SEM/EDX microanalysis of a Na2OCdOSiO2 glass-ceramic containing sulphur

The formation or separation on cooling of a double cadmium-sodium sulfate CdSO₄·3Na₂SO₄ in a glass from the Na₂O-Al₂O₃-CdO-SiO₂ system has been detected by energy dispersive X-ray microanalysis (EDX) in a scanning electron microscope. The existence of prismatic and holed crystals of sulfate grown from the original glass is discussed.     

Investigating optical,electrical, and mechanical traits of thiourea admixtured KDP single crystals to explore NLO device applications

The 0.5 and 1 mol% thiourea “mixed” potassium dihydrogen phosphate (KDP) crystals have been developed by conventional slow solution evaporation method. The crystallographic parameters of grown crystals have been determined by employing single crystal X-ray diffraction technique. The functional groups of grown crystals were successfully identified by means of FTIR spectral analysis. The optical transmittance is 79%, 84%, and 89% for KDP, 0.5 mol thiourea mixed KDP, and 1 mol thiourea mixed KDP crystal. The energy band gap (E_g) of KDP, 0.5 mol thiourea mixed KDP, and 1 mol thiourea mixed KDP crystal is 3.71 eV, 3.61 eV, and 3.75 eV, respectively. The Kurtz–Perry test has been employed to determine the SHG efficiency and SHG efficiency of 0.5 and 1 mol thiourea mixed KDP crystal is 2.09 and 2.22 times superior to KDP crystal. Effect of thiourea mixing on hardness properties of KDP crystal have been scrutinized using the Vickers microhardness studies. The frequency dependent dielectric behavior of grown crystals has been analyzed at room temperature.

     

Crystal growth and transport properties of α- and γ-phase NaxCoO2

The Na_xCoO₂ single crystals with γ- and α-phase structure were grown by an electro-crystallization of high temperature solution (EHTS) method. X-ray diffraction studies showed that γ-phase Na_xCoO₂ crystals were grown from a flux of pure NaOH, and α-phase Na_xCoO₂ crystals were grown from a mixed flux of NaOH with a small amount of SrCO₃. The in-plane electrical resistivity of γ-phase Na_xCoO₂ decreases with decreasing temperature (T), exhibiting the metal-like properties, while that of α-phase Na_xCoO₂ increases with decreasing temperature, exhibiting the semiconductor-like properties. The thermoelectric power S(T) at 300 K is 80 μV/K and 30 μV/K for γ- and α-phase Na_xCoO₂, respectively, and both decrease with decreasing temperature. R_H of γ-phase Na_xCoO₂ shows anomalous temperature dependence.     

Effect of rotation of feed and seed rods on the quality of Na0.75CoO2 single crystal grown by traveling solvent floating zone method

High purity Na_0.75CoO₂ single crystals have been grown by floating zone method. We found the rotation of feed and seed rods play a crucial role in growing high quality single crystal. Systematic investigations suggest the occurrence of a phase separation at microscopic level, such as the separation into Na-rich and Na-poor domains during the growth, and formation of impurity phase(s) depending on growth conditions. Na_xCoO₂ (x = 0.30, 0.60) crystals have been prepared by sodium deintercalation from Na_0.75CoO₂. Powder X-ray and energy dispersive X-ray analyses have confirmed the phase purity and homogeneity of the samples. Magnetic susceptibility measurements of x = 0.60 and 0.75 crystals indicate a bulk phase transition at 22 K and an anomaly around 339 K and 334 K respectively which are attributed to structural transition. In addition some unique features related to Na_0.60CoO₂ were observed.     

X-ray Diffraction Study of the Structure and Defect System of Nominally Pure and Er<Superscript>3+</Superscript>- and Ce<Superscript>3+</Superscript>-Activated (Na<Subscript>0.5</Subscript>La<Subscript>0.5</Subscript>)MoO<Subscript>4</Subscript> Crystals

Nominally pure and activated (Er³⁺ and Er³⁺ + Ce³⁺) sodium lanthanum molybdate single crystals grown by the Czochralski technique from the (Na_0.5La_0.5)MoO₄ melt in different environments and then oxidized in air at 100°C are characterized in detail by x-ray diffraction (lattice parameters and structure refinement by the Rietveld method and single-crystal techniques). The results confirm that (Na_0.5La_0.5)MoO₄ crystallizes in a tetragonal scheelite structure (sp. gr. I₁/a). The crystals (especially unannealed crystals grown in neutral atmosphere) are shown to contain oxygen vacancies. In addition, some of the samples contain Mo vacancies. The Er³⁺ distribution over some of the activated crystals is highly inhomogeneous. As a result, the crystals contain Er-enriched zones with a distorted scheelite structure.     

Relaxor properties of single crystals of Na1/2Bi1/2TiO3-KTaO3 solid solutions

Single crystals of Na_1/2Bi_1/2TiO₃-KTaO₃ (NBT-KT) solid solutions have been grown for the first time. The elemental composition of as-grown single crystals determined by X-ray diffraction corresponds to 0.81 NBT-0.19 KT. Measurements of the temperature dependences of dielectric characteristics showed that the obtained NBT-KT crystals possess clearly pronounced relaxor properties.     

Synthesis, structure, growth and physical properties of a novel organic NLO crystal: 1,3-Dimethylurea dimethylammonium picrate

A novel noncentrosymmetric crystal was prepared from 1,3-dimethylurea dimethylammonium picrate, C₁₁H₁₈N₆O₈ (DMUP), which was designed for second harmonic generation. DMUP crystals exist in noncentro symmetric space group Cmc2₁ with unit cell dimensions a = 14.288(4) Å, b = 17.023(5) Å, c = 6.8268(13) Å, α = β = γ = 90° and volume = 1660.5(8) Å³. The crystal structure of DMUP has been determined using single crystal X-ray diffraction studies. The single crystals of DMUP were successfully grown by the slow evaporation method with dimensions 10 mm × 4 mm × 3 mm using dimethylformamide as solvent. The structural perfection of the grown crystals has been analysed by High-resolution X-ray diffraction (HRXRD) rocking curve measurements. Powder test with Neodymium-doped Yttrium aluminum garnet (Nd:YAG) laser radiation shows a high second harmonic generation (SHG). The laser induced surface damage threshold for the grown crystal was measured using Nd:YAG laser.     

Study of pure and l-tartaric acid doped ammonium dihydrogen phosphate single crystals: A novel nonlinear optical non-centrosymmetric crystal

Single crystals of pure and l-tartaric acid (LTA) C₄H₆O₆ doped ammonium dihydrogen phosphate (ADP) (NH₄) H₂PO₄ were grown by slow evaporation solution technique (SEST) at ambient conditions. Powder X-ray diffraction (PXRD) analysis was carried out to confirm the crystal structure and no additional phase was observed due to doping except a systematic variation in peak intensities. Fourier transform infrared spectral analysis was done to examine the presence of various functional groups in the grown crystals. UV–VIS–NIR spectroscopic analysis was carried out to see the change in optical transparency of pure ADP and crystals due to LTA with different doping concentrations. Second harmonic generation (SHG) efficiency measurement was done to examine the enhancement in the nonlinear optical characteristics of the grown crystals. The effect of LTA dopant on crystal morphology, thermal and mechanical properties of ADP have also been presented in this paper. The above studies reveal the effect of incorporation of LTA into the lattice of ADP crystals.     

Growth of gallium orthophosphate single crystals in acidic hydrothermal solutions

The hydrothermal growth of GaPO₄ single crystals has been studied in several solutions. Among many solutions, H₃PO₄, HCl and H₂SO₄ solutions were found to be effective solvents for the growth of GaPO₄ single crystals. Single crystals have been hydrothermally grown at temperatures over the range 210 to 290 °C in these solutions with seed crystals. HCl solution was found to be the most effective solvent in which to grow large single crystals. Morphologies of crystals grown at temperatures below 200 °C tended to be bounded by small major rhombohedral (1 0 ˉ1 1) faces. In the temperature range from 210 to 430°C, the crystals have morphologies bounded by prism (1 0 ˉ1 0), small major rhombohedral (1 0 ˉ1 1) and minor rhombohedral (0 1 ˉ1 1) faces, and grew with well developed basal (0 0 0 1) faces with increase in the growth temperature. Single crystals of GaPO₄ with lower dislocation density have been hydrothermally grown at 210 to 290°C in 3m H₃PO₄ solution.     

Preparation and characterization of some single,mixed and doped crystals and instrumentation aspects

The preparation and characterization (salient ones) of KAl (SO₄)₂. 12H₂O, KCr (SO₄)₂·12H₂O, mixed crystals of both with 10 to 90% of each component, mixed crystals of CsCl with CuCl₂, doped crystals of KBr with K₃FeCN₆, mixed crystals (NH₄)₂SO₄ with CuSO₄ or NiSO₄, NaCl with growth improver Pb⁺², Mn⁺², metallic crystals of Zn, Bi, ionic crystals of alkali halides with Pb⁺², or Cd⁺², etc. are presented. Instrumentation aspects of a rotary crystallizer, a homogeniser, an ingot release mechanism and a zone refiner are shown.     

Substitution du tungstene par le tantale dans les bronzes de tungstene NaxTayW1−yO3

In order to study the modification of the transport properties of Na_xWO₃ by substitution in the WO₃ sublattice, single crystals of tantalum-substituted tungsten bronzes of formula Na_xTa_yW_1?yO₃ have been grown by electrolytic reduction of fused Na₂WO₄WO₃Ta₂O₅ mixtures. The lattice constant of their cubic perovskite like structure increases with Ta content. Electric conductivity measurements on Na_xTa_yW_1?yO₃ single crystals characterize a metal-non metal transition when x-y, i.e. the number of d electrons, decreases. This transition seems to be of Anderson type.     

A study on the <Emphasis Type="SmallCaps">l</Emphasis>-lysine-iodic acid: semi organic non linear optical single crystals for electro-optic applications

Non linear optical single crystals of l-lysine-iodic acid (LLI) of dimensions upto 24?×?14?×?5 mm³ have been grown successfully by slow evaporation technique from aqueous solution. The crystal structure of the grown material was solved by single crystal X-ray diffraction analysis and it was found that the LLI crystal belongs to monocinic system with space group P2₁. Functional groups of the grown crystal were identified by Fourier Transform Infrared (FTIR) spectral analysis. The UV–Vis spectral analysis was carried out to measure the transparent range of the LLI crystal which is nearly 85% and the band gap energy is found to be 5.51 eV. Thermal stability and decomposition temperature of LLI crystal was found by means of TGA and DTA analyses. The mechanical behavior of the grown crystal has been employed using Vicker’s micro hardness technique. The Second Harmonic Generation (SHG) efficiency of the crystal was investigated and it was found to be 3.2 times of KDP. The particle size dependent SHG studies of LLI crystals were performed using Nd:YAG laser. The laser damage threshold value of LLI crystal is found to be 8.54 GW/cm². Dielectric study indicates the reasonable dielectric constant and low dielectric loss of LLI crystal which are essential properties to develop optoelectronic devices. The ac and dc electrical conductivity measurements were carried out at various temperatures. Photoconductivity study exhibits the negative photoconductivity nature of the LLI crystal and the results are discussed for the first time.     

Crystallization and characterization of Na2(La,Me)Zr(PO4)3

Na₂(La, Me)Zr[PO₄]₃ (where Me=Co, Al, Cr) crystals have been grown by three methods: by chemical reaction; from highly concentrated phosphoric acid solutions; and by a hydrothermal technique. The advantages and disadvantages of each method to obtain these crystals have been discussed. Morphological, X-ray, chemical analysis and IR-spectral studies were performed on these crystals.     

Low-temperature synthesis of leucite crystals using kaolin

Synthesis of leucite crystals below 1000 °C using natural kaolin as the primary raw material was investigated. Spherical leucite crystals having a diameter of approximately 50 μm were prepared by heating a powder mixture of Al₂(SO₄)₃, kaolin and K₂SO₄ (in mass ratios of 3:3:15) at 900 °C for 3 h. Quartz, the main accessory phase in kaolin, and the amorphous metakaolin formed upon heating kaolin were found to be responsible for the decreased synthesis temperature.     

Investigation on (100) face of KDP crystal poisoned by MoO4 2? impurity

Potassium dihydrogen phosphate (KDP) single crystals doped with molybdate (MoO₄ ²⁻) were grown via the conventional temperature cooling and rapid growth methods, respectively. MoO₄ ²⁻ made KDP crystals tapering for conventional temperature cooling method. When KDP crystals were grown by rapid growth method, MoO₄ ²⁻ could induce liquid inclusions and simultaneous crystals. The measurement on growth rates indicated that MoO₄ ²⁻ broadened the dead zone and decreased the growth rate of (100) face of KDP crystals. The growth kinetic analysis in terms of two-dimensional nucleus and screw dislocation models implied that the energetic parameter γ/kT decreased with an increase of MoO₄ ²⁻ concentration. The influence of MoO₄ ²⁻ growth steps on (100) face of KDP crystal was observed through ex situ AFM technique. It gave evidence that MoO₄ ²⁻ could postpone the step bunching and make the step edge curving and knaggy to reduce the edge free energy, which was in agreement with the growth kinetics calculations. Additionally, the poisoned mechanism of MoO₄ ²⁻ and Fe³⁺ on step morphologies was detailed contrasted. The interaction process was discussed according to electro negativity analysis, which indicated MoO₄ ²⁻ (actually were HMoO₄ ⁻ and H₂MoO₄) could be absorbed onto (100) face through charge-assisted hydrogen bonds and caused more Mo element distributed in prismatic sector.     

Growth and characterization of pure and lithium doped strontium tartrate tetrahydrate crystals by solution-gel technique

The effect of lithium ion as dopant on the size and transparency of strontium tartrate tetrahydrate (SrC₄H₄O₆·4H₂O) crystals are presented in this paper. Growth of single crystals of undoped and lithium doped strontium tartrate tetrahydrate by controlled diffusion of strontium nitrate into the gel charged with tartaric acid at room temperature are narrated. The lithium ion enhances the size and transparency of the doped crystals. The crystal structure of the compound was confirmed by X-ray diffractometry and dopant concentration with ICP-atomic emission spectrometer system. Thermal decomposition of the grown crystals is investigated by TGA and DTA studies. The FTIR spectra of pure and doped crystals are recorded and analysed. Kurtz powder technique has been used to test SHG efficiency of the crystals.     

Synthesis and characterization of cuprous sulfide crystals with novel morphology

Cuprous sulfide (Cu_2−xS) crystals in different stoichiometries were synthesized by hydro- and solvo-thermal methods at 125 °C using Na₂S₂O₃ as sulfur source in pure water, mixed solvents of ethylenediamine (en) and water, and pure en, respectively. The products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersion spectrometer (EDS), transmission electron microscope (TEM) and selected area electronic diffraction (SAED). Owing to different sulfur sources, crystal structures and morphologies of cuprous sulfides were different from those developed by some former researchers. Novel twelve-fold symmetrical Cu₇S₄ single crystals were synthesized at an en/water volume ratio of 3:1, and they were built up by two layers of about 80-100 nm in thickness. Moreover, the possible growth process had been discussed based on the analyses of detailed configuration of the products.     

Synthesis,crystal growth and characterization of novel semiorganic nonlinear optical crystal: Dichlorobis(l-proline)zinc(II)

Single crystals of the semiorganic material, dichlorobis(l-proline)zinc(II) (DCBPZ), were grown from aqueous solution. The grown crystals were tested by single crystal X-ray diffraction, energy-dispersive spectrometry, FT-IR, UV–vis and TG–DTA. The structural prefection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The dielectric and mechanical behavior of the specimen was also studied. The SHG efficiency of DCBPZ is three times greater than that of KDP. Measuring transmittance of DCBPZ permitted the calculation of the refractive index n, the extinction coefficient K and both the real ?_r and imaginary ?_i components of the dielectric constant as functions of photon energy. The optical band gap of DCBPZ is 4.8 eV.     

Crystal growth of sodium iron titanium bronze compounds under hydrothermal conditions

Single crystals of four types of oxides consisting of sodium iron and titanium were grown hydrothermally under reduced conditions starting with a mixture of TiO₂ (rutile) and metallic Fe powder in the ratio 5:1 (weight basis) at 650°C and 1000kg/cm² in 10m NaOH solution for different durations. Formation of single crystals having an orthorhombic cell was observed after one week. In longer runs under the same conditions the initial phase undergoes transformation to form crystals having hexagonal and orthorhombic cells and finally to monoclinic freaudenbergite (Na₂O·Fe₂O₃·7TiO₂). From Mössbauer and EPMA data, the common chemical formula for these new phases can be written as (Na_xFe²⁺_y) · [Ti_pFe²⁺_qFe_r³⁺O_2?δ]_n.     

Facile and rapid synthesis of multiferroic TbMnO3 single crystalline

The pure single phase of multiferroic material TbMnO₃ powders were successfully synthesized by one-step molten salt synthesis (MSS) method in the NaCl–Na₂SO₄ eutectic salts at the temperature as low as 800 °C for 1 h. The temperature of synthesized high purity TbMnO₃ is limited in a very narrow range. Prolonging the sintering time will not have an effect on the purity of samples, and either lower or higher salt concentration is not conducive to form pure TbMnO₃. The obtained TbMnO₃ was indexed to an orthorhombically distorted perovskite phase. The as-prepared crystals exhibit uniform and regular rhombic-like morphology with an average size of about 2 μm in edge length and 1–2 μm in thickness. The elements Mn and Tb in TbMnO₃ exist dominantly as Mn³⁺ and Tb³⁺, respectively. The magnetic measurements of the TbMnO₃ powders exhibit antiferromagnetism. Because of the simplicity and generalizability of the MSS method, it is reasonable to expect that the MSS method could also be exploited in future works which involves the nanoscale investigation of ferroelectric, ferromagnetic and multiferroic materials.