Doped Single Crystals Research Articles

Investigation on the growth and complex impedance spectroscopy studies of pure and Mn2+ doped lithium sulphate monohydrate single crystals of various concentrations

Investigation on the growth and complex impedance spectroscopy studies of pure and Mn2+ doped lithium sulphate monohydrate single crystals of various concentrations

Magnesium-and-Zinc-Doped Lithium Niobate Crystals: Preparation and Characterization

Double-doping technology for growing lithium niobate crystals (LiNbO3:Mg:Zn) was developed. The crystals were highly homogeneous and had high optical damage resistance, so they show promise for use as photonic and nonlinear optical components. The crystals were grown from the LiNbO3:0.145 wt % Mg:1.98 wt % Zn batch. The batch was prepared by homogeneous doping. The proposed flowsheet can serve as the basis for a large-scale technology of doped lithium niobate single crystals.

K2YF5:Tb3+ single crystal: An in-depth study of spectroscopic properties, energy transfer and quantum cutting

Tb3+ doped K2YF5 single crystal was synthesized by the hydrothermal technique. Structure of material was analyzed by X-ray diffraction pattern and Raman spectra. The optical properties were studied through absorption, luminescence spectra and decay curves. Absorption spectra were used to calculate the bonding parameter (δ) and Judd-Ofelt intensity parameters (Ω2,4,6). The JO parameters and emission spectra have been used to estimate radiative properties such as transition probability (AR), branching ratios (βcal, βexp), lifetime (τcal) stimulated emission cross-sections (σλp, 10−22 cm2) and optical gain (σλp × τcal, 10−25 cm2 s) for 5D3→7FJ and 5D4→7FJ (J = 0 ÷ 6) transitions. The dominant interaction mechanism and energy transfer parameters between Tb3+ ions have been found by fitting the decay curves of 5D3 level to the Inokuti-Hirayama model. In addition, the quantum cutting process based on energy transfer between Tb3+ ions has also been studied for K2YF5:Tb3+ crystal.

Peculiar Structural Effects in Pure and Doped Functional Single Crystals of Complex Compositions.

Results of a detailed structural characterization of nominally pure and doped single crystals of scheelite, eulytin, and perovskite families obtained by melt methods were considered and analyzed. The influence of growth and post-growth annealing conditions on actual compositions of crystals is shown. The reasons for the coloration of the crystals are explained. A change in crystal symmetry due to crystal–chemical and growth reasons is considered. The use of structural analysis and X-ray absorption spectroscopy is substantiated to reveal the role of activator ions in the formation of statistical and local structures, respectively. A relationship between the distribution of activator ions over crystallographic sites and photoluminescent parameters of materials is established, which allows selecting optimal systems for the application. The combined results of studying single-crystal compounds of other classes (huntite, sillenite, whitlockite, garnet, tetragonal bronzes) allow formulating and summarizing structural effects that appeared in the systems and caused by various factors and, in many cases, due to the local environment of cations. A principal difference in the structural behavior of solid solutions and doped compounds is shown. The methodology developed for single-crystal samples of complex compositions can be recommended for the systematic structural studies of functional materials of different compositions.

Luminescence and Scintillation Properties of Dy3+ doped Li6Y(BO3)3 crystal

The orthoborate crystals with a wide optical bandgap allow different rare earth ions as an activator (Ce3+, Dy3+, Eu3+, etc.) to provide efficient luminescence. In the present study, Li6Y(BO3)3 pure and 4 mol% Dy3+ doped single crystals have been grown using the Czochralski method. The light emission of the grown crystals has been characterized by using X-ray luminescence, photoluminescence and thermoluminescence measurements. Intrinsic luminescence property has been observed for pure crystal at 330 nm and the characteristic emission of Dy3+ was observed in doped crystal under X-ray excitation. Photoluminescence study of the doped crystal at low temperature has shown the increased peak intensity with the decrease of temperature from 290 to 10 K. Decay time has been measured at the temperature ranging from 290 to 10 K which consists of three components in each stage. Thermally stimulated luminescence of both pure and 4 mol% Dy3+ doped LYBO crystals have been compared at low temperature from 320 K to 10 K. Scintillation β− counts measured from 300 K to 10 K. The performance of the doped crystal has been tested as a scintillator for thermal neutron imaging.

Growth, optical and scintillation properties of Gd3+ doped Bi4Si3O12 single crystals

Pure Bi4Si3O12(BSO) and Bi4Si3O12:Gd (BSO:Gd) crystals with nominal concentrate of 1.0–6.0 mol% Gd2O3 were grown by the modified vertical Bridgman method. The X-ray powder diffraction, transmission and fluorescence spectra have been investigated on BSO:Gd crystals. Scintillation properties of Gd3+ doped Bi4Si3O12 single crystals have been investigated. Doped with small amount of Gd2O3(1.0–6.0 mol%), the relative light yield and energy resolution of BSO crystals were improved significantly. The experimental data indicates that the sensitization effect of a small amount of Gd3+ doping enables the intrinsic defects reduce, and improve the light yield and a large amount of Gd3+ doping can cause the new crystal field distortion and further affect the intrinsic luminescence of Bi3+. These results indicate that BSO:Gd crystals could be one of the promising candidates for replacing BGO in some applications such as electromagnetic calorimeter and dual readout in nuclear or high energy physics.

Electron and Hole Trapping in Ce3+ - and Pr3+ -Doped Lutetium Pyrosilicate Scintillator Crystals Studied by Electron Paramagnetic Resonance

Electron and hole trapping was studied in the Ce3+ and Pr3+ doped Lu2Si2O7 scintillation single crystals (LPS:Ce and LPS:Pr) by Electron Paramagnetic Resonance (EPR). Detailed EPR measurements of the X-ray irradiated LPS crystals revealed that holes generated by irradiation are predominantly trapped at oxygen lattice ions creating O- centers. The same X-ray irradiation creates also electron type centers which were attributed to Lu2+ ions, where the trapped electron at Lu lattice ion is stabilized by a defect nearby, such as oxygen vacancy and Ir3+ impurity ion. Both the hole and electron centers can be thus considered as a bound small polarons, which makes the charge trapping in scintillation mechanism quite competitive. The hole O- and electron Lu2+ centers show thermal stability well above room temperature. The thermal decays of their concentrations correlate well with the appearance of the thermally stimulated luminescence glow peaks at 470-550 K. The presence of the same intrinsic traps in the Ce and Pr doped LPS crystals suggests that difference in the light yield of these crystals is an intrinsic property of the Ce3+ and Pr3+ activator centers in LPS lattice. Charge traps origin in this pyrosilicate structure and their role in scintillation mechanism is compared with the results previously described in literature in orthosilicates.

Ho3+ doped Na5Y9F32 single crystals doubly sensitized by Er3+ and Yb3+ for efficient 2.0 μm emission

The 2.0 μm spectral characteristics of the 980 nm LD pumped Er3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystals grown by an improved Bridgman method were investigated with the help of their absorption spectra, emission spectra and decay curves. The introduction of Yb3+ and Er3+ greatly improves the 2.0 fluorescence intensity through joint energy transfer processes from Yb3+ to Er3+, and Er3+ to Ho3+. The doping concentrations of 0.5 mol% Er3+ and 1.0 mol% Yb3+ ions were optimized to obtain the maximum 2.0 μm fluorescence intensities for the fixed 0.8 mol% Ho3+/1 mol% Yb3+ and 0.8 mol% Ho3+/0.5 mol% Er3+ doped Na5Y9F32 single crystals. Besides, according to the absorption and fluorescence spectra of the crystals, the absorption and emission cross-sections were calculated, and excellent gain performance was also obtained. Meanwhile, the maximum 2.0 μm emission lifetime of Er3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystal can reach ~21.82 ms. The energy transfer mechanisms among the three rare-earth ions were further investigated by calculating energy transfer micro-parameters (CDA) and efficiencies. The excellent properties in both intense emission at 2.0 μm and chemical stability obtained in the Er3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystals make them promising candidate material for 2.0 μm laser.

Optical investigation of Pr3+ doped CsSrI3 single crystals grown by EFG method

Current interest in halide scintillation crystals is ABX3:Eu (A = Cs, B = Ca, Sr, X = Cl, Br, I) material family. Among them, CsSrI3:Eu has been widely studied, but we still hope to study the performance of other ion-doped CsSrI3 crystals. In this work, we report the CsSrI3:Pr crystals with various Pr3+ concentrations are grown by Edge-defined Film-fed Growth (EFG) method for the first time. As Pr3+-doped CsSrI3 single crystal is non-equivalent substitution (Pr3+ → Sr2+), it may affect the growth and luminescent properties of the crystal. We have grown the CsSrI3:Eu and CsSrI3:Pr crystals and compared them with the decay time. By comparison, we found that Pr-doped CsSrI3 crystals has a better decay time than CsSrI3:Eu crystals.

Growth, Optical and Thermal properties of Co2+ doped copper tartrate single crystals at different environmental conditions.

Cobalt doped Copper Tartrate (CoCT) crystals were grown in silica gel medium using single diffusion methods at room temperature, passing semiconductor laser and passing various UV visible radiation. The optimum conditions were obtained by varying parameters such as gel concentration, pH of gel, gel setting time, the concentration of reactance. The presence of cobalt, copper, carbon, and oxygen is confirmed by the Energy dispersive X-ray spectroscopy (EDX). The crystals obtained, are regular or elongated shaped depending on the growth and environmental conditions. The grown crystals are characterized by FTIR and PXRD. TGA studies explain the thermal behavior of the grown CoCT crystal. UV-Vis-NIR transmission spectroscopic analysis measured the energy gap and, to study the optical transparency of the grown crystals.

Growth and red-orange emission of Sm3+ doped SrAl12O19 single crystals

Sm:SrAl12O19 (Sm:SRA) single crystals with dopant concentration of 1 and 8 at.% have been successfully grown by the Czochralski method. Polarized absorption spectra, emission spectra, as well as the lifetime measurements were performed. The absorption cross-section was calculated to be 1.97 × 10−20 cm2 at 404 nm for σ polarization and 1.13 × 10−20 cm2 at 405 nm for π polarization, respectively. The highest emission cross-section at 593 nm was calculated to be 0.58 × 10−21 cm2 for σ polarization and 0.45 × 10−21 cm2 for π polarization, with full width at half maximum (FWHM) of 7.73 nm and 7.42 nm, respectively. Judd-Ofelt (JO) intensity parameters (Ω2, Ω4 and Ω6) and radiative properties for the important luminescent level of Sm3+ ions were derived by using the polarized absorption spectra of 8 at.% Sm:SrAl12O19. The fluorescence lifetime of 1 at.% and 8 at.% Sm:SrAl12O19 crystals were calculated to be 2.83 ms and 2.11 ms, respectively. The results indicate that the Sm:SRA crystal would be potential laser material for red-orange oscillation pumped by commercially 405 nm laser diode.

Growth and mid-infrared luminescence property of Ho3+ doped CeF3 single crystal

A Ho3+-doped CeF3 crystal was successfully grown for the first time using the Bridgman method, and its spectral properties were studied. By analyzing the absorption and emission measurements of the Ho:CeF3 crystal with the Judd–Ofelt theory, the intensity parameters Ω2,4,6, emission cross-sections, gain cross-sections, and excited state lifetimes were calculated. It was found that the peak absorption cross-section around 447 nm is 0.4339 × 10−20 cm2, which matched to the commercially available blue laser diode lasers. The 2.0 μm excitation emission of the Ho:CeF3 crystal corresponding to the stimulated emission Ho3+:5I7→5I8 transition has an emission cross section of 0.24 × 10−20 cm2 with FWHM of 146 nm.

Crystal growth, spectroscopic, second and third order nonlinear optical spectroscopic studies of L-phenylalanine doped ammonium dihydrogen phosphate single crystals

The frequency doubling and tripling can be reached for Nd:YAG laser beam using the single crystal of ammonium dihydrogen phosphate (ADP). The growth and characterization of pure and L-phenylalanine doped ADP crystals are considered in the present contribution. The transparent good quality single crystals are grown using low temperature solution growth technique. The functional group alteration is studied using FT-IR spectroscopy. The larger improvement is observed in linear and nonlinear optical properties of ADP crystals on doping by L-phenylalanine. The reduction in charge carrier density is observed in photoconductivity spectra of all the grown crystals.

Unusual magnetic phenomena in dynamic torsion studies of fullerene Rb3C60

In dynamic experiments using a highly sensitive torsion technique, the magnetic properties of the doped Rb3C60 single crystal are studied over a wide temperature range. The critical temperature of the superconducting transition Tc, the critical magnetic field Hc1, the pinning forces of both the Abrikosov vortices and the magnetic moments of dipoles at T >> Tc, at which relaxation processes are important, are determined and investigated. It was shown that the structural transition Fm3m-Pa3 at T = 260 K is accompanied by a reformation of the magnetic structure. Both the usual peaks at T ∼ 160–250 K and the not quite ordinary peaks of gigantic absorption of the energy of the oscillations, which shift to room temperature over time, were observed. The phenomenon is discussed in the framework of the cooperative Jahn-Teller effect, taking into account possible orbital and spin ordering. The relaxation processes at room temperatures (T ∼ 300 K) were studied. After many days of exposure (annealing) of fullerene at T ≥ 40 °C, in experiments with cooling from room temperatures, phenomena typical for a superconducting transition with giant pinning and damped oscillations were observed at T ∼ 200 K. The results of studies of magnetic phase transitions at T = 180–200 K in pure fullerite C60 (99.98% Term. Sublimed), which are related to the detected unusual magnetic phenomena in fullerene Rb3C60, are presented.

Elucidation of site symmetry, location, bond, ground state of Cu2+ ions in lithium sulphate monohydrate single crystal through EPR and optical studies

The highly efficient non linear optical (NLO) lithium suphate monohydrate (LSMH) single crystal with well-developed faces is obtained in a few days by slow evaporation of aqueous solutions at room temperature. Small amount of copper II sulphate pentahydrate is added as the paramagnetic impurity into the system. The powder XRD study shows the monoclinic cell dimension of Cu2+ doped LSMH single crystal. Also FTIR analysis reveals the existence of host in a crystal. The single crystal EPR investigation talks about the presence of copper ion. Even though more than one site is noticed, two are followed and reported. The principle values g and A parameters were calculated for both the sites. The spin Hamiltonian parameters found for both the sites, indicate the rhombic local crystal field symmetry around the impurity ion Cu2+, which is further confirmed by optical absorption studies. Interestingly, both the paramagnetic ions enter the lattice interstitially. The type of bonding between the metal ligand bands for site I and site II are found to be moderate ionic and covalent nature. The ground state wave function of both the sites are observed as dx2−y2, which is also supported by Rache parameter and optical studies.

Molecular doped organic semiconductor crystals for optoelectronic device applications

In this review, we give a timely summary of the current progress of molecular doped organic semiconductor single crystals in terms of material selection, crystal growth, resulting properties and device applications.

Chemical vapor transport growth of bulk black phosphorus single crystals

Recent progress in growth of bulk black phosphorus single crystal by CVT method has been briefly reviewed with the emphasis on reaction system, nucleation and growth mechanism as well as advancement in growth of doped BP bulk single crystal.

Impact of bio-organic additive chlorophyll-b of Ficus religiosa, on optical, thermal, mechanical behaviors of KDP optical single crystals: A novel NLO material

The effects of 0.5 mol % of Ficus religiosa chlorophyll-b doped potassium dihydrogen orthophaspate single crystals (CHLBKDP) grown by slow evaporation technique, on the optical, thermal, mechanical parameters, photoluminescence and SHG efficiency have been investigated. The Vicker’s microhardness study reveals that the addition of Chl-b decreases the hardness of the KDP. Thermal studies indicate that the decomposition temperature of Chl-b doped KDP is more than that of pure KDP. The influence of doping Chl-b on the optical, thermal and mechanical behavior has been studied in this present investigation. The fluorescence spectrum at 451 nm and 676 nm indicated blue and red light emission. It is observed that addition of Chl-b improves the optical, thermal and mechanical properties of the crystal. From the optical parameter analysis, it is confirmed that, the grown crystal (CHLBKDP) is an apt candidate for optoelectronics applications. The organic material (Chl-b) doped KDP it may be applied in healthcare application namely medical imaging process under Photonics. In the present work, the idea of organic (Chl-b) doped KDP has been applied to a vast range to analyze the characteristics of materials in terms of electrical conductivity and response to light and temperature have been achieved. Materials which revels these properties are applicable in the power grid, sensors, electronics and lenses.

La3+ and Er3+ co-doped Y2O3 transparent ceramics with a tunable refractive index and long coherence lifetime

La3+ is used as an index modifier to tune the refractive index of Er3+ doped Y2O3 transparent ceramics without reducing the coherence lifetime of Er3+ 4I13/2−4I15/2 transition. La3+ and Er3+ are incorporated into Y2O3 through a solution-phase nanoparticle synthesis and nanoparticles are sintered into transparent ceramics by hot isostatic press. The maximum La3+ doping concentration is about 10%, which increases the refractive index of Y2O3 by 0.009 (Δn/n = 0.48%). La3+ doping doesn’t reduce Er3+ optical coherence lifetime. The homogeneous linewidth of Er3+(20 ppm) 4I13/2−4I15/2 transition in La3+ doped Y2O3 ceramics is about 10 kHz at 2 K and 0.65 T, which is close to the reported homogeneous linewidth in Er3+ doped Y2O3 ceramics and single crystals. Such La3+ Er3+ co-doped Y2O3 ceramics are proper materials to fabricate optical waveguides for quantum memory applications.

Physico-chemical, structural, optical and NLO studies on pure and La3+ doped l-arginine acetate crystals

Pure and La3+ doped single crystals of l-arginine acetate (LAA) have been grown well from through slow evaporation method in aqueous environment. The Crystalline nature can be confirmed by powder X-Ray Diffraction (XRD) Analysis. The function groups with possible stretching/bonding were identified through FTIR (Fourier Transform Infrared Spectroscopy) and Fourier Transform Raman Spectroscopy (FT-Raman) analysis. The good optical properties of La3+ doped LAA crystals were found through UV–Visible spectral analysis. Nonlinear optical (NLO) behavior through Kurtz’s method reveals that the dopant has increased the efficiency. Further, grown crystals has examined for thermal (TGA, DTA), mechanical (Vicker’s), dielectric (LCR) and photo conductive (picoammeter) properties enhanced with La3+ dopant and the results are interpreted and discussed.