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1

Raman Spectroscopy of LiFePO_4 and Li_3V_2(PO_4)_3 Prepared as Cathode Materials

100%

Ziółkowska D., Korona K., Kamińska M., Grzanka E., Andrzejczuk M., Wu S., Chen M.

Acta Physica Polonica A

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2011

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vol. 120

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issue 5

973-975

EN

Structure of samples of lithium iron vanadium phosphates of different compositions were investigated by X-rays, electron microscopy and Raman spectroscopy. The investigated salts were mainly of olivine-like and NASICON-like structures. The X-ray diffraction and the Raman scattering show different crystalline structures, which is probably caused by difference between cores of the crystallites (probed by X-rays) and their shells (probed by the Raman scattering). Most of the Raman spectra were identified with previously published data, however in the samples with high vanadium concentration we have observed new, not reported earlier modes at 835 cm^{-1} and 877 cm^{-1}, that we identified as oscillations related to V_2O_7^{4-} or VO_4^{3-} anions.

2

Diffraction Studies of Nanocrystals: Theory and Experiment

84%

Palosz B., Grzanka E., Gierlotka S., Stel'makh S., Pielaszek R., Bismayer U., Neuefeind J., Weber H., Palosz W.

Acta Physica Polonica A

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2002

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vol. 102

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issue 1

57-82

EN

Based on theoretical calculations of powder diffraction data it is shown that the assumption of the infinite crystal lattice for small particles is not justified, leads to significant changes of the diffraction patterns, and may lead to erroneous interpretation of the experimental results. An alternate evaluation of diffraction data of nanoparticles, based on the so-called "apparent lattice parameter", alp, is proposed.

3

Generation and Relaxation of Microstrains in GaN Nanocrystals under Extreme Pressures

84%

Grzanka E., Palosz B., Gierlotka S., Pielaszek R., Bismayer U., Janik J., Wells J., Palosz F., Porsch F.

Acta Physica Polonica A

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2002

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vol. 102

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issue 2

167-174

EN

Nanocrystalline powders of GaN with grain sizes ranging from 2 to 30 nm were examined under high external pressures by in situ diffraction techniques in a diamond anvil cell at DESY (HASYLAB, Station F3). The experiments on densification of pure powders under high pressure were performed without a pressure medium. The mechanism of generation and relaxation of internal strains and their distribution in nanoparticles was deduced from the Bragg reflections recorded in situ under high pressures at room temperature. The microstrain was calculated from the full-width at half-maximum (FWHM) values of the Bragg lines. It was found that microstrains in GaN crystallites are generated and subsequently relaxed by two mechanisms: generation of stacking faults and change of the size and shape of the grains occurring under external stress.

4

Fabrication and Physical Properties of SiC-GaAs Nano-Composites

84%

Kalisz G., Grzanka E., Wasik D., Świderska-Środa A., Gierlotka S., Borysiuk J., Kamińska M., Twardowski A., Pałosz B.

Acta Physica Polonica A

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2005

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vol. 108

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issue 4

717-721

EN

Nano-composites consisting of primary phase of hard nanocrystalline SiC matrix and the secondary nanocrystalline semiconductor (GaAs) phase were obtained by high-pressure zone infiltration. The synthesis process occurs in three stages: (i) at room temperature the nanopowder of SiC is compacted along with GaAs under high pressure up to 8 GPa, (ii) the temperature is increased above the melting point of GaAs up to 1600~K and, the pores are being filled with liquid, (iii) upon cooling GaAs nanocrystallites grow in the pores. Synthesis of nano-composites was performed using a toroid-type high-pressure apparatus (IHPP of the Polish Academy of Sciences, Warsaw) and six-anvil cubic press (MAX-80 at HASYLAB, Hamburg). X-ray diffraction studies were performed using a laboratory D5000 Siemens diffractometer. Phase composition, grain size, and macrostrains present in the synthesized materials were examined. Microstructure of the composites was characterized using scanning electron microscopy and high resolution transmission electron microscopy. Far-infrared reflectivity measurements were used to determine built-in strain.

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4 Acta Physica Polonica A

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1 Wu S.

1 Ziółkowska D.

1 Świderska-Środa A.

Raman Spectroscopy of LiFePO_4 and Li_3V_2(PO_4)_3 Prepared as Cathode Materials

Diffraction Studies of Nanocrystals: Theory and Experiment

Generation and Relaxation of Microstrains in GaN Nanocrystals under Extreme Pressures

Fabrication and Physical Properties of SiC-GaAs Nano-Composites