Thermal and optical properties of Cu(II)-doped magnesium rubidium sulfate hexahydrate crystals

Single crystals of pure and cupric ion (Cu(II))-doped magnesium rubidium sulfate hexahydrate (MRSH) were prepared by slow evaporation of saturated solution technique (SEST) and the influence of dopant Cu(II) on the MRSH crystals has been investigated. Incorporation of Cu(II) into the crystalline matrix was confirmed by energy dispersive spectroscopy (EDS) and electron paramagnetic resonance (EPR) spectroscopy. Thermogravimetric (TG) analysis of the doped sample reveals the faster rate of degradation. EPR spectrum of the MRSH both at room temperature and at 77 K indicates the presence of Cu(II) in the interstitial position. The grown crystals were also characterized by UV–VIS and IR spectroscopy. The surface morphology of the doped sample studied by scanning electron microscopy (SEM) indicates different morphology at various magnifications. The non-linear optical (NLO) property measured using second harmonic generation (SHG) efficiency test reveals that the non-linearity is not facilitated by doping of Cu(II).     

Effect of magnesium doping on the properties and crystalline perfection of bis(thiourea)zinc(II) chloride crystals

In this article, the effect of magnesium doping on the properties of bis(thiourea)zinc(II) chloride (BTZC) crystals has been described. The incorporation of Mg(II) into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy and quantified by inductively coupled plasma technique. The powder X-ray diffraction and FT-IR spectral analyses indicate that the crystal undergoes considerable stress as result of doping. SEM studies of pure and doped samples indicate the formation of structural defect centers in BTZC crystals. The TG?CDTA studies reveal the purity of the materials, and no decomposition is observed up to the melting point. Improved crystalline perfection by doping is observed by high-resolution X-ray diffraction. High transmittance is observed, and the cutoff ?? is ~295?nm.     

Growth and thermal kinetics of pure and cadmium doped barium phosphate single crystal

Non-isothermal kinetic parameter of pure and cadmium-doped barium phosphate single crystal grown by room temperature solution technique have been investigated. Single crystal X-ray diffraction establishes grown crystal to be orthorhombic in nature. Scanning electron microscopy supplemented with energy dispersive X-ray analysis was used to study the surface features and to find the exact stoichiometric composition of the grown crystal. Fourier transform infrared spectroscopy studies confirm the presence of various functional groups. The effect of cadmium doping on pure barium phosphate single crystal was studied using thermogravimetry analysis. Thermogravimetry studies shows that the pure crystal was stable up to a temperature of 330 °C whereas doped crystal was stable up to a temperature of 240 °C, i.e., pure crystals were more stable than doped ones. Various solid-state reaction kinetics, i.e., activation energy (E _a), frequency factor (Z), and entropy (ΔS*) was calculated out to find the mechanism of thermal decomposition at different stages for pure and cadmium doped barium phosphate.     

Spectral, optical, and thermal studies of pure and Zn(II)-doped l-histidine hydrochloride monohydrate (LHHC) crystals

The influence of doping the transition metal Zn(II) on the growth, spectral, optical, and thermal properties of l-histidine hydrochloride monohydrate (LHHC) crystals grown by slow solvent evaporation method has been investigated. Structural characterizations of the grown crystals were carried out by single crystal X-ray diffraction analysis and it shows slight structural changes as a result of doping. The FT-IR spectral study reveals the presence of various functional groups and confirms the slight distortion of the structure of the crystals due to doping. The energy dispersive X-ray analysis reveals the incorporation of Zn(II) in the crystalline matrix of LHHC crystal. The UV?CVis spectral study was carried out to analyze the optical transmittance of the grown crystals and found that the transmittance is very high in the visible and UV regions for both pure and doped crystals. The second harmonic generation (SHG) for the grown crystals was confirmed by Nd:YAG laser. The scanning electron microscopy reveals the presence of defect centers and crystal voids. The thermal stability and purity of the grown crystals were analyzed by thermogravimetry, differential thermal analysis, and differential scanning calorimetry techniques.     

Crystal growth and characterization of potassium(I)-doped tetrakis(thiourea)nickel(II) chloride

The influence of alkali metal potassium(I)-doping on the properties of tetrakis(thiourea)nickel(II) chloride crystals has been investigated. The variation in the intensity observed in powder X-ray diffraction (XRD) of doped specimen and slight shifts in vibrational frequencies confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the alkali metal are observed by scanning electron microscopy. The incorporation of K(I)- into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The crystal is further characterized by UV–Vis and Kurtz powder technique.     

Effect of alkali metal doping on the properties and crystalline perfection of bis(thiourea)zinc(II) chloride crystals

The influence of sodium doping on the properties of bis(thiourea)zinc(II) chloride crystals has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies confirm the lattice stress as a result of doping. The incorporation of Na(I) into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Surface morphological changes due to doping of the alkali metal are observed by scanning electron microscopy. The TG?CDTA studies reveal the purity of the material and no decomposition is observed up to the melting point. The high resolution X-ray diffraction studies reveal that the crystalline quality is improved considerably by doping with alkali metal. High transmittance is observed and cut off ?? is ~270?nm.     

Thermodynamic analysis of pure and impurity doped pentaerythritol tetranitrate crystals grown at room temperature

Pentaerythritol tetranitrate (PETN) powders are used to initiate other explosives. During long-term storage, changes in powder properties can cause changes in the initiation performance. Changes in the morphology and surface area of aging powders are observed due to sublimation and growth of PETN crystals through coarsening mechanisms, (e.g. Ostwald ripening, sintering, etc.). In order to alleviate the sublimation of PETN crystals under service conditions, stabilization methods such as thermal cycling and doping with certain impurities during or after the crystallization of PETN have been proposed. In this report we present our work on the effect of impurities on the morphology and activation energy of the PETN crystals. The pure and impurity doped crystals of PETN were grown from supersaturated acetone solution by solvent evaporation technique at room temperature. The difference in the morphology of the impurity-doped PETN crystal compared to pure crystal was examined by optical microscopy. The changes in the activation energies and the evaporation rates are determined by thermogravimetry (TG). Our activation energies of evaporation agree with earlier reported enthalpies of vaporization. The morphology and activation energy of PETN crystals doped with Ca, Na, and Fe cations are similar to that for pure PETN crystal, whereas the Zn-ion-doped PETN crystals have different morphology and decreased activation energy.     

Optical,piezoelectric and mechanical properties of xylenol orange doped ADP single crystals for NLO applications

Single crystals of pure and xylenol orange (XO; C₃₁H₃₂N₂O₁₃S) dye doped (0.01, 0.05 and 0.1 mol%) ammonium dihydrogen phosphate (ADP; NH₄H₂PO₄) were grown by slow evaporation method with the vision to improve the properties of pure ammonium dihydrogen phosphate crystal. The theoretical morphology of the grown crystals was drawn using Bravais–Friedel–Donnay–Harker (BFDH) law. The selective nature of xylenol orange dye to selectively stain the particular growth sectors of ADP crystal was studied. The structural analysis of as grown crystals was carried out using powder XRD study. The identification of the functional groups present in the ADP material was done using Fourier transform infrared (FTIR) spectroscopy. The linear optical study on pure and dye doped crystals was carried out using UV–vis–NIR spectroscopy. The optical band gap, extinction coefficient, refractive index and optical conductivity were calculated using the transmittance spectra for all the samples. In photoluminescence studies, the blue emission intensity got quenched and an orange emission at 597 nm was seen as a result of XO doping. The thermal stability and decomposition temperature of ADP crystal were found to decrease as an effect of dye doping. The piezoelectric charge coefficient, SHG conversion efficiency, mechanical strength and wettability were also enhanced as a result of XO dye doping.     

Effect of NaCl and KCl doping on the growth of sulphamic acid crystals

The nonlinear optical single crystals of doped sulphamic acid (SA) were grown from aqueous solution by doping with NaCl and KCl using slow evaporation method. Powder X-ray diffraction studies confirm that the grown crystals belong to orthorhombic system. The density and melting point measurements of the grown crystals were determined by floatation technique and capillary tube method, respectively. The range of optical transmittance was ascertained by recording the UV–Vis–NIR spectrum. Atomic absorption study reveals the presence of dopants in the doped crystals. The thermal analyses indicated that the doped SA crystals are more stable than pure crystals. The Vicker's microhardness studies revealed that the dopants increased the hardness of the crystals. SHG efficiency studies of the crystals are found to be increased in the presence of NaCl and KCl dopants.     

The effect of nitric acid (HNO3) on growth,spectral, thermal and dielectric properties of triglycine sulphate (TGS) crystal

The effect of nitric acid (HNO₃) addition on the growth of triglycine sulphate (TGS) crystal has been studied from the aqueous solution for various concentrations of nitric acid. Significant changes in the crystal size and morphology have been observed in all the grown samples. Single crystal and powder X-ray diffraction analyses confirm the structure and cell parameter values of pure and HNO₃ doped TGS crystals. FT-Raman and FTIR spectra confirm the characteristics absorption bands of pure and HNO₃ doped TGS crystals. The composition of TGS crystals have been confirmed by CHNS analysis. Physical properties such as thermal, dielectric and mechanical studies have been performed for the pure and HNO₃ doped TGS crystals. The dielectric constants of the crystals have been studied as a function of frequency. The results suggest that the HNO₃ is doped into TGS crystal and that the doping increases its dielectric constant.     

Structural, spectral, optical and dielectric properties of copper and glycine doped LAHCl single crystals

Cu2+ and glycine doped L-arginine monohydrochloride monohydrate (LAHCl) single crystals were grown by slow solvent evaporation technique. The grown single crystals were confirmed by X-ray diffraction study and the interaction of dopants with LAHCl molecule was identified in Fourier transform infrared spectra. The crystalline perfection of pure and doped crystals was analyzed by high resolution X-ray diffraction studies. Vickers microhardness and UV-visible spectroscopy were carried out respectively to study the mechanical stability and optical transmittance of pure and doped LAHCl single crystals. He-Ne laser of wavelength 632.8 nm was used to measure refractive index and birefringence of grown crystals. The second harmonic generation efficiency was also measured for pure and doped LAHCl single crystals using Nd:YAG laser.     

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.     

Synthesis and Characterization of SnO2 Nanopowder Prepared by Precipitation Method

Tetragonal SnO₂ nanopowder of the range ～8 nm has been successfully synthesized by precipitation method. The prepared powder was characterized by thermogravimetry analysis (TGA), x-ray diffraction (XRD), transmission electron microscopy (TEM), Infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), and room temperature photoluminescence (PL) spectroscopy. Experimental results show that the prepared powder was phase pure SnO₂ of tetragonal rutile structure without any impurities. The optical band gap was determined to be 4.26 eV, using diffuse reflectance technique with the aid of Kubelka-Munk relation. The blue shift of the band gap was attributed to the quantum size confinement effect.     

Effect of s-, p-, d-, and f-block elements on the structure and properties of ammonium dihydrogen phosphate crystals

The influence of the s-, p-, d-, and f-block elements (Cs, Sb, Pd, and Ce) doping on the properties of ammonium dihydrogen phosphate (ADP) crystals has been described. Incorporation of small quantity of dopants into the crystalline matrix is well confirmed by energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma (ICP) techniques. The reduction in the intensity observed in powder X-ray diffraction (XRD) of doped specimens and slight shifts in vibrational frequencies confirm the lattice stress. Surface morphological changes due to doping of metals are observed by scanning electron microscopy (SEM). The differential scanning calorimetry (DSC) curves show only a slight variation in endothermic peak temperatures. The sharpness of the DSC peaks shows the good degree of crystallinity of the material. The cell parameters have been determined using single crystal XRD analysis of pure ADP and ADP:Cs/ADP:Sb/ADP:Pd/ADP:Ce specimens. The influence of metals on the second harmonic generation (SHG) efficiency is also investigated.     

Synthesis and characterisation of alkaline earth-iron(III) double hydroxides

Double hydroxides containing alkaline earth and iron(III) ions were synthesised by the co-precipitation method. The solid materials obtained were characterised by a range of instrumental methods (powder X-ray diffractometry, thermogravimetry, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, elemental maps, and infrared spectroscopy). It was found that the Ca(II)Fe(III), Mg(II)Fe(III), and Ba(II)Fe(III) double hydroxides had layered structures, while Sr(II)Fe(III) had not. The optimum conditions for synthesis of Ca(II)Fe(III)-layered double hydroxides (materials to be used in further studies) were also elaborated.     

Synthesis and Characterization of PANI/ZnO Nanocomposites

This paper presents our results on the successful fabrication of HCl‐doped polyaniline (PANI)/ZnO nanocomposites via an electrochemical synthesis route. Different weight percents of ZnO nanoparticles were uniformly dispersed in the PANI matrix. The interaction between the dispersed ZnO nanoparticle and PANI was studied using X‐ray diffraction, ultraviolet–visible absorption spectroscopy, photoluminescence (PL) spectroscopy, X‐ray photoelectron spectroscopy, atomic force microscopy, thermogravimetry, and transmission electron microscopy. It is shown that the doping state of the PANI/ZnO nanocomposite is highly improved as compared to that of PANI. The dispersed PANI/ZnO nanocomposites exhibit enhanced PL behavior and thermal stability.     

稀土Ce掺杂对ZnO结构和光催化性能的影响

采用共沉淀-焙烧法合成了一系列不同含量的稀土Ce掺杂的ZnO光催化剂. 利用傅里叶变换红外(FT-IR)光谱、粉末X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见(UV-Vis)光谱、光致发光(PL)谱等技术对所制备的光催化剂进行了系列表征. 以酸性橙II脱色降解为模型反应, 考察了掺杂不同含量的铈及不同焙烧温度对ZnO的物理结构和光催化脱色性能的影响. 结果表明: 掺入质量分数(w)为2%的铈可以明显改善氧化锌表面状态, 有利于产生更多的表面羟基; 同时可以抑制光生电子与光生空穴(e^-/h⁺)的复合, 显著提高光催化脱色活性和光催化稳定性; 焙烧温度对光催化剂的晶体结构、表面性能和光催化活性产生较大影响, 500 °C的焙烧处理使样品的结晶度较高, 同时催化剂颗粒粒径较细, 表面具有丰富的羟基. 但过高的焙烧温度(600-800 °C)将导致催化剂的物理结构发生恶化, 降低光催化性能.     

稀土Ce掺杂对ZnO结构和光催化性能的影响

采用共沉淀-焙烧法合成了一系列不同含量的稀土Ce掺杂的ZnO光催化剂. 利用傅里叶变换红外(FT-IR)光谱、粉末X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见(UV-Vis)光谱、光致发光(PL)谱等技术对所制备的光催化剂进行了系列表征. 以酸性橙II脱色降解为模型反应, 考察了掺杂不同含量的铈及不同焙烧温度对ZnO的物理结构和光催化脱色性能的影响. 结果表明: 掺入质量分数(w)为2%的铈可以明显改善氧化锌表面状态, 有利于产生更多的表面羟基; 同时可以抑制光生电子与光生空穴(e^-/h⁺)的复合, 显著提高光催化脱色活性和光催化稳定性; 焙烧温度对光催化剂的晶体结构、表面性能和光催化活性产生较大影响, 500 °C的焙烧处理使样品的结晶度较高, 同时催化剂颗粒粒径较细, 表面具有丰富的羟基. 但过高的焙烧温度(600-800 °C)将导致催化剂的物理结构发生恶化, 降低光催化性能.     

Aluminium-doped LiFePO4 single crystals. Part I. Growth, characterization and total conductivity

Single crystals of Al-doped LiFePO4 (1% Al) were grown by an optical floating zone technique. After cleaving from the as-grown ingot they exhibited a blackish-green color. The grown crystals have been characterized by the Laue X-ray technique, single-crystal and powder X-ray diffraction. Phase composition has been determined by chemical analysis to be Li0.985+/-0.009Fe0.984+/-0.12Al0.0126PO3.993+/-0.06. Secondary ion beam spectroscopy (SIMS) indicates a homogeneous distribution of doped Al in the single crystal block. The total conductivities are shown to be electronic conductivities and have been measured along different directions with the help of the cell Ti/LiFe(Al)PO4/Ti. The samples exhibit effectively two-dimensional electronic conductivities along b- and c-directions similar as in pure LiFePO4. This decrease of conductivity on Al-doping compared with undoped crystals is in agreement with our previous conclusion of p-type conductivity of LiFePO4. Unlike nominally pure material not only the association of holes with lithium vacancies plays an important role but also purely ionic association.     

醇热法合成单晶银纳米线及其表征

以硝酸银为前驱物, 聚乙烯醇缩丁醛(PVB)为结构导向剂, 通过醇热法, 反应温度为140 ℃, 反应时间为24 h的条件下制备了银纳米线. 采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、热重分析(TG)、红外光谱(FT-IR)和激光拉曼光谱(Raman)等手段对产物进行了系统表征, 结果表明: 所得银纳米线具有面心立方结构, 沿着(111)晶面生长, 具有单晶结构; 考察了反应温度和时间对产物形貌的影响, 结果表明: 反应温度和时间在形成银纳米线的过程中起着关键的作用; 银纳米线具有较强的表面增强拉曼散射效应; 同时提出了银纳米线可能的晶化机理.