Single crystal diamond (SCD) possesses excellent mechanical, thermal, photoelectric properties and thus has important application values in aerospace, optoelectronics, high-power electronic devices and quantum technology. Microwave plasma chemical vapor deposition (MPCVD) is the mainstream technique for synthesizing high-quality single crystal diamond. Nevertheless, it is restricted by seed crystal size, as well as the problems of stress accumulation, defect propagation and deteriorated growth during large-area growth, which makes it difficult to realize the large-scale fabrication of inch-sized high-quality single crystal diamond. The mosaic splicing method achieves interfacial fusion via lateral epitaxial growth of multiple seeds, effectively breaking the size limitation of a single seed crystal and offering a new technical route for the preparation of large-size single crystal diamond. This paper reviews the research progress of preparing large-size and high-quality single crystal diamond by the mosaic splicing method in recent years. It mainly analyzes the formation mechanism of defects and the evolution law of stress at splicing interfaces, as well as the influence of step flow regulation on interfacial bonding quality. Key technologies including equipment optimization, seed pretreatment, interfacial regulation and growth parameter optimization are summarized. On this basis, future research priorities are proposed: developing technologies for high-precision crystal orientation matching and atomic-level interfacial reconstruction, exploring low-damage and reusable lift-off processes, establishing the synergistic regulation mechanism of temperature field, flow field and plasma field during large-area growth, and constructing in-situ monitoring and multi-scale characterization techniques. The above research aims to reduce the defect density at splicing interfaces, precisely control residual stress and improve growth uniformity, so as to provide theoretical basis and technical support for the industrial production of inch-sized high-quality single crystal diamond wafers.

Ceramic materials have obvious advantages in thermal stability, but impedance mismatch limits their ability to attenuate electromagnetic (EM) waves. Herein, a novel series of high-entropy (V_0.2Nb_0.2Zr_0.2Ta_0.2X_0.2)B₂ (X = Mo, Ti, and Hf) ceramics were successfully synthesized via ultrafast high-temperature sintering (UHS) apparatus based on joule heating. The results indicated that the effect of high-entropy component on the magnetic loss of the system was relatively small, but the effect on the dielectric loss was larger. Among them, the (V_0.2Nb_0.2Zr_0.2Ta_0.2Ti_0.2)B₂ (HEB-Ti) sample demonstrated superior absorbing properties due to relatively moderate dielectric loss and optimal EM impedance matching. Moreover, because of its relatively moderate attenuation constant, it could achieve the maximum penetration of the EM wave and the minimum reflection after absorbing wave. As a result, the minimum reflection loss (RL_min) was as low as −40.7 dB, and the effective absorption band covered the entire low-frequency range from 2 to 8 GHz. Its excellent absorption performance was mainly due to the synergistic effect of various dielectric attenuation mechanisms, including defect polarization, dipole polarization, and conduction loss. Furthermore, thermogravimetric (TG) analysis showed that the sample exhibited excellent thermal stability and could withstand temperatures up to 550 °C in air and 1000 °C in an argon gas environment. The relevant work could provide meaningful references for the design of new high-performance ceramic wave-absorbing materials.