High-entropy ceramics (HECs), defined as single-phase inorganic solid solutions comprising five or more principal elements in equimolar or near-equimolar ratios, have emerged as a frontier and hotspot in materials science over the past decade. Their expansive compositional space and diverse crystal structures open up new avenues for the design and performance regulation of ceramic materials. Initially, focused on proving the feasibility of entropy-stabilized phases, the field rapidly expanded into a vast, complex landscape of nonequimolar, multianionic, and medium-entropy compositions. This exploratory "great chaos" successfully validated the concept across diverse ceramic families and unlocked extraordinary properties, including ultrahigh temperature stability, exceptional radiation tolerance, ultralow thermal conductivity, and superior energy storage density. The realization of performance-tailored HECs fundamentally depends on rational compositional design and precise control of preparation processes, core challenges that remain at the heart of current research. However, a clear "scissors gap" has emerged between the rapid accumulation of experimental data and the lag in theoretical frameworks and data comparability. This review synthesizes a decade of research to chart a crucial transition "from chaos to order". It formulates emerging design paradigms for targeted applications such as oxidation-resistant ultrahigh temperature ceramics (UHTCs), thermal barrier coatings, durable nuclear materials, and high-performance energy storage and conversion materials. The analysis highlights the shift from discovery to quantitative efforts integrating computational thermodynamics, advanced characterization, and machine learning (ML). Despite remarkable progress, significant bottlenecks persist in processing, standardized characterization, and scaling from powder to component. The future roadmap emphasizes establishing robust structure–property relationships, fostering community-wide data standards, and advancing rational, physics-, and artificial intelligence (AI)-guided design to systematically realize the immense technological potential of HECs.

With the development of aerospace technology, the Mach number of aircraft continues to increase, which puts forward higher performance requirements for high-temperature wave-transparent materials. Silicon nitrides have excellent mechanical properties, high-temperature stability, and oxidation resistance, but their brittleness and high dielectric constant impede their practical applications. Herein, by employing a template-assisted precursor pyrolysis method, we prepared a class of Si₃N₄@SiO₂ nanowire aerogels (Si₃N₄@SiO₂ NWAGs) that are assembled by Si₃N₄@SiO₂ nanowires with diameters ranging from 386 to 631 nm. Si₃N₄@SiO₂ NWAGs have low density of 12–31 mg∙cm⁻³, specific surface area of 4.13 m²∙g⁻¹, and average pore size of 68.9 μm. Mechanical properties characterization shows that the aerogels exhibit reversible compressibility from 60% compressive strain and good fatigue resistance even when being compressed 100 times at set strain of 20%. The aerogels also show good thermal insulation performance (0.032 W·m⁻¹∙K⁻¹ at room temperature), ablation resistance (butane blow torch), and high-temperature stability (maximum service temperature in air over 1200 ℃). The dielectric constant and loss of the aerogels are 1.02–1.06 and 4.3×10⁻⁵–1.4×10⁻³ at room temperature, respectively. The combination of good mechanical, thermal, and dielectric properties makes Si₃N₄@SiO₂ NWAGs promising ultralight wave-transparent and thermally insulating materials for applications at high temperatures.

SiC ceramics are attractive electromagnetic (EM) absorption materials for the application in harsh environment because of their low density, good dielectric tunable performance, and chemical stability. However, the performance of current SiC-based materials to absorb EM wave is generally unsatisfactory due to poor impedance matching. Herein, we report ultralight SiC/Si₃N₄ composite aerogels (~15 mg·cm⁻³) consisting of numerous interweaving SiC nanowires and Si₃N₄ nanoribbons. Aerogels were prepared via siloxane pyrolysis and chemical vapor reaction through the template method. The optimal aerogel exhibits excellent EM wave absorption properties with a strong reflection loss (RL, −48.6 dB) and a wide effective absorption band (EAB, 7.4 GHz) at a thickness of 2 mm, attributed to good impedance matching and multi attenuation mechanisms of waves within the unique network structure. In addition, the aerogel exhibits high thermal stability in air until 1000 ℃ and excellent thermal insulation performance (0.030 W·m⁻¹·K⁻¹). These superior performances make the SiC/Si₃N₄ composite aerogel promising to become a new generation of absorption material served under extreme conditions.