## 2 Materials and Methods  
The experimental samples were synthesized using the conventional ceramic solid-state sintering method. Chemically pure powders of zirconium oxide ZrO\({}_{2}\) (Sigma Aldrich, high purity, St. Louis, MO, USA) and cerium oxide CeO\({}_{2}\) (Sigma Aldrich, high purity, St. Louis, MO, USA) with a size of less than 5 \(\upmu\)m were used to prepare the initial blend or charge. The weight of the powder mixture in the initial charge was calculated according to the formula x-CeO\({}_{2}\) + (1 - x)-ZrO\({}_{2}\), where **x** is the mass concentration of CeO\({}_{2}\). A PULVERISETTE 6 classic line planetary mill ([PERSON], Berlin, Germany) was used for the homogenization and dry milling of the initial powders. The process of dry milling was carried out using tungsten carbide grinding bowls and balls at a rotation speed of 250 rpm for 30 min. The milled charge was mixed with an aqueous solution of polyvinyl alcohol to make a molding powder (the residual mass concentration of the polymer was ~1%). The compaction of green pellets was carried out using a hydraulic press with an applied pressure of ~200 MPa in a stainless mold. The resulting green pellets were 12.1 mm in diameter and had a thickness of 0.9-1.1 mm. To obtain dense ceramics, the sintering of green tablets was performed in air. The sintering was performed in a muffle furnace with resistive heaters in the following sequence: heating from room temperature to 400 \({}^{\circ}\)C with a heating rate of 10 \({}^{\circ}\)C/min \(\rightarrow\) exposure at a temperature of 400 \({}^{\circ}\)C for 1 h \(\rightarrow\) heating up to 1500 \({}^{\circ}\)C with a heating rate of 10 \({}^{\circ}\)C/min \(\rightarrow\) sintering at a temperature of 1500 \({}^{\circ}\)C for 5 h \(\rightarrow\) cooling down naturally to room temperature.  
The dimensions and masses of the synthesized tablets were measured using a micrometer and high-precision scales. The elemental composition and morphology of cross-sections of the experimental ceramics were determined by using SEM on a Phenom ProX G6 microscope (ThermoFisher Scientific, Eindhoven, The Netherlands) and energy dispersive X-ray spectroscopy (EDX). Backscattered electron images and EDX spectra were obtained with a 15 kV accelerating voltage. The structural parameters and phase composition of the samples were investigated by the XRD method on a D8 Advance Eco diffractometer (Bruker, Germany). The diffraction pattern measurements were carried out in the Bragg-Brentano geometry using CuK\(\alpha\) radiation: wavelength \(\lambda\) = 1.5406 A, scanning rate of 1.8\({}^{\circ}\)/min, angular range of 20 = 20-90\({}^{\circ}\). The samples were also investigated by Raman spectroscopy on an Enspectr M532 spectrometer (Spectr-M LLC, Chernogolovka, Russia) at a laser wavelength of 532 nm. The microhardness of the ceramics was measured by the Vickers method using a diamond indenter with a load of 0.2 kgf on a MIKON microhardness tester (Duroline-M METKON instruments, Bursa, Turkey) for 10 s. The frequency dependences of the capacitance and dielectric loss tangent tan \(\delta\) were measured using a HIOKI IM3533-01 RLC meter (Hioki E.E Corporation, Singapore) at room temperature. Prior to the dielectric measurements, silver paste contacts were painted to the surface of the tablets on both sides to create a flat capacitor configuration. The calculation of the dielectric permittivity using the measured data was performed with using the formula \(\epsilon^{\prime}=\frac{C\hbar}{\epsilon_{0}S}\), where h denotes the thickness of the tablet, S represents the electrode surface area, C signifies the capacitance, and \(\epsilon_{0}\) is the dielectric constant.