Yiqiang Shen

Microstructure, optical, and scintillation characteristics of Pr3+ doped Lu3Al5O12 optical ceramics

0.5, 1.0, and 5.0 at. % Pr3+ doped Lu3Al5O12 (Pr:LuAG) optical ceramics are fabricated and compared with Bi4Ge3O12 (BGO) and Pr:LuAG single crystals as for their optical, luminescence and scintillation properties. Radio-luminescence intensity of the fast UV emission based on 5d1→4f Pr3+ transition reaches up to 20 times of that of BGO single crystal reference scintillator. Photoelectron yield of the best performing 0.5 at. % Pr:LuAG ceramic sample is about 1002 phels/MeV, about 30% lower than that of BGO reference sample and about 65% lower than that of Pr:LuAG single crystal. The trapping phenomena at grain boundaries and/or structural defects are proposed as the main cause of degradation of the scintillation response of the Pr:LuAG optical ceramics.

Composite YAG/Nd:YAG transparent ceramics for high-power lasers

Composite YAG/2.0at%Nd:YAG transparent ceramic was fabricated by solid-state reactive sintering a mixture of commercial α-Al₂O₃, Y₂O₃, and Nd₂O₃ powders with tetraethoxysilane (TEOS) and MgO as sintering additives. A fully dense YAG/2.0at%Nd:YAG ceramic with an average grain size of ~20μm was obtained by vacuum sintering at 1750°C for 50h. There are almost no pores or second phases present at grain boundaries or inner grains. The in-line transmittance reached 83.6% at the lasing wavelength of 1064nm and 82.0% at 400nm. The porosity of the sample was at the level of several vol ppm. The composite YAG/2.0at%Nd:YAG transparent ceramics are promising to generate high-energy laser.

Scintillation properties of Pr3+-doped optical ceramic and single crystals of Lu3Al5O12

We used gamma spectroscopy to study scintillation properties of the Pr3+-doped lutetium aluminium garnet material (LuAG:Pr). Characteristics of LuAG:Pr optical ceramic samples (0.5-5 mol % Pr3+ content) are compared with those of LuAG:Pr single crystal. Nphels photoelectron yield of Pr3+-doped optical ceramic samples reaches up to 30-40 % of that of LuAG:Pr crystal, while their energy resolution values are closer. Non-proportionality effect in optical ceramic samples is noticeably smaller with respect to single crystal below 500 keV.

Magnetic properties of R(Fe1−xCox)11.3Nb0.7 (R=Y,Ho) compounds

Magnetic properties R(Fe1-xCox)(11.3)Nb-0.7 compounds have been investigated. All of the compounds crystallize in the tetragonal ThMn12 structure. The unit cell volume slightly decreases with increasing Co content for both systems. Curie temperature (T-C) almost increases linearly with increasing Co content for both systems. The maximum of saturation magnetization (M-s) appears around x=0.2 in Ho(Fe1-xCox)(11.3)Nb-0.7 and x=0.15 in Y(Fe1-xCox)(11.3)Nb-0.7 compounds at 5 K. The easy magnetization directions of all compounds are along the crystallographic c axis at room temperature. Thermomagnetic analysis shows that there exists no spin reorientation in the whole ordering temperature range. The magnetocrystalline anisotropy field B-a of Y(Fe1-xCox)(11.3)Nb-0.7 exhibits a maximum with x=0.10 at 5 K and x=0.05 at room temperature, while B-a of Ho(Fe1-xCox)(11.3)Nb-0.7 decreases monotonically with the increasing Co content at room temperature. First-order magnetization process (FOMP) has been observed in Ho(Fe1-xCox)(11.3) compounds at low temperature