Insights into the Microstructure and Transition Mechanism for Nd3+-Doped Bi4Si3O12: A Promising Near-Infrared Laser Material

X-ray-Induced Scintillation Properties of Nd-Doped Bi4Si3O12 Crystals in Visible and Near-Infrared Regions

Undoped, 0.5, 1.0, and 2.0% Nd-doped Bi₄Si₃O₁₂ (BSO) crystals were synthesized by the floating zone method. Regarding photoluminescence (PL) properties, all samples had emission peaks due to the 6p-6s transitions of Bi³⁺ ions. In addition, the Nd-doped samples had emission peaks due to the 4f-4f transitions of Nd³⁺ ions as well. The PL quantum yield of the 0.5, 1.0, and 2.0% Nd-doped samples in the near-infrared range were 67.9, 73.0, and 56.6%, respectively. Regarding X-ray-induced scintillation properties, all samples showed emission properties similar to PL. Afterglow levels at 20 ms after X-ray irradiation of the undoped, 0.5, 1.0, and 2.0% Nd-doped samples were 192.3, 205.9, 228.2, and 315.4 ppm, respectively. Dose rate response functions had good linearity from 0.006 to 60 Gy/h for the 1.0% Nd-doped BSO sample and from 0.03 to 60 Gy/h for the other samples.

Growth, spectra and continuous-wave 2.1 μm laser operation of a Ho3+-doped bismuth silicate crystal

A Ho3+:BSO crystal was grown using the Bridgman method. The 2.1 μm CW laser of the crystal was demonstrated.

Tm3+: Bi4Si3O12 crystal as a promising laser material near 2 μm: growth, spectroscopic properties and laser performance

We report on the crystal growth, spectroscopic properties and laser performance of Tm³⁺-doped Bi₄Si₃O₁₂ (BSO) crystal. The crystal was grown by the vertical Bridgeman method. The spectroscopic properties are investigated based on absorption and luminescence spectroscopy. Judd - Ofelt (JO) analysis is performed to calculate the spontaneous emission probabilities, branching ratio and the radiative lifetimes. The absorption spectrum, emission spectrum and gain cross-section spectra of Tm³⁺: BSO crystal are determined for the 2 μm transition. Luminescence decay kinetic of ³F₄ upper level was analysed in detail. The continuous-wave 2 μm laser with a maximum output power of 650 mW and a slope efficiency of 29.7% is demonstrated for the first time. The beam quality factor (M²) of Tm³⁺: BSO laser was about 1.03 at the maximum output level.

Confined-Melting-Assisted Synthesis of Bismuth Silicate Glass-Ceramic Nanoparticles: Formation and Optical Thermometry Investigation

Bismuth-based (nano)materials have been attracting increasing interest due to appealing properties such as high refractive indexes, intrinsic opacity, and structural distortions due to the stereochemistry of 6s² lone pair electrons of Bi³⁺. However, the control over specific phases and strategies able to stabilize uniform bismuth-based (nano)materials is still a challenge. In this study, we employed the ability of bismuth to lower the melting point of silica to introduce a new synthetic approach able to confine the growth of bismuth-oxide-based materials into nanostructures. Combining in situ temperature-dependent synchrotron radiation X-ray powder diffraction (XRPD) with high-resolution transmission electron microscopy (HR-TEM) analyses, we demonstrate the evolution of a confined Bi₂O₃-SiO₂ nanosystem from Bi₂SiO₅ to Bi₄Si₃O₁₂ through a melting process. The silica shell acts as both a nanoreactor and a silicon source for the stabilization of bismuth silicate glass-ceramic nanocrystals keeping the original spherical shape. The exciton peak of Bi₂SiO₅ is measured for the first time allowing the estimation of its real energy gap. Moreover, based on a detailed spectroscopic investigation, we discuss the potential and the limitations of Nd³⁺-activated bismuth silicate systems as ratiometric thermometers. The synthetic strategy introduced here could be further explored to stabilize other bismuth-oxide-based materials, opening the way toward the growth of well-defined glass-ceramic nanoparticles.

The Studies on Structure and Stability of CaBn Clusters

Calcium-boron systems have excellent properties of hardness, strength, and chemical stability, and we studied a series of CaB_n clusters to investigate their structures and relative stability. The results showed the most stable structures of CaB_n clusters are not planar. The B atoms tend to get together and form the planar ring to stabilize the structure, and the Ca atoms are coordinated to the periphery of the formations. The average binding energy (E_b), fragmentation energy (E_F), second-order energy difference (Δ₂E), adiabatic detachment energy (ADE), and adiabatic electron affinity (AEA) of the CaB_n clusters were calculated to investigate the relative stability and the ability of removing or obtaining an electron. As shown by the results, E_F and Δ₂E values had obvious odd-even alteration as n increased, which indicated that the formations CaB₄, CaB₆, and CaB₈ were more stable. The ADE values for CaB_n clusters with even values of n were higher than those with odd values of n, which indicated CaB_n clusters with even values of n had difficultly removing an electron. The AEA values of CaB₃ and CaB₇ were larger than the others, which meant CaB₃ and CaB₇ easily obtained an electron. These results provide a useful reference for understanding the formation mechanism and stability of the alkaline earth metal boride as well as guidance for synthesizing the CaB_n clusters.