Benxue Jiang

Mg2+ - codoped Gd2YAl2.4Ga2.6O12:Ce ceramic scintillator was fabricated by sintering in an oxygen atmosphere and hot isostatic pressing. It exhibits a high integral scintillation efficiency of 400 % of Bi4Ge3O12 crystal scintillator. Under excitation with 662 keV γ rays, it shows a light yield value of 22,200 photons/MeV along with scintillation decay times of 24.5 ns (24%) + 75 ns (76%). The scintillation response under excitation with 5.5 MeV α particles from a 238Pu source was also investigated and discussed.

Transition‐metal Mn ²⁺ ion‐doped transparent ceramics (TCs) are promising color‐convertors to improve color rendition for solid‐state lighting. However, the stabilization of Mn ²⁺ remains a challenge owing to the changeable atmosphere in the specific preparation of TC. In this work, the variations of valence states of Mn ions in typical garnet lattice host (YAG and LuAG) throughout the TC fabrication were demonstrated. By combined first principles calculation and experimental investigation, an enhanced self‐reduction of Mn ions was clarified in LuAG host, which was originated from the higher concentration of oxygen vacancy defects. Moreover, the air annealing treatment could significantly weaken and enhance the absorption of Mn ²⁺ and Mn ³⁺ respectively, degrading the orange–red emission peaking at 594 nm. On account of the oxidation of Mn ²⁺ ions, a photoluminescence spectra redshift of 9 nm was observed with increasing air annealing temperature and oxygen content, owing to strengthened crystal field strength surrounding Mn ²⁺ ions. Finally, a high color rendering index of 74.5 of resultant white laser diodes device structured by single‐phase LuAG:Ce,Mn TCs was obtained based on an efficient energy transfer process from Ce ³⁺ to Mn ²⁺ . This study will deepen the understanding of the crystal defects inside TCs on luminescence properties, as well as inspiring more exploration on defect control to develop high performance ceramic color‐convertor.

Lu₃Al₅O₁₂ (LuAG) is a famous scintillator that has the advantages of high efficiency, high light yield, and fast decay after being doped with active ions. F centers (oxygen vacancies with two electrons) and antisite defects are the most important defects and can greatly affect the scintillation performance in the bulk materials. However, the surface defects that strongly affect the spectrum of a single crystal (SC) and single crystal film (SCF) and the effect on the electronic properties have not been investigated. In this context, we investigate the surface structural and electronic properties of Lu₃Al₅O₁₂ using first-principles calculations. The Lu atoms are six-fold and seven-fold coordinated with the O atoms on the S1 and S2 surfaces. The surface oxygen vacancies and antisites have considerably lower formation energies than for the bulk. The oxygen vacancies in the bulk introduce the occupied states in the band gap. The surface electronic states are mainly located on the oxygen atoms and can be eliminated via oxygen vacancies.

A multi-channel energy transfer scheme was established in LuAG:Ce³⁺,Sm³⁺,Mn²⁺ phosphor ceramics to obtain a high color rendering index of white LDs.

In this study, fine Y ₂ O ₃ –MgO composite nanopowders were synthesized via the sol–gel method. Dense Y ₂ O ₃ –MgO composite ceramics were fabricated by pre‐sintering the green body in air at different temperatures for 1 h and then subjecting the sintered bodies to hot isostatic pressing at 1300°C for 1 h. The effects of pre‐sintering temperature on the microstructural, mechanical, and optical properties of the resulting ceramics were studied. The average grain size of the ceramics was increased, whereas their hardness and fracture toughness were decreased with increasing pre‐sintering temperature. A maximum fracture toughness of 1.42 MPa·m ^1/2 and Vickers hardness of 10.4 GPa were obtained. The average flexural strength of the ceramics was 411 MPa at room temperature and reached 361 MPa at 600°C. A transmittance of 84% in the 3–5 µm region was obtained when the composite ceramics were sintered at 1400°C. Moreover, a transmittance of 76% in the 3–5 µm region was obtained at 500°C.

Sesquioxides were considered as promising gain medium for high power ultrafast laser. Broadening of emission spectrum plays a crucial role in shortening the pulse width of laser. In this paper, the ratio of lutetium oxide and scandium oxide was adjusted to control the emission wavelength and spectral width. Highly sinterable Yb:(Lu _x Sc _1–x ) ₂ O ₃ nanopowders were synthesized through the glycine‐nitrate combustion process. Transparent Yb:(Lu _x Sc _1–x ) ₂ O ₃ ceramics were fabricated via vacuum sintering at 1750℃ for 10 h, among which Yb:(Lu _0.5 Sc _0.5 ) ₂ O ₃ ceramics have the highest transmittance, reaching 78% at 1100 nm. With increasing Lu ₂ O ₃ content, the emission wavelengths corresponding to the two transitions of Yb:(Lu _x Sc _1–x ) ₂ O ₃ were blueshifted 8 and 15 nm, respectively. Most importantly, from Yb:Sc ₂ O ₃ to Yb:(Lu _0.5 Sc _0.5 ) ₂ O ₃ , spectral broadening of the two emission wavelengths was observed by 9 and 16 nm, respectively. Thus, the Yb:(Lu _x Sc _1‐x ) ₂ O ₃ ceramics exhibiting high transmittance and broad emission band are promising for ultrashort pulse generation.

In this paper, a model to predict the thermal effects in a flashlamp-pumped direct-liquid-cooled split-disk Nd:LuAG ceramic laser amplifier has been presented. In addition to pumping distribution, the model calculates thermal-induced wavefront aberration as a function of temperature, thermal stress and thermal deformation in the gain medium. Experimental measurements are carried out to assess the accuracy of the model. We expect that this study will assist in the design and optimization of high-energy lasers operated at repetition rate.

“Defect engineering” was a valid strategy to modify the performance of LuAG:Ce scintillator, usually realized by Me ²⁺ /Me ⁺ co‐doping. To investigate the effects of Ca ²⁺ co‐doping on the scintillation properties of LuAG:Ce, a set of LuAG:Ce ceramics with Ca ²⁺ concentrations ranging from 0 to 0.5 at.% were manufactured. The absorption spectra, radioluminescence spectra (RL spectra), light yield, RL spectra as a function of temperature, decay time, and TSL curves of the ceramic products were carefully measured. With Ca ²⁺ co‐doping, the scintillation performance of LuAG:Ce ceramics was greatly improved. Especially for the 0.2 at.% Ca ²⁺ co‐doped one, it has a high light yield value of 24, 400 ph/MeV, a fast scintillation decay time of 48 ns, and a small slow component contamination. And the role of Ca ²⁺ in the scintillation mechanism of LuAG:Ce ceramics was also discussed in this paper.

Er ³⁺ ‐doped CaF ₂ transparent ceramics are promising mid‐infrared gain materials because of their utra‐low phonon energy as well as excellent physical, chemical, and optical properties. However, existing hot‐pressed and hot‐formed CaF ₂ ceramics are very difficult to be used in practical applications due to residual pores and weak polycrystallization, respectively. Here, we developed the high quality Er ³⁺ ‐doped CaF ₂ transparent polycrystalline ceramic by single crystal ceramization. The sample exhibits obvious polycrystalline structure, good mechanical properties, perfectly transmittance, and excellent mid‐infrared performance, which provides significant and wide‐ranging opportunities for advanced mid‐infrared gain materials.