Covalently bonded ceramics exhibit preeminent properties—including hardness, strength, chemical inertness, and resistance against heat and corrosion—yet their wider application is challenging because of their room-temperature brittleness. In contrast to the atoms in metals that can slide along slip planes to accommodate strains, the atoms in covalently bonded ceramics require bond breaking because of the strong and directional characteristics of covalent bonds. This eventually leads to catastrophic failure on loading. We present an approach for designing deformable covalently bonded silicon nitride (Si 3 N 4 ) ceramics that feature a dual-phase structure with coherent interfaces. Successive bond switching is realized at the coherent interfaces, which facilitates a stress-induced phase transformation and, eventually, generates plastic deformability.

Multifunctional phosphors have significant application and scientific value and are becoming a research hotspot in the field of luminescent materials. Herein, we report Mn 4+ -activated double-perovskite-type Sr 2 LuNbO 6 multifunctional phosphors with excellent comprehensive properties in the fields of optical temperature/pressure sensing and w-LED lighting. The crystalline structure, elemental composition, optimal doping concentration, crystal-field strength, and optical bandgap of the phosphors are investigated in detail, and the mechanisms of concentration and thermal quenching are discussed. From the optimal Sr 2 LuNb 0.998 O 6 :0.2%Mn 4+ phosphor, a LED lamp for indoor warm-white lighting is successfully fabricated. Further, the thermometric properties of the phosphors are explored for applications as FIR-and lifetime-based thermometers, showing a maximum relative sensitivity of 1.55% K −1 at 519 K. Upon pressure loading, a significant red-shift of the peak centroid is observed, and the pressure sensitivity is determined to be 0.82 nm/ GPa. These results suggest that the Mn 4+ -activated Sr 2 LuNbO 6 multifunctional phosphors have great potential to be utilized in the fields of optical thermometry, manometry, and lighting.

A novel deep‐red‐emitting phosphor Ca2ScNbO6:Mn4+ is prepared via a high‐temperature solid‐state reaction and its luminescent properties are systematically investigated. The results show that Mn4+‐activated Ca2ScNbO6 phosphors have broad absorption in ultraviolet region, and show bright deep‐red emission at 692 nm. The optimal doping concentration, crystal‐field strength, internal quantum efficiency, and mechanism of concentration and thermal quenching effects are discussed in detail. Moreover, NaF flux is screened out to improve both luminescent intensity and morphology of the phosphor. Finally, a red light‐emitting diode (LED) lamp is fabricated with as‐prepared Ca2ScNbO6:Mn4+ phosphors and a 365 nm LED chip. The electroluminescence spectra show a good overlapping with phytochrome PR and PFR absorbance. The results provided the as‐synthesized Ca2ScNbO6:Mn4+ phosphors a great potential in plant growth lighting.

Spherical Si@Si3N4 granules were first prepared by in situ combustion synthesis. The inside of the granules is dense without cracks, and the two phases at the interface are well‐bonded. More significantly, no binder was used between the Si3N4 grains on the surface layer, thereby avoiding phonons scattering of metal oxides. In addition, crystallographic orientation relationships between Si and Si3N4 were identified by coupling transmission electron microscopy with selected area electron diffraction technology, and much more potential matching planes are also predicted according to the edge‐to‐edge model. It was found that the minimization of the interfacial energy will promote the formation of a transition layer at the interface, leading to the well‐bonded between core and shell. On the basis of the observations, the underlying growth mechanism of the Si@Si3N4 was comprehensively analyzed and put forward. Benefiting from the remarkable merits, the as‐synthesized Si@Si3N4 granules showed great potential for alternative fillers in solving heat dissipation problems for electronic devices.

Si 3 N 4 powders were prepared by combustion synthesis with 1-and 3-μm α-Si 3 N 4 , β-Si 3 N 4 diluent and BN inert diluent. The maximum temperatures of samples with boron nitride (BN) as a diluent are about 1500-1600 • C lower than that of samples with α-Si 3 N 4 and β-Si 3 N 4 as diluents are about 1600-1800 • C. Moreover, the newly formed α-Si 3 N 4 contents in the synthesized products with BN as diluent over 90 wt% are much higher than those with α-Si 3 N 4 and β-Si 3 N 4 as diluent about 20-40 wt%. The strip-like α-Si 3 N 4 , rod-like β-Si 3 N 4 grains, and radiative shaped grains can be observed in the synthesized products. Finally, the effect of the diluent on the α-phase content of combustion synthesized Si 3 N 4 is discussed, which provides key guidance for preparing Si 3 N 4 powders with high α-phase content.