Lanthanide metal-organic framework (Ln-MOF) is a novel inorganic-organic porous material, which is composed of organic ligands and lanthanide metal ions or metal clusters. Ln-MOFs have abundant molecular building blocks and a high fluorescence quantum efficiency due to the high coordination number and unique optical properties of lanthanide metal ions. This review summarized recent work on Ln-MOFs, mainly focusing on the application of Ln-MOFs in photonics such as temperature detection, small molecule detection, gas detection, etc. The design and controllable preparation methods of Ln-MOFs as well as the assembly of organic dyes, perovskite quantum dots, etc. in the Ln-MOFs channel and the assembly of Ln³⁺ in the MOFs channel were introduced. In addition, the future development and application prospects of the Ln-MOFs were also proposed.

Photodetection technology is widely used, especially near-infrared (NIR) photodetector plays an essential role in military, communication and industrial automation. With the development of semiconductor laser technology, multiband photodetectors (PDs) have great application prospects in imaging technology, environmental monitoring, medical detection, optical communication, and flexible equipment. The selective PDs of the NIR Ⅰ-Ⅱ region with a low pump threshold and a high sensitivity is investigated for developing polychromatic bioimaging/sensor encrypted communication in bioanalysis. Recent work on the NIR selective PDs mainly focus on integrating infrared semiconductor materials with different band gaps and NIR response capabilities as well as increasing the complexity and stability of the device design and cost. Rare-earth ions (RE³⁺) doped upconversion nanocrystals (UCNCs) can absorb the NIR photons and convert them into UV or Vis photons, then being absorbed by semiconductors with a wide band gap. The UCNCs have a large Stokes/anti-Stokes shift, a superior photostability, and a selective absorption at NIR wavelengths, thus considering as good narrowband NIR photoactive materials with a potential strategy for developing the new generation of NIR selective PDs. In UCNCs-based PDs, coupling with perovskite, graphene, or MoS₂ enables the PDs to exhibit an excellent responsivity and achieve a wide spectral range that a single component cannot achieve. However, UCNCs-based PDs have some problems of low fluorescence efficiency and high pump threshold of UCNCs in practical application. This review summarized recent research on utilizing RE³⁺-doped UCNCs as photoactive materials for NIR PDs, and represented several primary strategies for enhancing UCL efficiency/intensity to achieve narrowband NIR PDs. Meanwhile, the advancement of combining UCNCs with perovskite, graphene, and MoS₂ for the NIR PDs was described. In addition, recent work on RE³⁺-doped UC-perovskite NIR PDs was also given.

The electricaloric refrigeration is based on the electricaloric effect due to its high energy conversion efficiency, environment friendly, small size and easy integration as a novel efficient refrigeration technology, which has become one of the emerging research hotspots in the field of ferroelectric. The solid solutions of 0.77NaNbO₃-0.23BaTiO₃+wMn (w=0, 0.2%, 0.4% and 0.6%, in mass fraction) electrocaloric ceramics were prepared by a conventional solid-state reaction method. The phase composition and microstructure of 0.77NaNbO₃-0.23BaTiO₃ ceramics with different Mn doping contents were characterized by X-ray diffraction and scanning electron microscopy. Meanwhile, the dielectric-temperature spectra, polarization electric field hysteresis loops and electrocaloric effect of the samples with different Mn doping contents were determined. The results indicate that Mn doped ceramics can promote the grain compaction, improve the dielectric constant and saturation polarization strength, reduce the dielectric loss, and enhance the electrocaloric effect. For the ceramic with Mn doping content w of 0.4%, ΔT=0.39 K, and ΔS=0.71 J·kg^-1·K^-1, the electrocaloric strength of ΔT/ΔE enhances from 0.05×10^-6 K·m·V^-1 to 0.13×10^-6 K·m·V^-1, and ΔS/ΔE enhances from 0.08×10^-6 K m·V^-1 to 0.24×10^-6 J·m·kg^-1·K^-1·V^-1 under 30 kV·cm^-1 at room temperature. It is indicated that 0.77NaNbO₃-0.23BaTiO₃+0.4%Mn ceramic could be used as an promising electrocaloric refrigeration material.

The ZnO-Pr₆O₁₁-Co₂O₃-Cr₂O₃-Er₂O₃-SiO₂ varistors were prepared by a solid-state sintering method. The effect of SiO₂ doping on the phase, microstructure, varistor property, and impedance characteristic of the ZnO varistors was investigated. The results show that the grain size decreases gradually with the increase of SiO₂ content due to the restraining effect of grain growth in SiO₂. The ZnO varistor with SiO₂ content of 1.0% (in mole fraction) has an optimum overall performance to provide overvoltage protection for circuit (i.e., the most second phase generated, the maximum breakdown voltage of 435.5 V/mm, the maximum mean grain boundary voltage of 1.63 V, the maximum nonlinear coefficient of 17.5, and the maximum resistivity of grain boundary of 17 400 MΩ·cm, the maximum barrier height of grain boundary of 0.37 eV, and the minimum leak current of 1 μA, respectively). The breakdown voltage and nonlinear coefficient of ZnO varistor with SiO₂ content of 1.0% are 3.6 and 6.6 times greater than those of ZnO varistor without SiO₂.

Ti(C,N)-WC-Al₂O₃/Ti(C,N)-WC laminated ceramic materials with different layers and layer thickness ratios were prepared via microwave sintering. The variation of residual stress with layer number and layer thickness ratio was revealed by a finite element method, and the effects of layer number and layer thickness ratio on the macro-mechanical properties and micro-structural characteristics of the material were investigated. The results show that compared with the homogeneous material, the fracture toughness of the laminated material increases to 11.42 MPa·m^1/2, which is 2.5 times greater than that of the homogeneous material, indicating a superior toughening effect. The main reason is a combined effect of macroscopic residual compressive stress and massive microscopic crack deflections. The fracture mode of the laminated material is an effective mixed fracture mode. In such a mode, the transgranular fracture of the surface layer and the intergranular fracture of the matrix layer alternate, which is conducive to the increase of fracture toughness and to the improvement of the overall strength of the material.

High quality ceramic targets is crucial to produce BaBiO₃-based negative temperature coefficient (NTC) thermosensitive films via RF magnetron sputtering. In this paper, the shrinkage, flatness and volume density of pure BaBiO₃ target were measured, and the orthogonal experiment was designed via changing the major factors (i.e., compressive time, sintering temperature, holding time and heating rate), and the structure-activity relationship between each factor and the target material quality index was analyzed. Also, based on the influence of sintering behaviors on the grain growth of BaBiO₃ ceramic targets, the key sintering process factors such as sintering temperature, holding time and heating rate were regulated by the phenomenological equation and intercept method to discuss the intrinsic relationship among the grain growth mechanism, growth index n and key influencing factors. According to the results by X-ray diffraction, Raman spectroscopy and scanning electron microscopy-enery dispersive spectroscopy, the phase structure and elemental composition of the target samples obtained at the given process factors were analyzed. The results show that BaBiO₃ ceramic targets with slight deformation, high density and good apparent quality can be obtained under the optimum conditions (i.e., compressive time of 12 min, sintering temperature of 750 ℃, holding time of 120 min and heating rate of 2 ℃/min).

MgAl₂O₄ transparent ceramic is a superior mid-infrared material, which is widely used in military and civil fields. In this paper, the effect of sintering process on the phase, microstructure and optical properties of magnesia alumina spinel transparent ceramics was investigated, and the sintering process route suitable for high-quality magnesia alumina spinel transparent ceramics was determined, which is of great significance for accelerating the industrialization of large-scale transparent ceramic armor materials. The results show that Li ions in hot pressed (HP) MgAl₂O₄ transparent ceramics may exist in the form of LiAlO₂. The preferential growth surface of MgAl₂O₄ transparent ceramics obtained by hot isostatic pressing (HIP) sintering process is (311). Al and Mg ions of MgAl₂O₄ ceramics prepared by HP and HIP sintering deviate from the stoichiometric ratio, and Al/Mg ratio is greater than 2. The small grains in the ceramics increase with the increase of HIP pressure, and the grain size of MgAl₂O₄ ceramics is within 20-40 μm, which is conducive to improving the average transmittance of 3-5 μm. Based on the results by hot isostatic pressing test, the HIP sintering temperature of 1 750 ℃ and the pressure of 170 MPa are conducive to improving the average infrared transmittance (>85 %). In addition, the HIP sintering time has little effect on improving the infrared transmittance of MgAl₂O₄ transparent ceramics.

Sialon ceramic tool materials were prepared by a microwave sintering technology. The influences of sintering temperature and holding time on the mechanical properties of Sialon ceramic tool materials were investigated, and the microstructure was analyzed. The results show that the tool material obtained at the sintering temperature of 1 600 ℃ and the holding time of 15 min has the optimum mechanical properties (i.e., density of 98.9%, hardness of 17.8 GPa and fracture toughness of 5.9 MPa·m^1/2, respectively). In this sintering process, the material has a uniform microstructure with little internal pores, which is conducive to the improvement of its mechanical properties. The ceramic tool material with the superior mechanical properties can be obtained for a short time of heat preservation as the microwave sintering technology is used, thus improving the production efficiency.

A joint of SiCBN ceramic and Ti₂AlNB alloy was prepared via transient liquid phase diffusion bonding with AgCu fillers. The effects of joining temperature and holding time on the microstructure and mechanical properties of the joint were investigated. In joining, Ti dissolves from Ti₂AlNb alloy into Ag—Cu melt and reacts with SiBCN ceramic to form a continuous TiC interfacial layer, while Cu in the liquid phase diffuses towards Ti₂AlNb alloy to produce Nb(s, s) and TiCu₂Al, resulting in the isothermal solidification of melts. A thicken TiC layer appears, Cu(s, s) vanishes and the fraction of TiCu₂Al compound increases as the joining temperature or holding time increases. The shear strength at room temperature firstly increases and then decreases as the joining temperature or holding time increases. The joint prepared at 840 ℃ for 40·min exhibits a maximum shear strength of (73±10) MPa and (95±16) MPa at room temperature and 500 ℃, respectively, which is mainly attributed to the good stress-relief ability and thermal resistance of Ag(s, s).

A porcelain was prepared with Kaolin clay, potassium feldspar and quartz as raw materials and zirconium silicate as a reinforcing material. The effects of zirconium silicate content, firing temperature and holding time on the properties of porcelain were investigated, and the strengthening mechanism of zirconium silicate particle dispersion on the porcelain was analyzed. The results show that the optimum porcelain reinforcement can be obtained at zirconium silicate content of 6%, firing temperature of 1 300 ℃ and holding time of 30 min. The bending strength increases from (58±6) MPa to (106±11) MPa, and the growth rate is 83%. The radial compressive stress and tangential tensile stress are generated in the matrix during the cooling process due to the difference of thermal expansion coefficient between zirconium silicate particles and matrix, resulting in the increased porcelain strength.