A high thrust-to-weight ratio imposes stricter requirements on thermal barrier coating for gas turbine blades. High-entropy pyrochlore oxides are particularly attractive due to their excellent performance. In this paper, a series of high-entropy oxides with the general formula La-2(Yb0.25(1-x)Y0.25(1-x)ZrxNb0.25(1-x)Ta0.25(1-x))(2)O-7 (x = 0 similar to 0.3) were designed and fabricated, and their phase composition, microstructure, and key properties were investigated. With increasing Zr4+ content, the phase composition transitions from a mixture of pyrochlore and secondary phase to a dual-phase pyrochlore, and finally to single-phase high-entropy pyrochlore oxides. Single-phase HEPOs La-2(Yb0.25(1-x)Y0.25(1-x)ZrxNb0.25(1-x)Ta0.25(1-x))(2)O-7 (x = 0.2 similar to 0.3) possess low thermal conductivity, a high coefficient of thermal expansion, and excellent high-temperature phase stability. Specifically, La-2(Yb0.1875Y0.1875Zr0.25Nb0.1875Ta0.1875)(2)O-7 exhibits a thermal conductivity as low as 0.96 W/(m & centerdot;K), and a coefficient of thermal expansion of 9.8 & times; 10(-6) K-1. After 120 h of heat treatment at 1450 degrees C, its grain growth rate is only 11.69%. These properties indicate that La-2(Yb0.1875Y0.1875Zr0.25Nb0.1875Ta0.1875)(2)O-7 has great potential for applications in the field of thermal barrier coating.

Printable mesoscopic perovskite solar cells (MPSCs) hold significant potential as a low-cost photovoltaic technology. In this study, iron oxide (Fe3O4) modified carbon electrode were innovatively used to optimize the interfacial performance in MPSCs. The devices with different mass ratios of Fe3O4 to graphite were fabricated by printing method. With the multi-effects of the Fe3O4-modified CEs, a 16.43% efficiency of the device (CFe3O4-0.15) was achieved, which was 10.6% higher than the control device using standard carbon electrodes. Simultaneously, the device (C-Fe3O4-0.15) retained 96% of their highest PCE, which was higher than 72% of the control device after 1000 h at room temperature condition. This research provides a scalable solution for enhancing the stability of MPSCs through electrode engineering.

Water evaporation-induced electricity generator (WEG) is a highly promising approach to harness the power of water evaporation. In this study, a robust TiO2-C bi-layer WEG (TC-WEG) based on a conductive glass (FTO) substrate has been developed through a simple method in which the TiO2 layer was made by the doctor-blade method and the carbon black (CB) layer by the flaring method. The open-circuit voltages (Voc) and shortcircuit currents (Isc) of the TC-WEGs exhibited a near-linear relationship to the evaporative height and width of the TC-WEGs respectively. The 1.5 cm by 8 cm TC-WEG could consistently produce a high V oc over 1.5 V and an I sc exceeding 400 nA under ambient conditions. Despite prolonged exposure to water immersion, the TC-WEG kept its structural integrity and ensured a consistent and stable electrical output without any degradation. The TC-WEG, characterized by its easy fabrication and high cost efficiency, possesses substantial practical potential for harnessing renewable energy sources.

High-entropy fluorite oxides (HEFOs) demonstrate a broader application prospect as thermal insulators due to their outstanding properties. Currently, the synthesized HEFOs contain at least one type of rare earth elements (REEs), which are listed as critical materials by some international institutions. To explore the possibility of rareearth-free HEFOs, first-principals calculations and the solid state reaction method were employed by adjusting the mean cation radius (r) and oxygen vacancy concentration (Ovac) of (Ca,Zr,Hf,Sn,Ti)O2-delta. The first-principles calculations results indicate that the Gibbs free energy change (Delta G(T)) could be controlled by adjusting r and Ovac, and the Delta G(T) of (Ca0.2Zr0.2Hf0.2Sn0.2Ti0.2)O2-delta was slightly higher than zero. After further detailed composition design, a novel rare-earth-free HEFOs composed of(Ca0.2Zr0.28Hf0.28Sn0.19Ti0.05)O2-delta with a higher r has been successfully synthesized for the first time. Its thermal conductivity is 1.22 W & sdot;m-1 & sdot;K-1, which is much lower than that of most HEFOs mainly composed of REEs.

A series of (Y, Yb, Zr, Hf, Sn, W)O 2−δ high‐entropy ceramics with varying mole fraction of main elements were synthesized for the first time through the solid‐state reaction synthesis method. The microstructure, phase composition, and properties of the prepared materials were thoroughly analyzed and tested. The results indicate that the phase composition transformed from a single‐phase fluorite structure to a single‐phase C‐type rare earth sesquioxide structure as the mole fraction of +3 cations increases. The thermal conductivity of the prepared high‐entropy ceramics with porosity of 49.8%–50.1% is very low ranging from 0.33 to 0.37 W·m −1 ·K −1 . Among them, the single‐phase C‐type rare earth sesquioxide with a higher oxygen vacancy concentration was employed as a catalyst in the CO 2 hydrogenation reaction, attaining a high CO 2 conversion rate of 82.0%. The obtained results have deepened understanding of the role of oxygen vacancies and have important guiding significance for the study of high‐entropy oxides with fluorite derived structures.

SiC porous ceramic carriers with adjustable porosity of 79.9%-90.7% were prepared by foam gel-casting forming and carbothermal reduction reaction sintering, using industrial waste fine-grained iron tailings and graphite powder as raw materials. Then paraffin/SiC shape-stable phase change materials were prepared by spontaneous infiltration employing paraffin as phase change material. Thermal conductivity of the SiC carriers (0.17-0.31 W/ m center dot K) is 2.7-3.7 times higher than that of iron tailings porous ceramics with the same porosity. A thermal conductivity model of the SiC carrier is established and verified by experimental data. Phase composition, microstructure, molecular structure, mechanical properties and thermal properties of the shape-stable phase change materials were characterized by XRD, SEM, FT-IR, WDW, Hot Disk and DSC, respectively. There is only a physical combination between paraffin and SiC carriers. The compressive strength of the shape-stable phase change materials (2.0-2.3 MPa), weight loss and latent heat loss are less than 5% and 4.7% after 100 thermal cycles, respectively, which can meet the application requirements as a functional material. Thermal conductivity of the shape-stable phase change materials (0.7-0.73 W/m center dot K) is significantly improved, a latent heat of 138.5 J/g, and the efficiency of energy storage and release is 2.3-3.3 times as good as than that of paraffin, suggesting that this material is capable of recycling and reusing waste heat as a highly efficient thermal energy storage system.

Printable HTM-free (HTM = hole -transporting material) mesoporous carbon -based perovskite solar cells (C-PSCs) are one of the most promising technologies. In this study, a high -quality chlorinated mesoscopic TiO2 (m-TiO2) film was obtained by hydrochloric acid (HCl) wet chemical process and applied in C-PSCs based on TiO2/ZrO2/ (5-AVA)x(MA)1-xPbI3/C structures. Experimental results show that the PCE of chlorinated m-TiO2 C-PSCs greatly improved. Based on (5-AVA)x(MA)1-xPbI3, C-PSCs with TiO2 ETL treated with HCl aqueous solution achieved an average photovoltaic conversion efficiency of 9.36 %, which is an increase of 7.96 % in comparison with the efficiency of the device using unmodified TiO2 ETL, while the Voc and the Jsc were increased by 3.63 % and 2.63 %, respectively. In a 30 -day aging test, C-PSCs based on (5-AVA)x(MA)1-xPbI3 and TiO2-HCl 1 exhibited excellent stability under ambient air conditions.

Many factors impact the formability of single phase high-entropy pyrochlore ceramics (HEPCs) which become a research hotspot owing to their excellent properties. To investigate the effect of size disorder, two combinations with same mixing entropy and different size disorder were designed, thermodynamic analysis of first-principles calculations and experimental research were conducted in this paper. The calculation results reveal that the enthalpy change decreases significantly with the decrease of size disorder, promoting the synthesis of singlephase high-entropy pyrochlore. The experimental results prove that the combination with lower size disorder leads to single-phase HEPCs, and the prepared material exhibits low thermal conductivity (1.68 W/(m & sdot; K)) and low theoretical density (5.73 g/cm 3 ).

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 (Ovac) and mean cation radius (r¯) on formability of HEFOs were investigated to develop a compositional design approach. The results indicate that an appropriate r¯ and Ovac is crucial for promoting the formability of single-phase (CaxCey1Zry2HfzSnzTiz)O2−δ HEFOs. High mass/size disorder and an appropriate Ovac (10%) result in (Ca0.2Ce0.14Zr0.12Hf0.18Sn0.18Ti0.18)O2−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, (La0.28Y0.28Ce0.18Zr0.18W0.08)O2−δ, (La0.3Y0.3Ce0.2Nb0.1Ta0.1)O2−δ, and (Yb0.52Ce0.12Zr0.12Sn0.12Nb0.12)O2−δ. This design approach will provide a valuable reference for the design of other high-entropy oxides.

In this study, fine-grained iron tailings, graphite, and SiC powder were used as raw materials to explore a novel strategy for developing SiC porous ceramics from industrial waste. By optimizing the conditions of carbothermal reduction reaction between iron tailings and graphite, the formation and growth of SiC grains were enhanced. The effects of sintering parameters on mechanical and thermal conductivity properties were investigated with adjusting the SiC content in raw materials. SiC porous ceramics with three-dimensional porous structure, adjustable porosity (77.2-91.6%), low bulk density (0.31-0.51 g/cm3), enhanced thermal conductivity (0.22-0.54 W/(m & sdot;K)) and compressive strength (0.09-1.61 MPa), and high permeability of deionized water (3.03x10 - 11-21.03x10- 11 m2) are obtained by foam gel-casting forming and reactive sintering process. Meeting industrial requirements for tailings reuse, low cost and high throughput fabrication, this new material combines the properties of high strength and high thermal conductivity of SiC with clay minerals, and has broad prospects in applications of composite phase change materials, lightweight refractory bricks, filter materials and so on.

In this paper, a series of (Ce0.2Zr0.2Ti0.2Sn0.2Y0.2-xCax)O2-delta (x = 0-0.2) high-entropy of compositionally-complex ceramics were prepared using solid-state reaction method. The results showed that the content of Ca2+ had significant effects on the phase composition, microstructure and properties of the prepared materials. As Ca2+ content increased, single-phase fluorite was easier to form. When x <= 0.05, materials contained dual-phase of fluorite and pyrochlore structures. When x >= 0.075, the prepared materials showed single-phase fluorite structure, which indicated that high-entropy fluorite ceramics (HEFCs) could be prepared under this condition. When Ca2+ content increased from 0.075 to 0.2, grain size of HEFCs decreased, and relative density decreased from 95.7 % to 78.6 %. Thermal conductivity of these HEFCs varied from 1.87 W m- 1 K-1 to 1.60 W m- 1 K-1, which was lower than 8YSZ. As Ca2+ content increased, both size disorder and mass disorder increased too leading to low thermal conductivity. The results indicate that the prepared HEFCs are promising for thermal insulation applications.

A set of medium-/high-entropy pyrochlore oxides (M-HEPOs) with different compositions were designed and synthesized. The phase compositions of the prepared materials were determined through X-ray diffraction and Raman spectroscopy. Among the 24 designed samples, two high-entropy and six medium-entropy samples formed single-phase pyrochlore materials, two medium-entropy samples formed dual-phase pyrochlore materials, and the others formed multiphase materials dominated by the pyrochlore phase. The factors affecting the formation of single-phase pyrochlore structure were studied. The results revealed that size disorder is a major element determining the formation of single-phase pyrochlore, whereas mixing entropy has minimal effect. It is anticipated that this study will provide significant insights into the effects of size disorder and mixing entropy on the formation of M-HEPOs.

Since high-entropy oxide has a huge compositional space, it is urgent to develop efficient methods to quickly find the compositions that can form single-phase materials. In this paper, taking (Ce, Zr, Hf, Yb, Nb)O-2 system as an example, we carried out the design and preparation of high-entropy fluorite oxides (HEFOs) by constructing a R-S diagram. Three single-phase HEFOs have been successfully design and synthesized. The impedance measurement showed that the three materials are electronic conductors, which exhibited relatively low thermal conductivities ranging between 1.6 W/m center dot K similar to 1.9 W/m center dot K. The current study suggests that R -S diagram is a useful tool for quickly selecting compositions that can form single-phase high-entropy oxides.

Five equimolar multicomponent oxides were synthesized by replacing one of five cations in (Ce0.2Zr0.2Ti0.2Sn0.2Hf0.2)O2 with Ca2+. The results reveal that except for the one in which Ce4+ replaced by Ca2+, the other four components can form single-phase high-entropy fluorite oxides (HEFOs) at different temperatures, which indicates that Ce4+ is very important for the formation of single-phase HEFOs. The sintering behavior, lattice parameter and properties containing density, porosity, flexural strength and thermal conductivity of the four single-phase HEFOs were investigated. With the change of substituted ions, grain size, relative density, flexural strength and thermal conductivity of the materials vary greatly, which are correlated to the size disorder and mass disorder of these materials. The results of this paper provide a reference for the composition designing and performance tailoring of equimolar HEFOs.

To expand the utilization of iron tailings, four kinds of porous ceramics were prepared by foam gel-casting with pressureless sintering, foam gel-casting with reactive sintering, and mold forming with reactive sintering using fine-grained high-silicon iron tailings, iron tailings + graphite, and iron tailings + graphite + silicon carbide as raw materials, respectively. DSC-TG and XRD analysis was applied to investigate the sintering process of iron tailings and the carbothermal-reduction reaction between iron tailings and graphite. The four porous ceramics' porosities, compressive strengths, and thermal conductivities were further analyzed. The results show that the porous ceramics made only from iron tailings possesses high porosity (87.2%), compressive strength (1.37 MPa), and low thermal conductivity (0.036 W/(m.K)), meeting the requirement of thermal insulation material. Silicon carbide porous ceramics with improved thermal conductivity but a slight sacrifice of strength can be fabricated through carbothermal reduction between iron tailings and graphite. Moreover, the compressive strength of silicon carbide porous ceramics can be significantly increased by adding some silicon carbide to the raw materials. The silicon carbide porous ceramics achieved high porosity of 91.6%, high compressive strength of 1.19 MPa and thermal conductivity of 0.31 W/(m.K), which can be a guarantee of a carrier for composite phase change materials or light thermal conductive materials. Compared with foam gel-casting, the mold-forming process can significantly improve the thermal conductivity (1.15 W/(m.K)) of silicon carbide porous ceramics and greatly reduce the cost of raw materials and manufacturing, which is profitable for industrialization.

In this paper, we report the design and synthesis of La3+ based high-entropy pyrochlore ceramics (HEPCs) with five different B-site cations using the valence combination strategy. The factors affecting the formation of pyrochlore phase have been investigated. The result reveals that both valence disorder and size disorder can significantly affect the formability of pyrochlore phase, and the formability increases as the two disorders decrease. Following this guideline, a set of new HEPCs with single phase have been successfully synthesized.

High-entropy perovskite oxides with ferroelectricity have not been reported so far because these oxides have highly symmetric cubic structures. In this study, we propose a strategy of introducing morphotropic phase boundaries to obtain ferroelectricity in high-entropy perovskite oxides. We demonstrate the feasibility of the concept using (1−x)Pb(Mg0.2Zn0.2Nb0.2Ta0.2W0.2)O3–xPbTiO3 as a model system. It is anticipated that this concept can be applied to design and prepare various high-entropy ferroelectric and piezoelectric perovskite oxides.

In this paper, cordierite-based porous ceramics with magnetic properties have been firstly in-situ synthesized by using MgO, Al 2 O 3 , and SiO 2 powders as raw materials and Fe 3 O 4 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 Fe 3 O 4 . 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 °C due to the addition of Fe 3 O 4 . Except for the main phase-cordierite, Mg—Al—Fe spinel and α-Fe 2 O 3 also existed in the final materials. The lattice parameters of the Mg—Al—Fe spinel and the amount of α-Fe 2 O 3 changed obviously with the change in the sintering temperature and Fe 3 O 4 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.

High-entropy oxides (HEOs) are a new class of materials that are promising for a wide range of applications. Designing HEOs needs to consider both geometric compatibility and electrical equilibrium. However, there is currently no available method to systematically consider these two factors when selecting constituent materials for making HEOs. Here we propose a two-step strategy, where a HEO system to be explored is first partitioned into multiple subsystems based on the valence combinations of substituted cations; the geometric compatibility is then considered in selecting suitable substituted cations. We demonstrate this strategy by using A(5B0.2)O3 perovskite as a model system. We show that the system can be partitioned into 12 subsystems. Ten of the subsystems have formed a single-phase cubic perovskite, while two have partially ordering structure. The formation of single phases is correlated to Goldschmidt's tolerance factor, while the formation of the ordering structure is mainly correlated to cation-valence difference. We anticipate that this strategy is applicable to exploring HEOs in other systems.