Crystal growth and properties of the AgIn5S8 compound

AgIn₅S₈ single crystals were prepared by vapour transport. An improved procedure for a good supersaturation control was obtained by raising source temperature while maintaining growth temperature at a fixed value. Crystals up to 10×5×5 mm³ could be grown. Using X-ray measurements previously reported f.c.c. structure for powdered samples was confirmed. A direct bandgap of about 1.7eV and n-type conductivity was found. Carrier concentration and electron mobility are reported as varying with temperature in the range 100–350°K.     

Vapor growth of hexagonal GeO2 needle crystals

Needle crystals of haxagonal GeO₂ were grown at 750–900°C by the oxidation of GeO vapor which was generated by the reduction of GeO₂ with graphite. The largest crystals were grown at higher temperature, and had a maximum size of 10 μm diameter and 6 mm length after growth at 900°C for 5 hours. The growth direction of the crystals was parallel to the a-axis.     

Preparation and characterization of Cd.95Mn.05Se single crystals

Homogeneous crystals of Cd_.95Mn_.05Se of high optical quality have been grown by a modified Bridgman method. Magnetic susceptibility measurements verify the uniform distribution of Mn(II) obtained after annealing at 600°C.Crystals grown in the presence of 5 atomic percent excess selenium showed high resistivity; the addition of 1 mg iodine to a 10 g charge resulted in n-type conductivity and a room-temperature carrier concentration of 2.9 × 10¹⁶ cm^?3. The Hall mobility of these crystals was approximately 290 cm² V^?1 sec^?1.     

Crystal growth and characterization of In23PS3

Crystals of $\text{In}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{PS}{}_3$ were grown by chemical vapor transport of the elements from a charge zone maintained at 630°C. and a growth zone at 560°C. The crystals were characterized by chemical, x-ray, and densitometric techniques. $\text{In}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{PS}{}_3$ is structurally related to the M^IIPS₃ thiophosphides. The compound is an insulator and has an optical absorption edge of 3.1(1) e.V.     

Elaboration et caracterisation de monocristaux de V2O3 par transport en phase vapeur

Single crystals of V₂O₃ are obtained by HCl or TeCl₄ chemical transport method in sealed quartz tubes with temperature gradients of 1050–930°C and 990–900°C respectively. The hexagonal prims are 5 mm long and 1 or 2 mm wide. Both kinds of crystals are characterized by sharp insulator-metal transition at 156 and 137 K respectively, they present a large hysteresis. The sharp decrease in resistivity with increasing temperature is of the order of 10⁸ at the transition.     

Dielectric and photoconducting properties of Ga2Te3 and In2Te3 crystals

Single crystals of defect III–VI semiconductors Ga₂Te₃ and In₂Te₃ have been grown by the Bridgman method. Capacitance vs frequency measurements have been carried out from which the low frequency dielectric constants ?₅ have been determined to be 10.95 ± 0.26 and 12.3 ± 0.13 respectively. These values are compared with the high-frequency dielectric constants ?₆₀ calculated from the Phillips' model. Dark conductivity and photoconductivity have been studied as a function of annealing upto 210°C, maxinum photosensitivity being obtained for both crystals for T_anneal = 80°C. This behaviour has been related to lattice ordering through x-ray diffraction studies. Measurements of photo conductive gain indicate carrier life-times of 2 × 10^?4s and 5 × 10^?4s respectively at room-temperature.     

Vapour growth and crystal data of the thio(seleno)-hypodiphosphates Sn2P2S6, Sn2P2Se6, Pb2P2Se6 and their mixed crystals

Single crystals (monoclinic polyhedra up to 5×5×5 mm³) of the thio(seleno)-hypodiphosphates Sn₂P₂S₆ (yellowish-brown), Sn₂P₂Se₆ (black), Pb₂P₂S₆ (yellow) and Pb₂P₂Se₆ (dark-red) have been grown by vapour transport with iodine. The space group of Sn₂P₂S₆ is Pc, that of the other compounds P2₁/c. All four compounds are completely miscible. Already small replacements of Sn by Pb (around 10 mole %) in Sn₂P₂S₆ change the space group to P2₁/c. The pure as well as the 1:1 mixed-anion and mixed cation compounds were characterized by x-ray and thermal analysis.     

Single crystals of In2Te5

Single crystals of semiconducting compound In₂Te₅ were grown by chemical transport employing iodine as a transport agent. The crystals had a plate-like habit with the [100] direction perpendicular to the flat surface of the platelets. Nominal dimensions are 10 × 1 × 0.05 mm. In₂Te₅ has a monoclinic structure with dimensions of the base centered cell: $\text{a}\text{= 13.47}\text{A}\text{?}$, $\text{b}\text{= 16.51}\text{A}\text{?}$, $\text{c}\text{= 4.365}\text{A}\text{?}$, β = 92°5′. The space group is $\text{C}{}_{\mathrm{<mtext>2</mtext><mtext>c</mtext>}}$. Pycnometric density is 5.96 g/cm³. The single crystals were all p-type. The conductivity, thermoelectric power and hardness were about 10^?5Ω^?1cm^?1, 650 mkV/°C, and 30 kg/mm², respectively. The minimum energy gap is 1.26 eV.     

Growth and physical properties of ZnGeAs2

Single-phase poly crystalline chalcopyrite-structure ZnGeAs₂ ingots with an average grain size of 70 μm have been grown using a modified vertical Bridgman apparatus. The melting point of the compound was determined by differential thermal analysis (DTA) to be 860°C and corrected X-ray diffraction (XRD) peak positions were obtained. The crystals were p type with a room-temperature carrier concentration of 1.1 × 10¹⁹ cm^?3 and a corresponding mobility of 15 cm²/V s. A possible chalcopyrite-to-sphalerite phase transition, reported previously to occur to 812°C, was not observed either by DTA or by XRD of quenched samples.     

Epitaxial growth of MgAl2O4 spinel crystals by solid-state reaction of MgO crystal with molten Al metal

Single crystals of MgAl₂O₄ spinel have been prepared epitaxially by a solid-state reaction of MgO crystal with molten Al metal under vacuum of 10^?5≈10^?6 torr at 1000≈1100°C. The growth rate was estimated to be about 0.1≈0.2 mm/hour in this temperature range. The as-grown crystals were black and opaque with low crystallinity, which was improved by heating above 1350°C. Chemical analysis showed that the crystals were slightly contaminated with Mg metal which was easily oxidized above 900°C in air.     

Czochralski growth of Ba6Ti2Nb8O30

Ba₆Ti₂Nb₈O₃₀ (BTN) single crystals have been grown by the Czochralski method under a reducing atmosphere. Crystals grown in an oxidizing atmosphere were opaque polycrystals. It was found that BTN decomposes into several phases at temperatures above 1330°C. No congruent melt composition was found around stoichiometric composition in an oxygen or air atmosphere.     

V2S3: Structure and thermal stability

Vanadium sesquioxide, V₂O₃, has been considered as a potential desulfurization agent for hot coal gases. The proposed process is based on the conversion of V₂O₃ to V₂S₃ via reaction with H₂S. Prompted by conflicting information in the literature on the thermodynamic stability and crystal structure of the potential desulfurization product, V₂S₃ was synthesized; its thermal stability determined using thermogravimetric analysis; and its structure studied using x-ray diffraction. In a relatively inert atmosphere, V₂S₃ commences decomposition near 270°C; in oxygen, near 240°C; and in 10% hydrogen, near 325°C. Analysis of the x-ray diffraction data from both powder and crystals indicated a large hexagonal unit cell with a = 6.634(3), $\text{c}\text{= 22.49(4)}\text{A}\text{?}$.     

Vapour growth and structural characterization of the new indium bismuth sulphide halides InBi2S4Cl and InBi2S4Br

The title compounds were prepared for the first time, and ledge-shaped single crystals were grown by chemical vapour transport. InBi₂S₄Cl(Br) crystallizes in the space group $\text{C}\text{2}\text{m}$ with lattice parameters a = 12.383 (12.55), b = 3.899 (3.90), $\text{c}\text{= 8.514 (8.58)}\text{A}\text{?}$, and β = 115.30 (115.2)°; Z = 2. The crystal structure of InBi₂S₄Cl was determined from 816 independent reflexions and refined to R = 4.0%. The indium atoms occupy the center of distorted sulphur octahedra which are linked to chains running in y-direction. They are interconnected by bands of bismuth and chlorine atoms. Bismuth is irregularly surrounded by six sulphur and two chlorine atoms.     

Crystal growth and magnetic anisotropy of YTiO3

Single crystals of YTiO₃ were grown from the melt by the Czochralski technique from molybdenum crucibles under purified argon. YTiO₃ melts congruently at about 1965 ± 30°C. The largest crystals were a few mm on a side. Measurements of the magnetic moment of oriented single crystals at 4.2K reveal that the b- and c-axes are easy axes of magnetization while the a-axis is hard. The saturation magnetization in either of the easy directions is 0.84 ± .01 μ_B mole^?1.     

Hydrothermal recrystallization of Bi2WO6

The feasibility of growing single crystal Bi₂WO₆ by the hydrothermal method is reported. Single domain crystals (～1mm) were readily grown at 400°C, well below the disruptive high temperature phase transformation, from 2N aqueous KF solutions. Data is given for X-ray diffraction and hot-stage microscopy observations. The significance of preparing strain-free, single domain, highly acentric polar crystals for new device applications is discussed.     

Preparation and ionic conductivity of new B2S3-Li2S-LiI glasses

Glasses obtained in the B₂S₃-Li₂S-LiI system have been investigated. Ionic conductivity is higher than 10^?3Ω^?1cm^?1 at 25°C for LiI-rich glasses. The electrochemical stability range and chemical stability allow their use as solid electrolytes in solid state batteries.     

Preparation and some properties of materials in systems of the type MIMIIIS2MIMIIISe2 where MI = Cu,Ag and MIII = Al,Ga, In

Complete solid solution between sulfide chalcopyrites (M^IM^IIIS₂) and selenide chalcopyrites (M^IM^IIISe₂ where M^I = Cu, Ag and M^III = Al, Ga, In) has been shown to exist. Single crystals of compositions CuGaS_1.5Se_0.5, CuGaSSe, CuGaS_0.5Se_1.5, have been grown by vapor transport techniques. These materials have a non-centrosymmetric crystal structure and exhibit second harmonic generation. Approximate band gaps of the crystals were obtained from optical transmission measurements.     

Electrical properties of La2S3-doped calcium sulfide solid electrolyte

In order to consider the application of La₂S₃-doped calcium sulfide to a solid electrolyte for metal sulfide systems, its electrical properties have been investigated, based on a galvanic cell technique and conductivity measurements at various temperatures and sulfur pressures. The following cell was employed; Cu,Cu₂S |CaS (La₂S₃)| FeS, Fe. The values of the electromotive force obtained in this cell were roughly consistent with the theoretical ones. Based on conductivity measurements under various sulfur pressures at 700–900°C, the electrical conduction of La₂S₃-doped calcium sulfide was found to be ionic at sulfur pressures higher than 10^?6 atm and n-type semiconducting at lower sulfur pressures. The apparent activation energy obtained for the ionic conduction was 19.02 kcal/mol, which was reasonable for the ionic conduction through migration of a Ca²⁺ ion.     

Systeme Ga2S3FeS — Diagramme de phase — etude cristallographique

The system was studied by DTA, X-ray diffraction and in particular by the Guinier-Lenné method. Eight intermediate phases are described. 1) Three solid solutions in the Ga₂S₃ region : a) a wurtzite-type solid solution (T > 1000° C ; 0.05 < n < 0.23) (n = Fe $\text{at}\text{Fe}$ at+Ga at), b) a blende-type solid solution (700°C < T < 980°C ; 0.10 < n < 0.20) with many stacking faults, c) a non-stoichiometric hexagonal phase α'Ga₂S₃ type (T < 700°C, 0.07 < n < 0.12). 2) for n = 0.20 and T = 540°C a superstructure of orthorhombic wurtzite-like array FeGa₄S₇. 3) From n = 0.20 through n = 0.27, a non stoichiometric superstructure of tetragonal-like array has the CdGa₂S₄ type (600°C < T < 1030°C). 4) For n = 0.33, the FeGa₂S₄ has two forms depending from the temperature : a) a low temperature form is trigonal ; b) a high temperature form is orthorhombic type ZnAl₂S₄. Transition temperature is 1010°C. 5) For n = 0.50, Fe₂Ga₂S₅ polytypes : a) Fe₂Ga₂S₅α 1T type Mn₂Ga₂S₅ ; b) Fe₂Ga₂S₅ 2H ; c) Fe₂Ga₂S₅ 3R type Mn₂Al₂Se₅. A phase diagram is proposed.     

Synthesis, elaboration and characterization of the new material CuIn3S5 thin films

CuIn₃S₅ compound was prepared by direct reaction of high-purity elemental copper, indium and sulphur. CuIn₃S₅ thin films were prepared from powder by thermal evaporation under vacuum (10⁻⁶ mbar) onto glass substrates. The glass substrates were heated from 30 to 200 °C. The powder was characterized for their structural and compositional properties by using X-ray diffraction (XRD) and energy dispersive X-ray (EDAX). The XRD studies revealed that the powder exhibiting P-chalcopyrite structure. From the XRD data, we calculated the lattice parameters a and c. Then, the cation–anion bond lengths l _AC and l _BC are deduced. The films were characterized for their structural, compositional, morphological and optical properties by using XRD, EDAX, atomic force microscopy and optical measurement techniques (transmittance and reflectance). XRD analysis revealed that the films deposited at a room temperature (30 °C) are amorphous in nature, whereas those deposited on heated substrates (≥75 °C) were polycrystalline with a preferred orientation along (112) of the chalcopyrite phase. The surface morphological analysis revealed that the films grown at different substrate temperature had an average roughness between 1.1 and 4.8 nm. From the analysis of the transmission and reflection data, the values of direct and indirect band gap of the films were determined. We found that the optical band gap decreases when the substrate temperature increases.