Multicomponent ceramics based on transition metals carbides are widely known for their excellent physicomechanical properties and thermal stability. The variation of the elemental composition of multicomponent ceramics provides the required properties. The present study examined the structure and oxidation behavior of (Hf,Zr,Ti,Nb,Mo)C ceramics. Single-phase ceramic solid solution (Hf,Zr,Ti,Nb,Mo)C with FCC structure was obtained by sintering under pressure. It is shown that during the mechanical processing of an equimolar powder mixture of TiC–ZrC–NbC–HfC–Mo₂C carbides, the formation of double and triple solid solutions occurs. The hardness of (Hf,Zr,Ti,Nb,Mo)C ceramic was found at 15 ± 0.8 GPa, compressive ultimate strength—at 1.6 ± 0.1 GPa and fracture toughness—at 4.4 ± 0.1 MPa∙m^1/2. The oxidation behavior of the produced ceramics in an oxygen-containing atmosphere was studied in the range of 25 to 1200 °C by means of high-temperature in situ diffraction. It was demonstrated that (Hf,Zr,Ti,Nb,Mo)C ceramics oxidation is a two-stage process accompanied by the change of oxide layer phase composition. As a possible mechanism of oxidation, diffusion of oxygen into the ceramic bulk results in the formation of a complex oxide layer made of c–(Zr,Hf,Ti,Nb)O₂, m–(Zr,Hf)O₂, Nb₂Zr₆O₁₇ and (Ti,Nb)O₂ was proposed.

The studies on structure, phase composition and thermal properties of (Al₂O₃ - 20 wt% ZrO₂) - ZrW₂O₈ ceramic composites obtained using nanosized, initial powders were conducted. Homogeneously distributed white particles on the polished surface of composites were observed. Phase composition of the composites was represented with corundum, monoclinic ZrO₂ and two modifications of ZrW₂O₈ (tetragonal and cubic). Linear thermal expansion coefficient values of the composites were determined. The difference in experimental and calculated coefficient of thermal expansion values for composites obtained may be attributed to phase transformations, features of the structure, internal stresses due to thermal expansion mismatch, which contribute significantly to thermal expansion of the ceramic composites.

Single-phase ZrW₂O₈ was prepared by hydrothermal synthesis via the decomposition of ZrW₂O₇(OH_1.5, Cl_0.5) · 2H₂O at 570°C. Transmission electron microscopy, in situ high-temperature X-ray diffraction, and thermogravimetric-differential thermal analyses of synthesized ZrW₂O₈ were performed. The morphology of the material was represented as rod-shaped particles having a block structure. The stability fields of ZrW₂O₈ were determined. ZrW₂O₈ demonstrated a negative thermal expansion behavior from 25 to 750°C.