Low temperature TL glow curves in KBrxI1-x mixed crystals

Thermoluminescence (TL) glow curves were recorded in KBr, KI and in different compositions of KBr_xI_1-x mixed crystals at LNT. For this a cryostat has been designed and fabricated. The glow peaks observed in these crystals have been attributed to differnent colour centers.     

Thermoluminescence and optical absorption studies in γ-irradiated KClxBr1–x mixed crystals

Thermoluminescence (TL) and optical absorption measurements have been carried in γ-irradiated KCl, KBr and various compositions of KCl_xBr_1–x mixed crystals as a function of irradiation time and composition. The position of the main glow peak (high temperature peak) and F-band position are found to vary non-linearly with composition, showing a correlation between colour centers and TL. The TL peaks have been analysed by numerical fitting and the trap depths and frequency factors have been calculated for different compositions of the mixed crystals. The thermal ionisation energy of F-centers has been calculated for the mixed crystals and it is found to vary non-linearly with composition. The results obtained in mixed crystals have been discussed in terms of high disorder present in them.     

Thermoluminescence of Sr1–xEuxF2 + x Solid Electrolytes

Thermoluminescence (TL) studies have been carried out in different compositions of Sr_1–xEuxF_{2 + x} mixed crystals as a function of X-irradiation time. Three groups of TL glow peaks in the temperature ranges (340, 360 ∼ 370 K), (460 ∼ 475, 540 ∼ 575 K) and (615 ∼ 635, 680 ∼ 720 K) are identified. The growth rates of different glow peaks have been compared with each other to estimate the growth kinetics. The three groups of TL glow peaks are attributed to thermal ionization of radiative impurity centers, different stages of F-centers and other kinds of defect centers such as F-interstitials. The shift in the glow peak maxima is perhaps due to unassociated impurities surrounding F-centers causing a change in configuration. The concentration quenching of TL output due to increased europium is pertinent in Sr_1–xEuxF_{2 + x} mixed system.     

Effect of change of state of aggregation of impurity on tl and microhardness of KClxBr1–x mixed crystals doped with Ca2+

Microhardness and Thermoluminescence (TL) measurements have been made in KCl_xBr_1–x mixed crystals doped with Ca²⁺ impurity. The variation of hardness in undoped and Ca²⁺ doped KCl_xBr_1–x crystals with quenching temperature is investigated. TL studied of KCl_xBr_1–x crystals doped with Ca²⁺, both in as-grown state and after quenching them from various elevated temperatures indicate that the positions of the glow peak which has been attributed to F-centers is found to depend upon the state of dispersion of impurity.     

Effect of Flux on thermoluminescence in Flux-grown BaFCl crystals

BaFCl crystals have been grown using BaF₂ and BaCl₂ by flux technique. Glow curves, optical absorption, and TL emission spectra of x/r — irradiated crystals are studied. The results have been compared with those BaFCl crystals grown from NaF flux so as to study the effects of flux on these properties. It is found that crystals grown from BaF₂ flux are relatively purer. An additional TL glow peak at 460 K, an optical absorption band at 775 nm and TL emission band at 485 nm have been obtained in the presently grown crystals. The additional glow peak, optical absorption band have been attributed to F(¯F) aggregate centers, whereas the 485 nm TL emission band to impurity centers.     

Kinetics and Trapping Parameters of Thermoluminecence of Sr1−xEuxF2+x Mixed Crystrals

The kinetics and trapping parameters of thermoluminescence of Sr_1−xEu_xF_2+x mixed crystals have been calculated by using different methods. The trap depths, frequency factors, and order of kinetics of glow curve pattern in several compositions of the system revealed variations with composition.     

Thermoluminescence studies of Al2O3 crystals doped with Cobalt impurity

Thermoluminescence (TL) studies of cobalt-doped Al₂O₃ crystals irradiated with X-rays have shown that the TL glow curve consists of three peaks at 105, 195 and 260°C. Bleaching, annealing and quanching studies have been performed in order to understand the nature of colour centers responsible for the formation of the three peaks. The values of the fundamental parameters like trap depth and frequency factor are estimated from TL data and the results obtained are discussed.     

Etching and kinetics of dissolution of Mo1−x WxSe2 single crystals

The dislocation etchant has been established for single crystals of Mo_1−xW_xSe₂ system. Effect of concentration of an etchant on the etch rate has been discussed. The morphology of etch pits is also described. The etch activation energies for all the compositions of these crystals for a particular concentration (7 N) of an etchant has been found out. The etch activation energies for a particular composition (x = 0.4) of crystals with different concentrations of an etchant have been investigated and the results have been discussed.     

A thermoluminescence study of Z2-centres in terbium-doped NaCl crystals

Thermoluminescence (TL), optical absorption are used to correlate thermal annealing of Z₂-centres with TL peak occurring around 110 °C in Terbium doped NaCl crystals. The TL glow peak occurring around 190 °C it attributed to the thermal annealing of F-centres. The thermal activation parameters are calculated for both Z₂- and F-centre peaks.     

Effect of plastic deformation of the thermoluminescence of γ-irradiated NaCl and KCl Crystals

The overall thermoluminescence (TL) intensity of γ-irradiated NaCl crystals initially increases and then decreases with the number of newly-created dislocations. However, the overall TL intensity of γ-irradiated KCl crystals increases with the increasing number of newly created dislocations. The TL spectra are recorded for different plastic deformations at different temperatures. It is found that the plastic deformation has no considerable effect on the TL spectra of γ-irradiated NaCl and KCl crystals. Trap destruction model and trap competition model are discussed for the decrease in the TL intensity with deformation of the crystals. The physical ideas behind the increases in the relative intensity of glow peaks and the appearance of new glow peaks are explored.     

Optische Eigenschaften von Wismut–Antimon-Aufdampfschichten

The change in position and in magnitude of absorption peaks due to interband transitions E_i (i = 1, 2, 3) for Bi_xSb_1–x evaporated layers have been studied for different compositions in the range 0 ≦ (1 − x) ≦ 0.30 in the visible part of the spectrum. It has been founded nonlinear shiftings for all absorption peaks in function of layer composition. The joint density of states due to transition E₂ is more sensitive as the two other transitions with modification of alloy composition.     

High-temperature X-ray irradiation induced thermoluminescence and half-life calculations in NaYF4 polycrystalline samples

Elevated irradiation temperature studies with NaYF₄ samples reveal that the intensity of the two glow peaks observed around 120 and 180°C enhances. The effect of temperature of irradiation (T_irr) on the sensitisation of the both peaks are studied. The half lives of these glow peaks were calculated and concluded that the half lives of these peaks decreases with the increase in irradiation temperatures.     

Activation parameters of some differently prepared thermoluminophors

For some thermoluminophors (LiF, Li₂B₄O₇, CaF₂, and CaSO₄) a thermoluminescence peak analysis was made in order to characterize the observed processes by their activation parameters. The resulting values for E₀ and K as well as the kinetic order are given. For different sample geometry the glow curve parameters can slightly be altered but the activation parameters remain almost invariant. For LiF the whole TL curve was described by a spectrum of resolved, independent levels and corresponding peaks.     

Growth and thermal studies on pure ADP,KDP and mixed K1‐x(NH4)xH2PO4 crystals

The investigations on the formation of mixed crystals of ammonium dihydrogen orthophosphate (ADP) and potassium dihydrogen orthophosphate (KDP) i.e. potassium ammonium dihydrogen phosphate, K_1‐x(NH₄)_xH₂PO₄ have been presented in this paper. Pure and mixed crystals of ADP and KDP have been grown by slow evaporation technique from the supersaturated solution at an ambient temperature 26±1 °C for ammonium concentration x in the range 0.0 ≤ x ≤ 1.0 in the case of mixed crystals. Crystal compositions were determined by flame atomic absorption spectroscopy and chemical analysis. The results of the X‐ray analysis of the grown crystals are also reported. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study the kinetic process of dehydration and the high temperature phase behaviour. DTA showed the distinct thermal events attributed to dehydration of ADP, KDP and K_1‐x(NH₄)_xH₂PO₄. The results of thermal analysis and chemical analysis are consistent with each other. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Low-temperature Thermoluminescence Glow Curves in NaCl Crystals Doped with Yttrium

Thermoluminescence glow curves were recorded in undoped and yttrium-doped NaCl crystals X-irradiated at liquid nitrogen temperature (LNT). An attempt is made to assign the glow peaks observed to different centres such as V_k-centres and yttrium related centres etc.     

Growth and characterization of mixed Sr: Ca tartrates

Single crystals of Sr_1−xCa_xC₄H₄O₆ · 4 H₂O of different compositions and forms were grown by controlled diffusion of ions through suitable silica gels and characterized. Pycnometer density, lattice parameter, dislocation density, dissolution, cleavage, etc. are some of the interesting features which distinguish mixed crystals from the pure ones.     

Single crystals growth and absorption spectra of Cr-doped Al2−xInx(WO4)3 solid solutions

The growth conditions of pure and Cr³⁺-doped Al_2−xIn_x(WO₄)₃ single crystals, using top-seeded solution growth (TSSG) technique, have been studied. A series of experiments have been performed at different In concentrations, x=0.0, 0.3, 0.6 and 1.0, as well as at different concentrations of Cr³⁺ (0.0, 0.1, 0.2, 0.5 and 1.0) in at% with respect to the initial total concentration of Al and In in the starting solutions. The basic parameters of the crystal growth are varied over a wide range: seed orientation, speed of rotation, axial and radial temperature differences in the solution and the solution cooling rate. The investigated relations between the basic defects in the crystals and these parameters result in determination of the optimal conditions for growth of defect-free crystals. Distribution coefficients of Al, In and Cr have been determined, so the growth of crystals with given compositions is possible. Values of Dq/B (crystal field strength) for the various crystal compositions are calculated from the optical absorption spectra. The calculated values show that the discussed solid solutions have weak crystal field and are suitable for media with broadband emission spectra.     

Effect of Pb on the properties of Sr2YRu1‐xCuxO6 crystals grown from PbO‐PbF2 solutions at high temperatures

Single crystals of Sr₂YRu_1‐xCu_xO₆ with x=0 and x=0.1 were grown using PbO‐PbF₂ based solutions at different temperatures in the range 1150–1350°C. The influence of Pb from the solutions and the Cu from the solid solutions of Sr₂YRu_1‐xCu_xO₆ on the resulting crystals was studied using microstructure and magnetic property measurements. The peaks in the powder X‐ray diffraction patterns and Raman spectra do not change in the case of x=0 crystals but shift in the presence of Cu. A diamagnetic transition indicative of superconductivity was observed in the presence of Cu and an antiferromagnetic behavior with x=0. Based on these results it is concluded that Pb may not be incorporated in the crystals and even if it does the influence is not observed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermoluminescence and Optical Absorption Studies of Z1 Centers in KCI Crystals Doped with Praseodymium

Thermoluminescence (TL) of Pr-doped KCI is studied. The influence of pre-heat treatment and optical bleaching of the glow curves and the production of Z₁ centers are discussed. The glow curves of KCI containing 1062 ppm of praseodymium (Pr) shows one shoulder at 365 K (T₁) and two peaks around 408 K (T₂) and 443 K (T₃), respectively. Bleaching of X-irradiated crystals shows that the peak T₂ is enhanced whereas other two (T₁, T₃) get suppressed. Optical absorption studies of the crystals before and after F-bleaching shows that the F-band decreases and shifts towards longer wavelengths. The decrease is accompanied by broadening towards the longer wavelength. The T₂ peak is attributed to Z₁ centres. It is shown that T₁ corresponds to shallow centers and T₃ peak is attributed to F-centers.     

Some transport measurements of WSe2-x single crystals

Electrical resistivity and its anisotropy, thermoelectric power and temperature coefficient of resistivity of WSe_2-x crystals have been measured (0.01 ≦x≦ 0.1) in the temperature range 300–448 K. Variations of these physical properties with respect to temperature and composition have been examined. The observed results are discussed in the light of semiconducting nature of the material.