Pure BSO Research Articles

Effective enhancement of light yield achieved in Bi4Si3O12 scintillation single crystals by doping with tantalum ions

Bismuth silicate (Bi4Si3O12, BSO) crystal is considered as a promising candidate for fabricating dual-readout calorimeters. Ta2O5 doped BSO crystals were successfully grown by the modified vertical Bridgman method. The crystals possessed about 80% transmittance in the region of 350nm-800 nm with an absorption edge at about 280 nm. The emission and excitation spectra only showed a wide band which could be ascribed to the typical peaks of Bi3+. The light yield of BSO crystals could be improved effectively by doping Ta2O5, and the optimized concentration was about 1 mol%, dramatically improving the light output to about 150% of pure BSO crystals. Both the experimental results and theoretical calculations showed that doping Ta5+ ion could reduce the band gap and effectively enhance the light absorption, which was beneficial to generate more electron-hole pairs and promote its emission and light yield. Ta5+ ion is an effective candidate among the transition metal ions for improving the light output of BSO crystals.

Characterization of mixed Bi4(Ge[formula omitted]Si[formula omitted])3O12 for crystal calorimetry at future colliders

Bismuth germanate (BGO) is a well known high density scintillating material widely used in many applications such as high energy physics and medical imaging. Bismuth silicate (BSO) features properties similar to BGO in terms of stopping power and Cherenkov photon yield with a lower scintillation light output but faster decay time, thus being more attractive for applications in high-rate environments. Mixed crystals such as Bi 4 (Ge x Si 1 − x ) 3 O 12 (BGSO, with x varying from 0 to 1) make it possible to optimize decay time and light yield based on the detector needs. A characterization campaign of the optical and scintillation properties of two sets of BGSO mixed crystals with Ge fraction varying from 0 to 100% was performed. A coincidence time resolution (CTR) at 511 keV of 208 ±2 ps FWHM was measured for a 2 × 2 × 3 mm 3 pixel with 40% Ge, while the optimum value obtained for the effective decay time is 49.9 ±1.8 ns for a 6 × 6 × 0.7 mm 3 plate-shaped sample with 30% Ge. Furthermore the smallest slow decay time component achieved is 101 ±2 ns and is obtained for the plate-shaped sample with 30% Ge, while the largest is 236 ±5 ns for a pure BGO sample with the same geometry. In addition we demonstrated the possibility to efficiently separate the Cherenkov and scintillation light produced in a pure BSO sample. Such a technique could be exploited in a crystal-based dual-readout calorimeter to improve the energy resolution for hadronic showers and jets.

Optical and scintillation properties of Bi4Si3O12:RE (RE=Eu3+, Sm3+, Ho3+, Tb3+) single crystals

Abstract Bi4Si3O12:RE (BSO:RE, RE = Eu3+, Sm3+, Ho3+, Tb3+) crystals were grown by the modified vertical Bridgeman method, and doping effects on scintillation properties were investigated. Under γ-ray irradiation, the light yield of BSO doped with small doses of Eu3+ increases slightly, and the energy resolution improves significantly compared to pure BSO, therefore the ability of distinguishing between particles will be improved for BSO crystals with a small amount of Eu3+ dopant. The results show that a small amount of Eu3+ doping can sensitize the Bi3+ ions. The sensitization effect enables the reduction of intrinsic defects, and thus improves the scintillation properties. However, the relative light yield of BSO:Tb (1.0 mol%) crystal is 4.3%, which is smaller than 5.0% of pure BSO. The improved light yield and energy resolution in the BSO:Eu and BSO:Sm crystals are considered an impressive achievement in the optimization of this scintillator which is already suitable for applications such as dual-readout calorimeters and homogeneous hadron calorimeters.

Tunable Optical Behaviour and Room Temperature Ferromagnetism of Cobalt-Doped BaSnO3 Nanostructures

In this work, the effect of Co doping on the structural, vibrational, morphological, optical and magnetic behaviour of BaSnO3 nanostructures is reported. Pure and Co (1,3, and 5%)-doped barium stannate (BSO) nanostructures were prepared by conventional hydrothermal technique followed by calcination at 900 °C for 5 h. The single crystalline cubic phase was identified by XRD analysis and structural distortions associated with Co doping were evidenced by variation in microstarin and crystallite size. FTIR and Raman studies further confirm the structural quality of the prepared samples. FESEM analysis revealed the mixed morphology of prepared samples, and the chemical compositions of all the samples were analysed using EDAX studies. The absorption studies revealed the incorporation of dopant ions and their effect on the bandgap subsequently in samples. The presence of defects and paramagnetic centres in the samples were confirmed by PL and EPR analyses. Magnetization studies demonstrated that pure BSO exhibits characteristic diamagnetism at room temperature and the addition of Co into Ba–Sn–O lattice drives the F-centre exchange interactions which results in the ferromagnetic behaviour. Hence, the occurrence of diamagnetic to ferromagnetic transition at room temperature with addition of Co as a dopant was identified.

MAGNETO-OPTIC STUDY OF CHROMIUM DOPED BI12SIO20

Faraday rotation in Bi12SiO20:Cr (BSO:Cr) has been investigated on (100) direction at room temperature using refractive index data in the spectral region 700 – 850 nm. Verdet constant (V) spectrum is determined in the same spectral region for this crystal. The Verdet constant spectrum of pure BSO can be described by the linear dependence V-1 (λ 2) (λ is the wavelength of the light). The Cr-ions in the sillenite crystal lattice cause a deviation of Verdet constant from the mentioned linear dependence in the spectral region of the absorption impurity structure. The magneto-optic anomaly factor γ is also investigated.

Influence of light on the magneto­electric effect in Cr‐doped Bi12TiO20

Sillenites are well known and promising materials for holographic memory, because of a significant photorefractive effect. We have investigated Cr‐doped BTO, pure BSO, and BGO single crystals for the magnetoelectric properties. Using light, an oxidation state of chromium dopant in sillenite Bi12TiO20 was manipulated that resulted in a sign change of the magnetoelectric effect. This change of sign correlates with different transformation properties of spinors corresponding to the states with integer and half‐integer spins.

Fabricaion of improved novel p–n junction BiOI/Bi2Sn2O7 nanocomposite for visible light driven photocatalysis

Abstract A series of novel p−n junction photocatalysts BiOI/Bi 2 Sn 2 O 7 (BiOI/BSO) were successfully fabricated via a facile hydrothermal method. The phase structures, morphologies and optical properties of the as-prepared samples were studied by XRD, TEM, HRTEM, BET, XPS, UV–vis DRS and photoluminescence (PL) spectroscopy. The results showed that BiOI/BSO heteronanostructures displayed much higher photocatalytic activity than pure BSO and BiOI for the degradation of rhodamine B (RhB). The best photocatalytic activity of BiOI/BSO with almost 99.9% RhB degradation situated at molar percentage ratio of 4% after 6 h irradiation. The enhanced photocatalytic performance of BiOI/BSO could be mainly attributed to the formation of the heterojunction between p-BiOI and n-BSO, which effectively restrains the recombination of photoinduced electron–hole pairs. Moreover, the study of radical scavengers affirmed that h + and •O 2 − were the primary reactive species for the degradation of RhB.

Emission spectra and thermoluminescence of rare-earth-doped bismuth silicate crystals grown by modified Bridgman method

Abstract Pure and rare-earth-doped bismuth silicate (BSO) crystals were grown in the same condition by the modified Bridgman method. UV exited florescence and thermoluminescence (TL) glow curves were investigated. The emission spectra of BSO crystals doped with Ce 3+ , Y 3+ , Gd 3+ and Yb 3+ ions respectively are similar to that of pure BSO crystal with a band at about 480 nm, but Dy 3+ and Eu 3+ doped BSO crystals show sharp emission peaks. Especially, the emission intensity of BSO:Dy is much higher than that of pure BSO crystal. Pure and Y 3+ , Gd 3+ and Yb 3+ ions doped BSO crystals have similar TL glow curves but Eu 3+ doped BSO crystal has extra strong peaks at 380 nm and 560 nm. No thermoluminescence is detected for BSO:Ce crystal, which implied BSO:Ce has large radiation hardness. It was suggested that Dy 3+ ions replace some Bi 3+ ions in BSO crystal and become new luminescent center. As a result, BSO:Dy crystal can be a potential excellent scintillator.

Vertical Bridgman Growth and Scintillation Properties of Doped Bi4Si3O12 Crystals

Pure BSO and Ce, Nd, Eu, Cr and Fe doped BSO crystals of high optical quality with 20×20×100mm 3 have been grown by the vertical Bridgman method. After measuring their transmission spectra, light outputs, FWHM energy resolutions and excitation-emission spectra, we summarized and explained the laws of doped effects on the scintillation characteristics. we can expect that Eu may be the most promising dopant candidate of the doped elements for improving the scintillation characteristics of BSO crystal.

Traps and recombination centers in pure and Co-doped Bi 12SiO 20 crystals

Abstract Pure and Co-doped (0.36-1.8 mol% Co) Bi 12 SiO 20 crystals have been studied. The temperature dependence of the dark and photoconductivity, thermostimulated currents and the spectral dependence of the photoconductivity have been measured. Exponentially distributed traps situated close to the conduction band bottom have been found in pure BSO crystals. It was found that Co atoms act as donors in BSO crystals, and two new traps at about 0.24 and 0.45 eV appear. Based on the observed thermal quenching of the photocurrent an identical energy position of the “slow” recombination centers has been determined in both type of crystals. The defects responsible for the “shoulder” absorption (at about 2.7 eV below the conduction band) have been found to play the role of these “slow“ recombination centers.

Liquid-phase epitaxial growth of bismuth silicon oxide single-crystal film: a new optically activated optical switch

A single-crystalline double-layered structure of a pure (80-microm)/doped (39-microm)/pure Bi(12)SiO(20) (BSO) substrate was grown for the first time by a new liquid-phase epitaxial growth to form an optical waveguide. The waveguide layer is BSO doped with CaCO(3) (0.1 wt. %) and Ga(2)O(3) (0.197 wt. %) and has a refractive index 0.07% higher than the substrate. The optical absorption coefficients were decreased by more than 1 order of magnitude by doping with the elements Ca and Ga. The high-sensitive photoconductivity of pure BSO was also reduced. Using these unique properties, we have constructed a new type of optically controlled planar optical switch.