Spinel-Based ZnAl2O4: 0.5%Cr3+ Red Phosphor Ceramics for WLED

To address the issue of the lack of red light in traditional Ce3+: YAG-encapsulated blue LED white light systems, we utilized spark plasma sintering (SPS) to prepare spinel-based Cr3+-doped red phosphor ceramics. Through phase and spectral analysis, the SPS-sintered ZnAl2O4: 0.5%Cr3+ phosphor ceramic exhibits good density, and Cr3+ is incorporated into [AlO6] octahedra as a red emitting center. We analyzed the reasons behind the narrow-band emission and millisecond-level lifetime of ZAO: 0.5%Cr3+, attributing it to the four-quadrupole interaction mechanism as determined through concentration quenching modeling. Additionally, we evaluated the thermal conductivity and thermal quenching performance of the ceramic. The weak electron-phonon coupling (EPC) effects and emission from antisite defects at 699 nm provide positive assistance in thermal quenching. At a high temperature of 150 °C, the thermal conductivity reaches up to 14 W·m−1·K−1, and the 687 nm PL intensity is maintained at around 70% of room temperature. Furthermore, the internal quantum efficiency (IQE) of ZAO: 0.5%Cr3+ phosphor ceramic can reach 78%. When encapsulated with Ce3+: YAG for a 450 nm blue LED, it compensates for the lack of red light, adjusts the color temperature, and improves the color rendering index (R9). This provides valuable insights for the study of white light emitting diodes (WLEDs)

Mechanism of Surface Defects in Ultra-Precision Machining of Sesquioxide Laser Crystal Tm: GdScO3

It is well-known that the surface quality of laser gain crystal elements is very high in order to ensure the stability of laser system and laser output quality. In the ultra-precision machining process of a new sesquioxide laser crystal Tm: GdScO3, it is required to achieve very high surface shape and very low surface defects. In this paper, the molecular dynamics simulation model of single particle grinding was established. It was found that the normal load and tangential friction imposed by abrasive particles on the surface of components cause the spalling of atoms on the substrate surface, which constitutes the removal of materials at the macro-level. At the same time, it causes the displacement of the sub surface atoms, which constitutes the microscopic defects in the structure. Through the structural characterization of macro defects, it was confirmed that the essence of micro defects is the amorphous and distortion of surface structure, and the depth can reach 100 nm. The results of lapping and polishing experiments show that the adjustment of pressure has a limited effect on the improvement of surface defects in the process of machining crystal elements with granular abrasive

CHEMICAL MECHANICAL POLISHING AND ITS MECHANISM ON YTTERBIUM-DOPED MIXED SESQUIOXIDES (Yb:LuScO₃)

In this paper, Yb:LuScO3 crystal was processed by chemical mechanical polishing (CMP), and the surface roughness of 0.18[Formula: see text]nm was obtained. The atomic step structures of these sesquioxide crystals are successfully characterized by AFM scanning probe technology. Through several CMP experiments, the basic material removal mechanism of a ytterbium-doped LuScO3 crystal during CMP is studied. Based on the findings, a material removal model is established. The results of this study provide ideas for the study of CMP, crystal growth and epitaxy. </jats:p

Numerical simulation of pitch button blocking optimization

An ideal pitch button blocking process determines the level of workpiece deformation, especially the high-aspect-ratio optics, during the blocking process and process of polishing later. We have studied the pitch button blocking process by Finite Element Analysis (FEA) according to the thermoelastic equation. Meanwhile, the optimized pitch button blocking has been gotten by FEA which includes the thickness and material of blocking plate, as well as the radius, arrangement, elastic modulus and coefficient of thermal expansion of pitch buttons. The numerical simulation of Nd: glass (empty set100 mmx2 mm thickness) shows that the surface figure change (Delta PV) which is induced by the thermal stress during pitch button blocking process is influenced seriously by the thickness of blocking plate