramic (HECs) material has been designed introducing five equimolar rare earth elements in the Lu site with a chemical formula Lu_0.2Yb_0.2Tm_0.2Er_0.2Ho_0.2Ga_1/3Ti_1/3O_3+x/2 (RGTO). The X-ray diffraction pattern shows that the single-phase was successfully formed and then sintering temperatures at 1300, 1400, and 1500 °C were performed to investigate the phase stability. SEM - EDX images show homogeneous cation distribution in both the LuGa_1/3Ti_2/3O_3+x/2 compound and the designed high-entropy ceramic material. A comparison of the band-gap energy estimated from the UV–vis spectra for the pristine and designed High-entropic compounds is reported. Finally, the dielectric properties were analyzed between room temperature up to 500 °C. It is found that the disorder induced by the multicomponent cations in the crystal lattice has no considerable effect on the dielectric constant and in the extrinsic (lattice defects) and intrinsic (charge compensations) dielectric loss tangent. It is argued that the very good dielectric constant (∼150 for LGTO and 21–13 for HECs – RGTO) and loss tangent (>0.01 in both compounds) over a wide range of temperatures along with moderately high values in the band-gap energy (∼3.71 eV for LGTO and ∼3.86 eV for RGTO) make this group of materials good candidates for capacitors and related devices.