Coating of graphite with a metal alloy Ti–Zr was carried out on a block of graphite sample; the sample was initially dipped in ZrO$_2$ containing a natural starch solution and then proceeded to powder immersion reaction-assisted coating (PIRAC) after drying. Ti powder containing 4 wt% iodine was used as depositing material, and the process was carried out at 850−950$^{\circ}$C for 10 h. The characterizations include X-ray diffraction, scanning electron microscopy and the hardness test. The coating thickness is proportional to the temperature of the PIRAC process, while the percentage of Zr is inversely proportional to the temperature of PIRAC treatment. All the characterizations revealed that the coated layer was a Ti–Zr alloy with hexagonal crystalline symmetry similar to $\alpha$-Ti. An oxidation kinetic assessment at 1000$^{\circ}$C of uncoated graphite shows a burns-off mechanism, while for a coated sample reveals a reaction of Ti with oxygen produces TiO$_2$; the reaction kinetics obey a diffusional mechanism.

Perovskite-based Ba$_{0.5}$Sr$_{0.5}$Fe$_{1–x}$Cu$_x$O$_{3–\delta}$ (BSFCO-$x$, $x = 0–0.2$) was synthesized by sol–gel self-combustionmethod. The crystallinity was evaluated through X-ray diffraction, besides further local structure analysis, using X-ray absorption spectroscopy (XAS) showed a cubic symmetry for $x = 0.05$; 0.10, which was tetragonal at higher values, $x =0.15; 0.20$. XAS analysis predicted the oxidation state (OS) of Cu to be a mixture of 3$+$ and 2$+$, while Fe includes 3$+$ and 4$+$. Conversely, the OS of Fe and Cu in the octahedron site influence the number of an unpair electron that determine the magnetic properties of perovskite. In addition, the magnetization for Ba$_{0.5}$Sr$_{0.5}$FeO$_{3–\delta}$ is 0.172 emu g$^{-1}$, originating from the ferromagnetic ordering Fe$^{3+}$($t_{2g}^3 e_g^2$)–O(2p)–Fe$^{4+}$($t_{2g}^3 e_g^1$) interaction. This effect increase, due to the presence of oxygen vacancy in BSFCO-0.05, which weakens the $d–p$ interaction of Fe-O, while the generation of higher Cu doping to increase the amount of Fe$^{4+}$ leads to a decline in Cu$^{3+}$. Therefore, Cu doping is confirmed to play a role in the paramagnetic–ferromagnetic transition.

This study reports the sintering of Mg$_{0.8}$Zn$_{0.2}$TiO$_3$ (MZT) with an addition of K$_{0.5}$Na$_{0.5}$VO$_3$ (KNV) and Bi$_2$O$_3$. The sintering temperature was performed at 950°C for 4 h and attained a maximum relative density of 97.71% in a composition of 85% mol MZT–10% mol KNV–5% Bi$_2$O$_3$ (MZT85). Structure, microstructure and phase present in the sample were analysed using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. MgZnTiO$_3$, KNaVO$_3$ and BiVO$_4$ were found, besides, the non-crystalline phase was also detected and supposed to be the Bi$_2$O$_3$ melted amorphous phase. Furthermore, with an increase of the lattice parameter and cell volume of samples, it was believed that the sintering aid dissolved partially in the MZT matrix. The electrical properties characterization discovered that at low frequencies (1 Hz–32 MHz) a broader range of space charge polarization was observed, meanwhile, at high frequency (X-band) an enhancement of the permittivity and quality factor Qxf. The relative permittivity ${\varepsilon}_r$ ${\approx}$16.08, the dielectric loss (tan ${\delta}$) ${\sim}$10$^{-2}$ and Qxf = 11.386 GHz at 10 GHz for the MZT85 sample was observed.