Papers by Wojciech Paszkowicz
Powder Diffraction, Mar 1, 2001
LiCu2O2 crystals grown by spontaneous crystallization from the fluxed melt were studied by powder... more LiCu2O2 crystals grown by spontaneous crystallization from the fluxed melt were studied by powder X-ray diffraction. The phase analysis shows that the applied growth conditions are suitable for preparation of a single-phase compound. The as-grown crystals contain only traces of foreign phases (Li2CuO2, CuO, Cu2O) typical for preparation of the LiCu2O2 compound. Attempts to anneal or quench the as-grown crystals led to two-phase samples containing LiCu2O2 and LiCu3O3. X-ray powder diffraction pattern of a LiCu2O2 crystal is reported and compared with literature data. The crystal structure is orthorhombic, space group Pnma, in agreement with literature data. Lattice parameters of the studied sample are a=5.7286(2) Å, b=2.8588(1) Å, and c=12.4143(3) Å. Time evolution of a diffraction pattern illustrates a slow increase of the secondary-phases contribution assumed to be due to interaction of the powdered crystal with humid air. A brief summary of compounds known in the Li–Cu–O system is included
Powder Diffraction, Jun 1, 2003
Results of Rietveld refinement for indium nitride data collected in the temperature range 105-295... more Results of Rietveld refinement for indium nitride data collected in the temperature range 105-295 K are presented. Acicular microcrystals of indium nitride prepared by reaction of liquid indium with nitrogen plasma were studied by X-ray diffraction. The diffraction measurements were carried out at the Swiss-Norwegian Beamline SNBL ͑ESRF͒ using a MAR345 image-plate detector. Excellent counting statistics allowed for refinement of the lattice parameters of InN as well as those of the metallic indium secondary phase. In the studied temperature range, the InN lattice parameters show a smooth increase that can be approximated by a linear function. Lattice-parameter dependencies confirm the trends indicated earlier by data measured using a conventional equipment. The relative change of both the a and c lattice parameters with increasing the temperature in the studied range is about 0.05%. The axial ratio slightly decreases with rising temperature. The experimental value of the free structural parameter, uϭ0.3769͑14͒, is reported for InN for the first time. Its temperature variation is found to be considerably smaller than the experimental error. The thermal-expansion coefficients ͑TECs͒, derived from the linearly approximated lattice-parameter dependencies, are ␣ a ϭ3.09(14)ϫ10 Ϫ6 K Ϫ1 and ␣ c ϭ2.79(16)ϫ10 Ϫ6 K Ϫ1 . The evaluated TECs are generally consistent with the earlier data. For the present dataset, the accuracy is apparently higher for both, the lattice parameters and thermal-expansion coefficients, than for the earlier results. The refined lattice parameter c In of the indium secondary phase exhibits the known strongly nonlinear behavior; a shift ͑⌬T equal about Ϫ50 K͒ of the maximum in c In ͑T͒ dependence is observed with respect to the literature data.
Powder Diffraction, Dec 1, 1999
X-ray powder diffraction pattern for InN synthesized using a microwave plasma source of nitrogen ... more X-ray powder diffraction pattern for InN synthesized using a microwave plasma source of nitrogen is reported. The data were obtained with the help of an automated Bragg-Brentano diffractometer using Ni-filtered CuKa radiation. The lattice parameters for the wurtzite-type unit cell are a o = 3.5378(1) A, c o = 5.7033(1) A. The calculated density is 6.921 ±0.002 g/cm 3 .
Acta Crystallographica Section A, Aug 25, 2013
Acta Crystallographica Section A, Aug 23, 2008
Poster Sessions atom positions based on the response ratio show that there are 1.1 % excited-stat... more Poster Sessions atom positions based on the response ratio show that there are 1.1 % excited-state species in the crystal in which the I-I distance (3.82(2) Å) is contracted from the ground states (4.41(1)Å). While in the case of the discrete dimer complex [Cu2I2(PPh3)(pyz)2], two iodine atoms tend to move out of the {Cu2I2} plane with opposite direction each other. This indicates that the {Cu2I2} rotates around an axis containing two Cu atoms. This variety of the motions of {Cu2I2} frameworks will be concerned with the geometry of the frame at the ground state and solid-state luminescent properties.
Powder Diffraction, Jun 1, 2000
Powder X-ray diffraction data are reported for semimagnetic semiconductor Hg 089 Fe 011 S and Hg ... more Powder X-ray diffraction data are reported for semimagnetic semiconductor Hg 089 Fe 011 S and Hg 0 98 Co 0 02 S crystals grown by the Bridgman method and for Hg 0 80 Mn 0 2 oS crystal synthesized by a solid-state reaction method. The crystals have the sphalerite structure of metacinnabar (sphalerite-type high-temperature polymorph of HgS, space group F43m). Phase analysis does not show any trace of other phases. The lattice parameters of the studied samples are a = 5.803 20(5) A, 5.8063(1) A and 5.839 80(6) A, respectively. The calculated density is reported.
Powder Diffraction, Mar 1, 1998
The X-ray powder diffraction patterns for three bulk Z ^ _ x MgjSe crystals are reported. The dat... more The X-ray powder diffraction patterns for three bulk Z ^ _ x MgjSe crystals are reported. The data were obtained with the help of an automated Bragg-Brentano diffractometer using Ni-filtered Cu Ka radiation. One of the samples is of the sphalerite structure type, and it has the magnesium content slightly below the sphalerite-wurtzite phase transition. The two remaining ones are of the wurtzite type with low and high magnesium content. The lattice constant for the sphalerite Zn 086 Mg 014 Se is a o = 5.7011(1) A. For the wurtzite alloys the lattice constants are a 0 = 4.0540(1) A, c o = 6.627O(2) A (for Zn 072 Mg 028 Se), a o = 4.1195(l) A, c o =6.6941(2) A (for Zn 037 Mg 063 Se).
Applied Physics A, Dec 29, 2013
Structural and elastic properties of chalcopyritetype CuInSe 2 are determined in almost full stab... more Structural and elastic properties of chalcopyritetype CuInSe 2 are determined in almost full stability range of temperature from 11 to 1,073 K, by in situ X-ray diffraction, employing a synchrotron-radiation source. The studied polycrystalline sample was prepared from a stoichiometric single crystal. Phase analysis reveals the formation of a trace amount of indium oxide impurity phase at the highest temperatures studied. From the obtained smooth latticeparameter dependencies on temperature, the temperature dependencies of thermal expansion coefficients are derived. These coefficients are found to follow the trends previously reported for narrow temperature intervals. The present results provide a clear experimental evidence that the linear expansion coefficient is slightly negative below 47 K in both, a and c, directions; this temperature limit is in between the previously reported theoretical value (35 K) and the experimental ones (60 and 80 K) of such limit.
Acta Crystallographica Section A, Aug 22, 2011
Thin films built from binary IIIV nitrides or from their solid solutions are basic components of ... more Thin films built from binary IIIV nitrides or from their solid solutions are basic components of modern optoelectronic devices. In particular, indium nitride is a component suitable for high-speed electronics and solar cells. Experimental data on the bulk nitride material behaviour under specific thermal conditions (e.g., on variation of its stability, resistance to oxidation, thermal expansion coefficient with temperature) provide a valuable basic information needed for design and development of such devices. The properties such as decomposition temperature, oxidation rate at elevated temperatures, and thermal expansion are of importance for technologies of growth of low-dimensional structures. The current knowledge of thermal properties [1-3] may require an extension through studies in neutral or oxidizing environment in broad temperature ranges. The aim of the present work is to present selected experimentally determined temperature-dependent properties (thermal decomposition, interaction with air, thermal expansion) and discuss them on the basis of existing literature data. Polycrystalline indium nitride samples differing by grain size were sealed in capillaries filled with air and in argon, and then studied by Xray diffraction in a broad temperature range. High-resolution powder diffractometer at the B2 beamline (DORIS-III, Hasylab, DESY) equipped in a position-sensitive detector ensured collection of data with excellent counting statistics. The X-ray diffraction experiments were conducted at increasing temperatures using a step of 50 K or less; the experiments were stopped when the full decomposition of InN was concluded. High-resolution electron microscopy was used for determination of the microstructure and crystallite size. The structures of InN and minority phases as well as those of the oxidation products were refined using the Rietveld method. The obtained results demonstrate that the decomposition is, as expected, much faster for the sample composed of small grains. The oxide formation, observed when heating indium nitride in air, is attributed to oxidation of the nitride (at moderate temperatures) or to interaction of oxygen with indium vapour (at high temperatures). Thermal expansion was determined from the lattice parameters variation between 22 and 900 K. In this range, the unit-cell volume increases from 61.78 to 62.5 Å 3 , whereas the thermal expansion coefficient, α V , increases from 0 to 19×10-6 K-1. Acknowledgements: The partial support of the European Community in the framework of ITN RAINBOW
Thin films of GdMnO 3 were deposited by RF magnetron sputtering on SrTiO 3 (100) and Si (100) sub... more Thin films of GdMnO 3 were deposited by RF magnetron sputtering on SrTiO 3 (100) and Si (100) substrates. XRD analysis revealed that GdMnO 3 films grown on SrTiO 3 (100) substrates are well textured. The out-of-plane c axis is elongated by 0.75 % - 1.10 % in comparison to bulk lattice value and depends on film thickness. The minimal elongation was found for the GdMnO 3 film deposited on a La 0.7 Sr 0.3 MnO 3 (LSMO) buffer layer. M/H vs. T (5<T<100K) as well as M vs. H (T=5K) dependences obtained for a 100 nm thick sample of GdMnO 3 / SrTiO 3 (100) point to the absence of magnetic anisotropy unlike the case of a GdMnO 3 single crystal. This effect is attributed to the significant structural disorder due to misfit stress. AC resistivity measurements show a measurable influence of the static magnetic field on the impedance parameters, in accordance with the (H, T)-phase diagram of the GdMnO 3 single crystal.
Computer methods in materials science, 2013
Crystals
The structural and luminescence properties of a new material, Ca10.5−xNix(VO4)7, formed by substi... more The structural and luminescence properties of a new material, Ca10.5−xNix(VO4)7, formed by substitution of a fraction of calcium by nickel, are studied as a function of the Ni content (x). The powder X-ray diffraction results for the polycrystals, synthesized using a solid-state reaction method, show that in the studied temperature range (300–1150 K), the structure of the unsubstituted material (space group R3c, whitlockite-β-Ca3(PO4)2 structure type) is conserved up to the solubility limit, x = 0.72(2), determined on the basis of variation of unit cell size with x. The samples of nominal composition exceeding this limit contain a significant amount of the impurity phase.The structural refinements demonstrate that Ni atoms preferentially occupy the M5 site (one of the five independent Ca sites, M1–M5). The unit cell size was equally studied in the range of 300–1150 K, leading to the determination of the thermal expansion coefficients. It was found that with rising Ni content, the ro...
Aluminium nitride (AlN) nanopowder was successfully synthesized from aluminium oxide via a single... more Aluminium nitride (AlN) nanopowder was successfully synthesized from aluminium oxide via a single-step reaction with ammonia as a source of nitrogen. The process was carried out in a horizontal mullite tube reactor located in an electric furnace in the ranges of temperature, time and gas ? ow rate of 1050-1350 oC, 1-5 h and 100-150 l/h, respectively. Nanopowders of �� -Al2O3 and �. -Al2O3 were used as starting materials. In? uence of temperature, time, gas ? ow rate and type of aluminium oxide on reaction productivity, powder morphology and product phase composition was investigated. Dynamic light scattering (DLS), Ramman spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and specio c surface area measurements by the BET isotherm technique were used to characterized the obtained materials. Aluminium nitride prepared under optimal reaction conditions, comprising the reaction time of 5 h, the temperature of 1250 oC, and the gas? ow rate of 150 l/h, was found to be nanocrystalline powder with a mean crystallite size of about 60 nm in the synthesis from gamma aluminium oxide and 65 nm in case of alfa aluminium oxide as a starting material. The productivity of nitridation reaction in such conditions was close to 99%, basing on gravimetric measurements. In case of the synthesis from gamma oxide, PXRD analysis indicated the pure hexagonal aluminium nitride structure which was cono rmed by TEM analysis. In case of alfa aluminium oxide nitridation, the obtained aluminium nitride contained the unreacted oxide. Additionally, the investigation of average agglomerate sizes in the water suspension conducted by DLS showed that aluminium nitride obtained from �� -Al2O3 had an average particle size of 282 nm, and in the case of �. -Al2O3 used as a starting material it was 2219 nm..
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Papers by Wojciech Paszkowicz