High-entropy fluorite oxides (HEFOs) show significant potential for thermal protection applications due to their advantageous combination of low thermal conductivity and high Yong’s modulus. However, the factors influencing its formation have not been well studied, and a systematic method for compositional design has not yet been established. In this paper, the effects of oxygen vacancy concentration (O_vac) and mean cation radius ( $\overline{r}$) on formability of HEFOs were investigated to develop a compositional design approach. The results indicate that an appropriate $\overline{r}$ and O_vac is crucial for promoting the formability of single-phase (Ca_xCe_y1Zr_y2Hf_zSn_zTi_z)O_2−δ HEFOs. High mass/size disorder and an appropriate O_vac (10%) result in (Ca_0.2Ce_0.14Zr_0.12Hf_0.18Sn_0.18Ti_0.18)O_2−δ exhibiting the lowest thermal conductivity of 1.24 W·m⁻¹·K⁻¹. Building upon these insights and employing a valence combination strategy, three new single-phase HEFOs with low thermal conductivity were successfully designed and synthesized, namely, (La_0.28Y_0.28Ce_0.18Zr_0.18W_0.08)O_2−δ, (La_0.3Y_0.3Ce_0.2Nb_0.1Ta_0.1)O_2−δ, and (Yb_0.52Ce_0.12Zr_0.12Sn_0.12Nb_0.12)O_2−δ. This design approach will provide a valuable reference for the design of other high-entropy oxides.

In this paper, cordierite-based porous ceramics with magnetic properties have been firstly in-situ synthesized by using MgO, Al₂O₃, and SiO₂ powders as raw materials and Fe₃O₄ as a functional additive. Combining with the foam freeze casting method, near net size fabrication (total linear shrinkage < 2.86%) of the magnetic porous materials was realized by adjusting the amount of Fe₃O₄. The porosity, compressive strength, and saturation magnetization of the prepared materials were 83.9%–87.8%, 1.51–2.65 MPa, and 1.2–5.8 emu/g, respectively. The phase composition and microstructure evolutions during sintering were investigated briefly. The results showed that the synthesis temperature of cordierite was lowered about 100 ℃ due to the addition of Fe₃O₄. Except for the main phase-cordierite, Mg–Al–Fe spinel and α-Fe₂O₃ also existed in the final materials. The lattice parameters of the Mg–Al–Fe spinel and the amount of α-Fe₂O₃ changed obviously with the change in the sintering temperature and Fe₃O₄ amount, which mainly influenced the magnetic properties of the prepared materials. Thus, a facile fabrication method of the cordierite-based porous ceramics with the magnetic properties has been put forward in this paper.

Single-phase anorthite porous ceramics were in-situ prepared by a foam gel–casting method with CaCO₃, α-Al₂O₃ and SiO₂ as raw materials and environmental-friendly gelatin as a gel. The influence of gelatin amount on the phase composition, microstructure and properties (i.e., porosity, density, compressive strength, and thermal conductivity) of the samples was investigated. The amount of gelatin has no effect on the phase composition of the prepared material, but it affects the properties. The total porosity decreases from 89.7% to 88.0%, the bulk density increases from 0.28 g/cm₃ to 0.33 g/cm₃, the compressive strength increases from 1.02 MPa to 2.54 MPa, and the thermal conductivity increases from 0.038 W/(m·K) to 0.059 W/(m·K) as the gelatin amount increases from 6% to 12%. It is indicated that porous anothite ceramics with a low density, a high strength and a low thermal conductivity could be prepared by this promising method.