The exploration of transition metal Mn²⁺-activated luminescent materials is gaining increasing interests due to their diverse uses. Herein, Mn²⁺-incorporated fluorphlogopite (FP; KMg₃AlSi₃O₁₀F₂) mica ceramics were successfully prepared by a high-temperature solid-state reaction process, in which Mn²⁺ occupied the Mg²⁺ site through isomorphic substitution. The FP itself and derived Mn-mica (KMg_2.5Mn_0.5AlSi₃O₁₀F₂) possess negligible luminescence under ultraviolet (UV) excitation. However, the doping of rare earth Eu²⁺ into Mn-mica generates an evident deep-far-red broadband emission at approximately 620–860 nm, peaking at 720 nm when excited with 240–360 nm, which is ascribed to the intrinsic ⁴T₁ → ⁶A₁ transition of Mn²⁺, and the maximum spectral enhancement reaches approximately 22-fold when excited with 320 nm. The more dramatic result is that the complete substitution of Na⁺ for K⁺ in Mn-mica (NaMg_2.5Mn_0.5AlSi₃O₁₀F₂) not only results in an enlarged excitation range toward the near-UV region but also greatly enhances the deep-far-red emission (more than 12-fold) under 365 nm excitation. After optimization, the luminescence internal quantum yield (QY) is 87.4%, and the emission intensity at 423 K retains 78% of that at ambient temperature, indicating that the modified mica ceramics have superior luminescence and thermal stability through the cooperative effects of isomorphic cation substitution and doping, which is applicable for plant cultivation lighting and latent fingerprint identification.

In the upcoming 6-generation (6G) revolution, the achievement of low power consumption has become a key objective in research concerning terahertz devices. As an important component of passive devices, there are very few low-loss dielectric ceramics in the terahertz range. To elucidate the mechanism of loss and promote the application of microwave dielectric ceramics for future 6G technology (covering microwave and terahertz frequencies), the terahertz responses of ANb₂O₆ (A = Zn, Co, Mn, and Ni) columbite niobates were studied. The influences of magnetic loss on the Q×f values in the microwave range with different transition metal ions in the A-site were reasonably analyzed. Moreover, due to the weakened magnetic relaxation properties in the terahertz range, the samples all exhibited low loss and approximate transparency, especially for MnNb₂O₆ and NiNb₂O₆ (tanδ < 0.01 and absorption coefficient < 10 cm⁻¹ below 1.2 THz), which subverted the definition of traditional low-loss microwave dielectric ceramics. Ultimately, based on Mie theory, we designed a prototypical broadband metamaterial reflector to validate the applicability of the ANb₂O₆ system in the terahertz band, which is highly important for the development of terahertz ceramic-based passive devices.

Metadevices have emerged as a new element or system in recent years, from optics to mechanical science, showing superior performance and powerful application potential. In this study, a mechanical metadevice that capable of low-frequency vibration isolation, which is called metamaterial springs or metasprings, is proposed. Meanwhile, a modular design method is reported to obtain the customizable quasi-zero stiffness characteristic of the designed metaspring. As proof-of-concept, we demonstrate, both in simulations and experiments, the quasi-zero stiffness characteristics of the proposed metasprings using 3D-printed experimental specimens. Moreover, the low-frequency vibration isolation properties of the proposed metasprings is demonstrated both in vibration tests and automotive vibration tests. This work provides a new mechanical metadevice, that is, metasprings for low-frequency vibration isolation, as well as a modular design method for designing metasprings, which may revolutionize vibration isolation devices in the field of low-frequency vibration isolation.

It is possible to improve the machinability of aluminum nitride-hexagonal boron nitride (AlN-h-BN) ceramics while maintaining high strength and high thermal conductivity. The composite ceramics with 0-30 wt% BN as secondary phase were prepared by hot pressed sintering, using yttrium oxide (Y₂O₃) as sintering aid. The phase composition, density, microstructure, mechanical properties, thermal conductivity, and dielectric properties were investigated. The sintering additives were favorable to purify the grain boundaries and improve densification, reacting with oxide impurities on the surface of raw material powder particles. The optimum BN content improved the flexural strength and fracture toughness of composite ceramics with 475 MPa and 4.86 MPa·m^1/2, respectively. With increasing the amount of BN, the thermal conductivity and hardness of composites gradually decreased, but the minimum value of thermal conductivity was still 85.6 W·m^-1·K^-1. The relative dielectric constant and dielectric loss tangent of the samples ranged from 6.8 to 8.3 and from 2.4 × 10^-3 to 6.4 × 10^-3, respectively, in 22-26 GHz.

High performance low temperature co-fired ceramic (LTCC) dielectrics is highly desired for next generation information technology. The rational design is a key issue for the development of new LTCC materials. In comparison to the design of conventional electroceramics, more attention should be paid on the formation process of the material structure for that of LTCC, in addition to the physical properties, due to the special requirement in fabrication processing. In this paper, sintering mechanism of three types of LTCC materials, i.e., glass-ceramics, glass ceramic composite, and glass bonded ceramics, as well as important factors of their dielectric properties are discussed and summarized, and the design strategies for LTCC dielectrics, based on new matrix materials with much lower sintering temperature or higher quality, are proposed. As an example for rational design, oxyfluoride glass-ceramic based dielectrics, a new class of LTCC materials with low ε_r, is analyzed.