Oscillatory pressure sintering (OPS) technique was used to prepare silicon nitride ceramics with high quality. In comparison with hot pressure (HP) sintering process, the density, phase, grain size, aspect ratio and microstructure of silicon nitride ceramics by two methods were further investigated. The densification effect of oscillatory pressure on silicon nitride ceramics were studied. The results indicate that the silicon nitride ceramic has reached a complete phase transition from α phase to β phase under OPS process and its relative density has reached 99.82%. The grain sizes of OPS specimen are significantly increased compared with the specimen prepared by HP process. The average aspect ratio of the grains has increased from 3.79 to 4.86 when the fabricated process changed from HP to OPS. Bending strength, hardness and fracture toughness reached 1 333 MPa, 16.2 GPa, 12.1 MPa·m^1/2, respectively. Fracture surface energy also increased with the introduction of oscillatory pressure. In addition, obvious deformation streaks and dislocation movement areas are observed through TEM analysis. Obviously, the application of oscillatory pressure improves the densification rate and the growth driving force of grains. The plastic deformation of silicon nitride during the densification process were also found. Thereby, the sintering densification process was accelerated.

Aerogels are known as the "magic material to change the world in twenty-first century". Because of its unique super porous structure, it has many excellent properties and wide application prospect in many fields. However, the mechanical brittleness and the cumbersome preparation process caused by the network structure of aerogels greatly hamper its widely application, which is a bottleneck problem in the aerogel field. The development status of aerogel materials is reviewed, and several structural strengthening strategies commonly used in aerogels are summarized. The classification and preparation of aerogels and the strategies for optimizing the structure and properties of aerogels are summarized. At the same time, the methods of optimization and enhancement in recent years such as biomimetic reinforcement, concentration induced hardening and microwave sintering are reviewed. Meanwhile, the prospect of aerogel is also forecasted.

The fracture toughness of zirconia toughened alumina (ZTA, 15% ZrO₂ in mass fraction) ceramics was improved via the addition of plate-like Pr_0.833Al_11.833O₁₉ crystals prepared by in-situ solid-state reaction. The effects of Pr₆O₁₁ dopant content and sintering system on the microstructure and mechanical properties of ZTA ceramics were investigated. The results show that the plate-like Pr_0.833Al_11.833O₁₉ crystals can be in-situ prepared at Pr₆O₁₁ doping content of >1.0% (mass fraction) and by heat preservation at 600℃ for 4 h, 800℃ for 1 h and 1 600℃ for 2 h, respectively. The ZTA ceramic with the plate-like crystals at an average aspect ratio of 11.76 uniformly distribute at Al₂O₃ grain boundary has the fracture toughness of 6.37 MPa·m^1/2, which is increased by 88%, compared to the ZTA ceramic without the plate-like crystals.

The secondary pressure assisted flash sintering process of tetragonal zirconia ceramics was developed. The process optimized the process and eliminated the deterioration of microstructure caused by high power flash sintering at critical flash temperature. The results show that: the multi-step pressure assisted flash sintering process retains the advantages of low-temperature and instantaneous sintering, avoids the complex green pressing process and the high cost of precious metal electrode. Yttrium stabilized zirconia can be densified by multiple flash sintering. The sintering temperature is lower than 1 050℃ and the sintering time is less than 200 s. The density of tetragonal zirconia ceramic material prepared by this process is more than 90%.

White light emitting diode (WLED) is considered as a fourth-generation green light source and presents some applications in lighting fields due to its advantages of long service life, high luminous efficiency, and free environmental pollution. The exisiting main commercialization use of WLED is a blue chip combined with YAG:Ce³⁺ phosphor. However, the luminescence performance of the WLED gradually declines with the increase of temperature due to a poor thermal conductivity of the resin encapsulating the phosphor, thus becoming difficult to apply to high-power lighting. It is necessary to obtain the superior phosphor materials with high quality and stability. In recent years, directionally solidified Al₂O₃/YAG:Ce³⁺ eutectic phosphor composite is considered as a novel bulk phosphor material for a high-power WLED lighting, which is expected to substitute conventional phosphors, due to its excellent luminous properties, high temperature strength and thermal stability, low power consumption as well as superior quantum efficiency. This review summarized the main preparation technologies of Al₂O₃/YAG:Ce³⁺ eutectic phosphor composite. Meanwhile, the microstructure, luminescence mechanism, and influential factors of the Al₂O₃/YAG:Ce³⁺ eutectic phosphor composite were analyzed. In addition, the future development direction was also discussed.

Based on the introduction of the dislocation formation and movement mechanism in Czochralski silicon, the effects of seed crystal thermal shock, solid-liquid interface, crystal diameter, and impurities on the dislocations during the crystal growth process were summarized. The effects of boron, germanium, nitrogen, phosphorus, arsenic doping elements and oxygen impurities on the dislocation behavior of the Czochralski silicon were analyzed. The thermal shock of the seed crystal can lead to the dislocations, which can be suppressed by some methods such as necking, melting back, seed crystal preheating, and the use of doped seed crystal. The solid-liquid interface convex to the melt causes a large edge shear stress to produce the edge dislocations. The formation of dislocations can be suppressed when the shape is flat. In heavily n-type doped single crystal silicon, the evolution of solid-liquid interface and the formation of {111} edge surface may promote the generation of supercooling region and interrupt the growth of top cone, thereby causing the dislocations, and the length of the edge surface is related to the curvature of the melting isotherm. Incomplete seeding of the seed crystal will produce the dislocations that cannot be discharged from the crystal, and then extend to the silicon rod. The increase in the diameter of single crystal silicon and the fluctuation of the diameter during the crystal growth process will increase the risk of dislocation formation. Doping is an effective method to inhibit the formation and movement of dislocations. Boron, germanium, nitrogen, phosphorus, arsenic and oxygen impurities all have different degrees of inhibition on the dislocations mainly due to the pinning effect of impurity atoms on the dislocations. Finally, some future research aspects on necking process, thermal field design, doping process and theoretical modeling were prospected.

The micropipe (MP) in silicon carbide (SiC) single crystal substrate is a fatal defect for SiC-based devices, which will seriously affect the yield of SiC power devices. In this paper, the 6 in n-type 4H-SiC single crystals without micropipe defect were prepared by the optimized growth design based on physical vapor transport (PVT) method. The effects of the optimized growth design on the elimination of micropipes were also studied. Based on the principle of crystallography and kinetics, the mechanism of micropipe decomposition and closing is clarified. In summary, the optimized growth design adopted in this paper not only promotes the stability of SiC single crystal growth, but also can improve the crystalline quality of SiC single crystal, and can quickly reduce the density of micropipes. The prepared large size 6 in n-type 4H-SiC single crystals without micropipe defect will be more suitable for making high-voltage and ultra-high-voltage power devices.

After the optimization of temperature field and the process parameters, the NaCl single crystal with the size ofФ130 mm×100 mm was grown by the resistance heating Czochralski (Cz) method and the bottom of the crucible compensation technology. XRD analysis shows that the NaCl crystal is a cubic system with a lattice constant of a=0.564 02 nm. The transmittance test of the crystal suggests that the transmittance of a sample with a thickness of 4 mm is greater than 91.5%. The vickers hardness of the crystal is 21.52 kg/mm², and the hardness coefficient is 1.672, which proves that NaCl crystal is a soft material. The optical uniformity of the crystal decreases with the dislocation density increase. The thermoluminescence luminescence (TL) curve shows that the thermoluminescence peaks of the crystal are located at 74.35 and 221.14℃, respectively, and the luminous intensity of the latter is more than 5 times that of the former. The results show that NaCl crystal is a high-quality material, which can be used in dosimetry and infrared fields.

A series of Cs₂NaBiCl₆:Mn²⁺ double perovskite phosphors were prepared via liquid-phase synthesis, and their structures and luminescent properties were investigated by X-ray diffraction and fluorescence spectroscopy. The result show that with the gradual introduction of Mn²⁺, localized excitations centered on Bi³⁺ ions in the host lattice Cs₂NaBiCl₆ strongly absorb near-UV light, and the energy transfer between Bi³⁺ and Mn²⁺ promotes the electron transition between atomic d orbitals, thus leading to an intense orange-yellow photoluminescence. The photoluminescence reduces when the manganese-bismuth molar ratio is 0.7 due to the concentration quenching effect. Also, a broad emission peak centered at 590 nm is assigned to the ⁴T₁→⁶A₁ transition of octahedrally coordinated Mn²⁺. Based on the excitation spectrum, there are some peaks at 354 nm that arise from 6s²→6s¹6p¹ excitations of Bi³+ions. It is indicated that Cs₂NaBiCl₆:Mn²⁺ could be a promising fluorescent phosphor synthesized without the use of expensive reagents and toxic elements materials.

Tb³⁺ single doped and Tb³⁺/Ce³⁺ co-doped high aluminum blast furnace slag, aluminosilicate luminescent glass was prepared by a high-temperature water-quenching method. The effects of heat treatment and co-doping on the luminous properties of glass were studied. The results show that, after holding at 1 000℃ for 4 h, the glass host crystallizes into Ca₂(Mg_0.5Al_0.5)(Si_1.5Al_0.5O₇), and the luminescence performance drops sharply. The highest luminous intensity of 4%(mole fraction) Tb³⁺ doped luminous glass is about 12 times higher than of that crystallized. With Ce³⁺ ions introduced, energy transfer occurs between Ce³⁺ ions and Tb³⁺ ions due to multipolar interaction, and the luminous intensity of Tb³⁺/Ce³⁺ co-doped luminescent glass reaches nearly 6 times of the Tb³⁺ single doped. 4%Tb³⁺/1%Ce³⁺ co-doped luminescent glass has good luminescence thermal stability at 150℃, and can be used as a green solid-state luminescent material excited by near ultraviolet LED.