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Showing papers in "Crystal Research and Technology in 1993"


Journal Article
TL;DR: In this paper, the early days of the Rietveld method are described, along with a retrospective view of its application in various areas of physics, such as X-ray and neutron analysis.
Abstract: Introduction to the Rietveld Method 1. The early days: a retrospective view 2. Mathematical aspects of Rietveld refinement 3. The flow of radiation in a polycrystalline material 4. Data collection strategies: fitting the experiment to the need 5. Background modelling in Rietveld analysis 6. Analytical profile fitting of X-ray powder diffraction profiles in Rietveld analysis 7. Crystal imperfection broadening and peak shape in the Rietveld method 8. Bragg reflection profile shape in X-ray powder diffraction patterns 9. Restraints and constraints in Rietveld refinement 10. Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources 11. Combined X-ray and neutron Rietveld refinement 12. Rietveld analysis programs Rietan and Premos and special applications 13. Position - constrained and unconstrained powder-pattern-decomposition methods 14. Ab initio structure solutions with powder diffraction data

3,162 citations


Journal ArticleDOI
TL;DR: In this article, the asymmetric unit of X-ray intensity data for a crystal is the same as that for the crystal forms { hkl} with the symmetry of its Laue group.
Abstract: and hexagonal lattices. Furthermore, the point group 3m in the hexagonal description is further subdivided into two casesone having the normal of the mirror planes in the [100] direction and the other one having the normal in the [210] direction. The Laue group 2/m is also subdivided into two cases with the b axis unique and with the c axis unique. Since the distribution of the X-ray intensity l(hkl) in reciprocal space shows the same symmetry as a general crystal form of the corresponding Laue class, the asymmetric unit of X-ray intensity data for a crystal is the same as that for the crystal forms { hkl} with the symmetry of its Laue group. Table 1 shows information on the 11 Laue groups (column 3). The crystal system is given in column 1, all corresponding noncentrosymmetric point groups are listed in column 2. Column 4 describes one asymmetric unit for the intensity data of each Laue group. Alternative possibilities are separated by dashed lines. The last column shows the fraction of reciprocal space belonging to one asymmetric unit.

110 citations


Journal ArticleDOI
TL;DR: In this paper, the growth of High-T c (HTP) and Low T c (LTP) phases upon lead substitution for bismuth has been analyzed using characterisation techniques like XRD, SEM, EDXA, d.c. resistance, and a.k.a. magnetic susceptibility.
Abstract: Superconducting samples of the composition Bi 2-x Pb x Ca 2 Sr 2 Cu 3 O y (x=0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) are prepared by co-decomposition of metal nitrates. DTA, TGA, density, and porosity studies have been performed on these samples. Characterisation techniques like XRD, SEM, EDXA, d.c. resistance, and a.c. magnetic susceptibility have been employed to study the growth of High-T c (HTP) and Low-T c (LTP) phases upon lead substitution For bismuth. Results have revealed the growth of HTP with increase in Pb conc. up to x=0.3. Further increase in Pb appears to result in the deterioration of HTP resulting in the formation of LTP and Ca 2 Pb 4 impurity phase

32 citations


Journal ArticleDOI
TL;DR: In this article, two types of spirals, viz. those having opposite orientation present on the same face and those present on opposite finished faces, are significantly discussed, and two different types of spiral structures are compared.
Abstract: Thin flakes of tin disulphide single crystals grown using direct vapour transport technique have been subjected to characterization to unfold their growth mechanism. Two types of spirals, viz. those having opposite orientation present on the same face and those present on the opposite finished faces are significantly discussed

28 citations


Journal ArticleDOI
TL;DR: In this article, the spin arrangement in mechanically activated zinc ferrite is connected with a redistribution of the cations in the close-packed anionic sublattice, and the degree of mechanically induced inversion as well as the exact coordinates of atoms and lattice parameters in non-activated and mechanically activated ZnFe2O4 were determined.
Abstract: The mechanically induced changes in structure and magnetic properties of zinc ferrite were investigated by using the Rietveld analysis and Mossbauer spectroscopy. The formation of the spin arrangement in mechanically activated zinc ferrite is connected with a redistribution of the cations in the close-packed anionic sublattice. On the basis of the Rietveld analysis the degree of mechanically induced inversion as well as the exact coordinates of atoms and lattice parameters in non-activated and mechanically activated ZnFe2O4 was determined. Es wurden die mechanisch induzierten Strukturanderungen und Eigenschaften vom Zinkferrit mittels der Analyse nach Rietveld und der Mossbauer-Spektroskopie untersucht. Das Enststehen der Spinanordnung in mechanisch aktiviertem Zinkferrit steht mit der Veranderung der Kationenanordnung in Zwischenraumen der dichten Kugelpackungen von Sauerstoffionen im Zusammenhang. Mit Hilfe der Rietveldschen Analyse wurden der mechanisch induzierte Inversionsgrad, die genauen Koordinaten von Atomen und Gitterparameter in nichtaktiviertem und mechanisch aktiviertem ZnFe2O4 bestimmt.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of pH and temperature of aqueous solution on hydration of MgO in a batch laboratory reactor was investigated and the experiments were carried out at the temperatures of 120 and 140 o C, pH of cool solution was changed from 10 to 13.
Abstract: The effect of pH and temperature of aqueous solution on hydration of MgO in a batch laboratory reactor was investigated The experiments were carried out at the temperatures of 120 and 140 o C, pH of cool solution was changed from 10 to 13 It was found that even a small amount of added base substance influences remarkably the size of Mg(OH) 2 crystals Increasing of pH of aqueous environment causes the decrease of the size of crystals The increase of the temperature increase dimensions (L 50 ) of crystals This effect is more important at higher alkalinity of the solution

27 citations


Journal ArticleDOI
TL;DR: A systematic review of different types of traditional averages for diffraction elastic constants in textured materials is given in this article, where a new type of average, which recently was suggested, is presented.
Abstract: A systematic review of different types of traditional averages for diffraction elastic constants in textured materials is given. In addition a new type of average, which recently was suggested, is presented. These averages are of vital importance for a correct interpretation of internal (e.g. residual) stress measurements. The theoretically predicted diffraction elastic constants are compared with the experimental ones for rolled steel samples; there exists good agreement between theory and experiment. On presente une revue systematique des moyennes traditionelles utilisees pour le calcul des constants elastiques de diffraction dans le cas des materiaux avec la texture cristalline. On presente aussi une nouvelle moyenne, recemment proposee. Ces moyennes sont tres importantes pour une interpretation correcte des mesures de contraintes internes (p.ex. contraintes residuelles). Les constants elastiques de diffraction calcules sont compares avec ceux mesurees pour l'acier lamine; l'accord est tres bon.

24 citations


Journal ArticleDOI
TL;DR: In this article, single crystals of potassium pentaborate were grown by the solution growth method and characterised by optical transmission spectrum, differential thermal analysis, and thermogravimetric analysis.
Abstract: Single crystals of potassium pentaborate were grown by the solution growth method. The grown crystals were characterised by optical transmission spectrum, differential thermal analysis, and thermogravimetric analysis. The coefficient of thermal expansion was also determined and the results discussed.

24 citations



Journal ArticleDOI
TL;DR: The history of the discovery of X-ray diffraction in crystals and its first sequels are reported; the life of M. v. Laue, the discoverer and founder of a first basic theory, and of P. P. Ewald, who contributed to the discovery and to later developments of the theory are shortly described.
Abstract: The history of the discovery of X-ray diffraction in crystals and its first sequels are reported; the life of M. v. Laue, the discoverer and founder of a first basic theory, and of P. P. Ewald, who contributed to the discovery and to later developments of the theory, are shortly described.

20 citations


Journal ArticleDOI
TL;DR: The composition of scales formed in multiple evaporator units at three Australian sugar mills have been determined using X-ray fluorescence (XRF), high performance liquid chromatography (HPLC), XRD, thermogravimetry/differential thermal analysis (TG/DTA) and other analytical methods as mentioned in this paper.
Abstract: The composition of scales formed in multiple evaporator units at three Australian sugar mills have been determined using X-ray fluorescence (XRF), high performance liquid chromatography (HPLC), X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA) and other analytical methods. The composition of the scales formed in each mill have been found to be significantly different and to depend on whether they originated from early or later stages of the evaporation process. Calcium oxalate (present as the di and monohydrate) was identified as a major component of the scales from one mill but was found to be only a minor component of the scales from the other two. The latter were shown to contain two or more forms of calcium phosphate as dominant phases. Amorphous or crystalline silica was found to be present in most of the scales examined.

Journal ArticleDOI
TL;DR: The X-ray crystal structure of the mononuclear manganese (II) complex containing saccharin and 1,10-phenanthroline, [Mn(Sacch 2 (o-Phen) 2 (H 2 O) 2 ] was reported in this article.
Abstract: The X-ray crystal structure of the mononuclear manganese(II) complex containing saccharin and 1,10-phenanthroline, [Mn(Sacch) 2 (o-Phen) 2 (H 2 O) 2 ].H 2 O, is reported. The manganese atom has a geometrical structure of hexa-coordinated distorted octahedron, saccharins interact with the central atom through water molecules

Journal ArticleDOI
TL;DR: In this article, it was shown that cyclohexylamine can be used for the synthesis of SAPO-35 with the levyne-like structure, and the number of acid sites (Bronstedt centres) was determined from the differential molar heat of chemisorption of NH3 to three per unit cell.
Abstract: The microporous aluminophosphate SAPO-35 with the levyne-like structure was prepared hitherto only with quinuclidine as templating agent. In this paper it is shown that also cyclohexylamine can be used for the synthesis of SAPO-35. The samples were characterized by X-ray diffraction, thermal analysis, adsorption isotherms, and micrographs. These investigations confirm the few data reported on SAPO-35 and give further informations. The number of acid sites (Bronstedt centres) was determined from the differential molar heat of chemisorption of NH3 to three per unit cell. Das mikroporose Alumophosphat SAPO-35 von einer Struktur, die der des Levyns ahnlich ist, wurde bisher nur mit Chinuclidin als Templat hergestellt. In dieser Arbeit wird gezeigt, das zur Synthese von SAPO-35 auch Cyclohexylamin verwendet werden kann. Die Proben wurden durch Rontgenbeugung, thermische Analyse, Adsorptionsisothermen und elektronenmikroskopische Bilder charakterisiert. Die Mesergebnisse bestatigen die wenigen in der Literatur veroffentlichten Daten von SAPO-35 und geben weitere Informationen. Die Anzahl der sauren Zentren (Bronstedt-Zentren) wurden durch kalorimetrische Messung der differentiellen molaren Adsorptionswarme von NH3 zu drei pro Elementarzelle ermittelt.

Journal ArticleDOI
TL;DR: In this paper, the lattice constants, particle size, lattice strain and Debye-Waller factors have been determined from the correlation between the strain and the effective DEW factor.
Abstract: Lattice strains have been produced in cadmium telluride by grinding for different durations. X-ray diffractograms have been obtained at different stages of grinding. The lattice constants, particle size, lattice strain and Debye-Waller factors have been determined. From the correlation between the strain and the effective Debye-Waller factor, the Debye-Waller factor for zero strain has been estimated.

Journal ArticleDOI
H. Neumann1
TL;DR: In this paper, the amplitude of the photoacoustic signal of a gas-coupled cell for thick semiconductor samples including the influence of multiple reflections of light within the sample was derived.
Abstract: Theoretical relations are derived for the amplitude of the photoacoustic signal of a gas-coupled cell for thick semiconductor samples including the influence of multiple reflections of light within the sample. It is shown that in the range of low absorption coefficients characteristic of impurity absorption spectra the sensitivity of the cell can be enhanced by using a highly reflecting metal as backing material. Numerical estimates for CuInSe2 are given to illustrate this effect. Theoretische Beziehungen fur die Amplitude des photoakustischen Signals einer gasgekoppelten Zelle werden fur dicke Halbleiterproben unter Berucksichtigung des Einflusses von Mehrfachreflexionen des Lichts innerhalb der Probe hergeleitet. Es wird gezeigt, das die Empfindlichkeit der Zelle im Bereich niedriger Absorptionskoeffizienten, wie sie fur Storstellenabsorptionsspektren charakteristisch sind, durch Verwendung eines stark reflektierenden Metalls als Ruckseitenmaterial erhoht werden kann. Zur Veranschaulichung des Effekts werden numerische Abschatzungen fur CuInSe2 angegeben.

Journal ArticleDOI
TL;DR: In this paper, the dielectric constant and loss tangent were determined as a function of temperature for β-BaB 2 O 4 or BBO and KB 5 O 8.4H 2 O or KB5.
Abstract: Single crystals of beta barium borate and potassium pentaborate (commonly known as β-BaB 2 O 4 or BBO and KB 5 O 8 .4H 2 O or KB5) were grown by high and low temperature solution growth methods, respectively. The dielectric constant and loss tangent were determined as a function of temperature. Frequency response of the dielectric constant and tan 6 have been studied over a frequency range of 0.1-100 kHz; it is found that both the dielectric constant and tan 6 decrease with increase in frequency for both crystals. The dielectric constant and tan 6 are found to increase with increase in temperature for both the crystals. Further, the dielectric constant and tan 6 measured on different orientations of the grown crystals reveal the anisotropic nature of the crystals

Journal ArticleDOI
TL;DR: Strontium tartrate tetrahydrate single crystals doped with nickel have been grown in silica gel and characterized by X-ray, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and etching technique as mentioned in this paper.
Abstract: Strontium tartrate tetrahydrate single crystals doped with nickel have been grown in silica gel. The grown crystals have been characterized by X-ray, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and etching technique.

Journal ArticleDOI
S. K. Lilov1
TL;DR: In this article, a thermodynamic analysis of the gas phase at dissociative evaporation of SiC in the temperature interval (1500-3150 K) is carried out.
Abstract: The thermodynamic analysis of the gas phase at the dissociative evaporation of SiC in the temperature interval (1500–3150) K is carried out. On the basis of the obtained results of the thermodynamic analysis the composition of the equilibrium gas phase above silicon carbide and the “extents of development” of reactions of silicon carbide dissociation and evaporation are determined. The thermodynamic analysis shows that the composition and the stoichiometry of the gas phase above silicon carbide strongly depend on the temperature, and this dependence it is necessary to be taken into account in the analysis of the growth processes of silicon carbide monocrystals and epitaxial layers. [Russian Text Ignored].

Journal ArticleDOI
C. Rein1, D. Demus
TL;DR: In this paper, a modified Simon-Glatzel-equation T = T 0(1 + p/b)a exp (cp) allows to calculate the transition temperatures T also in cases of strongly non-linear relations.
Abstract: In order to describe mathematically the pressure dependence of phase transition temperatures we have derived an equation using the following assumption: i. The transition enthalpy ΔtH = const. ii. The transition volume ΔtV depends on the pressure p according to: The modified Simon-Glatzel-equation T = T0(1 + p/b)a exp (cp) allows to calculate the transition temperatures T also in cases of strongly non-linear relations. Eine Gleichung zur Beschreibung der Druckabhangigkeit von Phasenumwandlungstemperaturen wurde auf der Basis folgender Annahmen abgeleitet: i. Die Phasenumwandlungsenthalpie ΔtH = const. ii. Das Phasenumwandlungsvolumen ΔtV hangt entsprechend der Beziehung vom Druck ab. Die modifizierte Simon-Glatzel-Gleichung T = T0(1 + p/b)a exp (cp) gestattet die Berechnung der Phasenumwandlungstemperaturen auch bei ausgepragtem nichtlinearen Verlauf einer Phasenumwandlungskurve.

Journal ArticleDOI
TL;DR: Both p-type and n-type CuInSe2 single crystals were implanted with 40 keV 130Xe+ ions up to doses of 5 · 1016 cm−2.
Abstract: Both p-type and n-type CuInSe2 single crystals were implanted with 40 keV 130Xe+ ions up to doses of 5 · 1016 cm−2. Implanted layers on p-type substrates showed an initial increase of the resistivity followed by a continuous decrease of the resistivity at higher doses. Implanted layers on n-type substrates gave also an increase of the resistivity at lower doses, but at higher doses a conductivity type conversion from n-type to p-type took place, followed by a decrease of the resistivity. To explain the experimental results it is supposed that the increase of the resistivity is mainly due to charge carrier scattering at extended defects while the decrease of the resistivity at high doses is due to the predominant creation of intrinsic acceptor states during implantation. Sowohl p- als auch n-leitende CuInSe2-Einkristalle wurden mit 40 keV 130Xe+-Ionen bis zu einer Dosis von 5 · 1016 cm−2 implantiert. Implantierte Schichten auf p-leitenden Substraten zeigten zunachst einen Anstieg des spezifischen Widerstands, dem bei hoheren Dosen ein stetiger Abfall des spezifischen Widerstands folgte. Implantierte Schichten auf n-leitenden Substraten ergaben bei niedrigen Dosen gleichfalls einen Anstieg des spezifischen Widerstands. Bei hoheren Dosen fand jedoch ein Umschlag des Leitungstyps von n-Leitung zu p-Leitung statt, gefolgt von einem Abfall des spezifischen Widerstands mit weiter steigender Dosis. Zur Erklarung der experimentellen Ergebnisse wird angenommen, das der Anstieg des spezifischen Widerstands im wesentlichen durch Ladungstragerstreuung an ausgedehnten Defekten verursacht wird, wahrend der Widerstandsabfall bei hohen Dosen durch die vorherrschende Erzeugung von Eigendefektakzeptoren bei der Implantation bedingt ist.

Journal ArticleDOI
TL;DR: In this paper, a simple empirical relationship has been established for the estimation of lattice energies for alkali halide crystals directly from the values of interionic distances, and a new relation has also been proposed between the lattice energy and plasma energy.
Abstract: A simple empirical relationship has been established for the estimation of lattice energies for alkali halide crystals directly from the values of interionic distances. Another new relation has also been proposed between the lattice energy and plasma energy. The calculated plasma energy values are utilized in the estimation of electronic polarizability in alkali halide crystals, in order to lest the applicability of the proposed relations. Good agreement is observed between the computed and literature values of electronic polarizability. The merits of the present approach is discussed

Journal ArticleDOI
TL;DR: The crystal and molecular structures of 1,18-dibromooctadecane were determined precisely by X-ray diffraction method as discussed by the authors, and the results obtained are as follows: empirical formula, C18H36Br2, formula weight Mr = 412.6(3) A3, valeur Z, Z = 2, densite, calculee, Dx = 1.364 g/cm3, longueur d'onde des rayons X.
Abstract: The crystal and molecular structures of 1,18-dibromooctadecane are determined precisely by X-ray diffraction method. The results obtained are as follows: empirical formula, C18H36Br2, formula weight Mr = 412.27, crystal system, monoclinic, space group, P21/n, lattice parameters, a = 5.496(1), b = 5.403(1), c = 34.374(4) A, β = 94.50(1)°, volume of unit cell, V = 1017.6(3) A3, Z value, Z = 2, calculated density, Dx = 1.346 g/cm3, wave length of X-ray, λ(CuKα) = 1.5418 A, absorption coefficient, μ(CuKα) = 49.64 cm−1, F(000) = 428.00, temperature, T = 293 ± 1 K, R factor, R = 0.052, weighted R factor, Rw = 0.078 for 1019 unique observed reflection [I > 3σ (I)]. There are no unusual bond distances or angles. The structure obtained here is quite similar to that of 1,12-dibromododecane. Les structure cristalline et moleculaire du 1,18-dibromoctadecane sont determinees precisement par diffraction des rayons X. Les resultats obtenus sont comme suit: formule empirique, C18H36Br2, poids formule Mr = 412.27, systeme cristalline, monoclinique, groupe spatial, P21/n, parametre grillage a = 5.496(1), b = 5.403(1), c = 34.374(4) A, β = 94.50(1)°, volume de cellule unitee, V = 1017.6(3) A3, valeur Z, Z = 2, densite, calculee, Dx = 1.364 g/cm3, longueur d'onde des rayons X. λ(CuKα) = 1.5418 A, coefficient d'absorption, μ(CuKα) = 49.64 cm−1, F(000) = 428.00, temperature, T = 293 ± 1K, facteur R, R = 0.052, facteur R pesee, Rw = 0.078, pour 1019 unique reflects observes. Il n'y a pas de anormalite de distance ou anlge de liaison. Cette structure obtenue ici est un tout a fait semblable a celle du 1,12-dibromododecane.

Journal ArticleDOI
TL;DR: The crystal structure of angenomalin (8,9-dihydro-8-(1-methylethenyl)-2 H-furo[2,3-h]-1-benzopyran-2-one) was determined by X-ray structure analysis.
Abstract: The crystal structure of angenomalin (8,9-dihydro-8-(1-methylethenyl)-2 H-furo[2,3-h]-1-benzopyran-2-one) was determined by X-ray structure analysis. It crystallizes in the orthorhombic space group P212121 with cell parameters a = 5.210(1), b = 10.407(1), c = 20.478(2) A. The structure was solved by direct methods and refined to R = 0.037. The coumarin moiety is planar and the crystal structure is stabilized by van der Waals interactions.

Journal ArticleDOI
TL;DR: Optical absorption spectra of n-type CuInSe2 single crystals were evaluated by means of photoacoustic spectroscopy in the photon energy range from 0.94 to 1.02 eV as discussed by the authors.
Abstract: Optical absorption spectra of n-type CuInSe2 single crystals were evaluated by means of photoacoustic spectroscopy in the photon energy range from 0.94 to 1.02 eV. At photon energies below 0.99 eV the spectra exhibit exponential tails that are ascribed to the presence of shallow impurity states. At higher photon energies the absorption coefficients follow the relation for direct allowed optical transitions between parabolic bands. The parameters of this relation are determined and compared with previous measurements. Optische Absorptionsspecktren n-leitender CuInSe2-Einkristalle wurden mit Hilfe der photoakustischen Spektroskopie im Photonenenergiebereich von 0.94 bis 1.02 eV bestimmt. Bei Photonenergien unterhalb 0.99 eV zeigen die Absorptionsspektren exponentielle Auslaufer, die dem Vorhandensein flacher Storzellen zugeschrieben werden. Bei hoheren Photonenenergien folgen die Absorptions-koeffizienten der Beziehung fur direkte erlaubte optische Ubergange zwischen parabolischen Bandern. Die Parameter dieser Beziehung werden bestimmt und mit fruheren Messungen verglichen.

Journal ArticleDOI
TL;DR: In this article, the influence of temperature on the electrical conductivity, Hall effect, Hall mobility and the carrier concentration was investigated in the temperature range 200-400 K. The scattering mechanism of the charge carrier was discussed in the same temperature range.
Abstract: Electronic transport measurements were made on single crystal samples of Tl 2 Se 3 . The crystals were prepared by a special design based on Bridgman technique. The influence of temperature on the electrical conductivity, Hall effect, Hall mobility and the carrier concentration was investigated in the temperature range 200-400 K. The energy gap as well as the ionization energy were calculated. The scattering mechanism of the charge carrier was discussed in the same temperature range

Journal ArticleDOI
TL;DR: Tin monoselinide thin films were obtained by solid state reaction in vacuum and characterised by X-ray diffraction and subjected to resistivity and optical absorbance measurements as discussed by the authors.
Abstract: Tin monoselinide thin films were obtained by solid state reaction in vacuum. They were characterised by X-ray diffraction and subjected to resistivity and optical absorbance measurements. The data were analysed for obtaining activation energy and band gap. The effects of varying deposition parameters were studied. These films are concluded to be superior to those obtained directly from the compound semiconductor.

Journal ArticleDOI
TL;DR: Li et al. as mentioned in this paper proposed an approach to solve the problem by using the knowledge from China's southwest inst tech phys,chengdu,peoples r china;li, hp (reprint author), sichuan univ,dept mat science,cheungdu 610064,
Abstract: acad sinica,int ctr mat phys,shenyang,peoples r china. southwest inst tech phys,chengdu,peoples r china.;li, hp (reprint author), sichuan univ,dept mat sci,chengdu 610064,peoples r china

Journal ArticleDOI
Xu Jun1, Ma Xiaoshan1, Zhang Xinmin1, Shen Yafang1, Wu Guangzhao1 
TL;DR: In this article, the orientation of all developing facets on the magnetoplumbite crystal LMA is determined by means of X-ray and optical methods, and the Miller indices are calculated.
Abstract: The magnetoplumbite crystal LMA is grown by the CZ technique. The orientations of all developing facets on the crystals are determined by means of X-ray and optical methods, and Miller indices are calculated. According to the PBC theory, the relations between the morphology of LMA crystal and its structure are explained.

Journal ArticleDOI
TL;DR: In this paper, the luminescence spectra of tetragonal and monoclinic ZrO2 · 0.01 Eu and of Zr O2 · n H2O:0.1 Eu were obtained by excitation at 254 nm and at 365 nm.
Abstract: Luminescent materials with composition ZrO2:0.01 Eu were prepared by co-precipitation of zirconium and europium hydroxides and subsequent thermal decomposition at relatively low temperature. A stabilization of tetragonal ZrO2 prepared on this way is found. The structure of the prepared samples was investigated. The luminescence spectra of tetragonal and of monoclinic ZrO2 · 0.01 Eu and of ZrO2 · n H2O:0.01 Eu by excitation at 254 nm and at 365 nm are presented. Luminophore der Zusammensetzung ZrO2:0.01 Eu sind bei der gleichzeitigen Fallung von Zirconium- und Europiumhydroxiden bei nachfolgender Temperaturbehandlung bei relativ niedrigen Temperaturen hergestellt worden. Die Phasenzusammensetzung der Proben wurde untersucht. Eine Stabilisierung des tetragonalen ZrO2 bei Temperaturbehandlung von ZrO2 · n H2O wird diskutiert. Die Lumineszenzspektren von tetragonalem und monoklinem ZrO2:0.01 Eu und ZrO2 · n H2O:0.01 Eu werden vorgelegt.

Journal ArticleDOI
TL;DR: In this paper, the optical phonons at k = 0 of TlSbS2, TlsbSe2, and Tl3sbS3 have been investigated by infrared reflectivity measurements from 50 to 4000 cm−1 at 300 K. The dielectric constant dispersion for E ǫ a and E b has been determined by classical dispersion relations.
Abstract: The optical phonons at k = 0 of TlSbS2, TlSbSe2, and Tl3SbS3 have been investigated by infrared reflectivity measurements from 50 to 4000 cm−1 at 300 K. The factor group analysis of vibrational modes of TlSbS2 and Tl3SbS3 crystal lattices has been made. The dielectric constant dispersion for E ‖ a and E ‖ b has been determined by classical dispersion relations. The Szigeti effective charges, the Born dynamic effective charge, and the Tl, Sb, S (Se) relative ion charges were calculated in dependence on the polarization of the incident light. [Russian Text Ignored].