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1
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Thermal Wave Measurements with a Mirage Detection for Investigation of Thermal Diffusivity of GdCa_4O(BO_3)_3 Single Crystals

100%
Bodzenta J., Kaźmierczak-Bałata A., Łukasiewicz T., Hofman B., Kucytowski J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6A
A-27-A-32
EN
Single crystals of GdCa_4O(BO_3)_3 were examined to determine their thermal properties. Samples were grown by the Czochralski pulling technique. There were three types of samples: a pure crystal, the crystal doped with neodymium (4 at.% of Nd), and the third one doped with ytterbium (7 at.% of Yb). All samples were rectangular prisms with edges parallel to the axes of the optical indicatrix X, Y, Z (principal axes). The thermal diffusivity was determined by means of the thermal wave method with the optical detection of the temperature disturbance based on a mirage effect. Experimental results showed anisotropy of the thermal diffusivity. The thermal diffusivity along Y direction has the highest value while values obtained in X and Z axes are much lower. Dopants cause decrease in the thermal diffusivity for all investigated directions.
2
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Spectroscopic and Laser Properties of Different Materials Doped with Pr^{3+} Ions

86%
Mierczyk Z., Kaczmarek S., Kopczyński K., Frukacz Z., Pracka I., Łukasiewicz T.
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EN
Examined praseodymium doped crystals with 1 at.% of Pr^{3+} ions for Y_{3}Al_{5}O_{12} (YAG), SrLaGa_{3}O_{7} (SLGO) hosts and 3 at.% of Pr^{3+} ions for YAlO_{3} (YAP) hosts were produced using Czochralski method. The luminescence for the range of 200÷800 nm and absorption spectra for a wide range of 200÷6000 nm, for Pr^{3+}:YAG, Pr^{3+}:SLGO and Pr^{3+}:YAP crystals have been measured. A free-running laser emission of λ=0.744 μm for Pr:YAG and λ=0.729 μm for Pr:SLGO for two different transmissions of output mirrors has been obtained.
3
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X-Ray Topographic Studies of Defect Structure in YVO_4 Crystals

86%
Wieteska K., Wierzchowski W., Łukasiewicz T., Wierzbicka E., Malinowska A., Lefeld-Sosnowska M., Graeff W.
Acta Physica Polonica A
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2008
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vol. 114
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issue 2
455-461
EN
The perfection of YVO_4 crystals, which are predicted to replace formerly used YAG garnets due to higher quantum efficiency and lower excitation level, was studied. The investigations of Czochralski grown undoped YVO_4 single crystals were performed mainly by means of X-ray topographic methods. Both synchrotron and conventional X-ray sources were used. The study revealed relatively high density of weak point-like contrasts which can be most probably interpreted as dislocation outcrops. In regions of the crystal close to its boundary we observed glide bands. It was also found that in some regions the dislocations form local subgrain boundaries. The white beam back reflection and monochromatic beam topography allowed to evaluate a local misorientation which not exceeded several angular minutes. No segregation fringes were observed proving a good homogeneity of chemical composition.
4
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Spectroscopic and Laser Properties of LiNbO_{3}:Dy^{3+} Crystals

73%
Malinowski M., Myziak P., Piramidowicz R., Pracka I., Łukasiewicz T., Surma B., Kaczmarek S., Kopczyński K., Mierczyk Z.
Acta Physica Polonica A
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1996
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vol. 90
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issue 1
181-189
EN
The spectroscopic properties of trivalent dysprosium (Dy^{3+}) doped LiNbO_{3} crystals have been investigated at various temperatures. Absorption, emission, excitation and lifetime measurements have been performed and discussed in the framework of Judd-Ofelt approach. The stimulated emission cross sections of the strongest transitions of Dy ^{3+} ion have been estimated. A stimulated emission has been demonstrated in the near infrared.
5
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Defect Structure Formed at Different Stages οf Growth Process in Erbium, Calcium and Holmium Doped YVO_{4} Crystals

73%
Malinowska A., Wierzbicka E., Lefeld-Sosnowska M., Wieteska K., Wierzchowski W., Łukasiewicz T., Świrkowicz M., Graeff W.
Acta Physica Polonica A
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2010
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vol. 117
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issue 2
328-331
EN
The defect structure of YVO_{4} single crystals doped with Er^{3+}, Ho^{3+} and Ca^{2+} were studied by X-ray diffraction topographic methods, using laboratory and synchrotron radiation sources. Variously developed block structure was the dominating imperfection of the investigated crystals observed both in conventional Lang and synchrotron topographs. The evaluation of block misorientation was realised by means of superimposed projection and section white beam synchrotron radiation topographs. More possibilities of following the mutual rotation of blocks were provided by means of white beam synchrotron radiation WBSR projection topographs exposed through the fine mesh.
6
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X-ray Topographic Investigations of Domain Structure in Czochralski Grown Pr_{x}La_{1-x}AlO_{3} Crystals

73%
Wieteska K., Wierzchowski W., Malinowska A., Turczyński S., Lefeld-Sosnowska M., Pawlak D., Łukasiewicz T., Graeff W.
Acta Physica Polonica A
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2010
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vol. 117
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issue 2
268-271
EN
In the present paper X-ray diffraction topographic techniques were applied to a number of samples cut from Czochralski grown Pr_{x}La_{1-x}AlO_{3} crystals with different ratio of praseodymium and lanthanum. Conventional and synchrotron X-ray topographic investigations revealed differently developed domain structures dependent on the composition of mixed praseodymium lanthanum aluminium perovskites. Some large mosaic blocks were observed together with the domains. In the best crystals, X-ray topographs revealed striation fringes and individual dislocations inside large domains. Synchrotron topographs allowed us to indicate that the domains correspond to three different crystallographic planes, and to evaluate the lattice misorientation between domains in the range of 20-50 arc min.
7
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Synchrotron Diffraction topography in Studying of the Defect Structure in Crystals Grown by the Czochralski Method

73%
Wierzchowski W., Wieteska K., Malinowska A., Wierzbicka E., Lefeld-Sosnowska M., Świrkowicz M., Łukasiewicz T., Pajączkowska A., Paulmann C.
Acta Physica Polonica A
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2013
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vol. 124
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issue 2
350-359
EN
The synchrotron diffraction topography had been widely used for investigation of the structural defects in crystals grown by the Czochralski method. Similarly as conventional diffraction topography, the synchrotron topography consists in recording with high spatial resolution of the beam formed by the Bragg reflection from the crystal. The advantages of synchrotron sources come from the possibilities of using the wavelength from a wide spectral range, improved high spatial resolution and collimation of the beam as well as from shortening the time necessary for the investigation. The synchrotron diffraction topography includes experimentally simpler white beam topography and more complicated monochromatic beam (multicrystal) topography, where the beam is formed by monochromators. In the case of Czochralski-grown crystals the synchrotron diffraction topography can be used for studying of the individual dislocations and their complexes such as glide bands or sub-grain boundaries, individual blocks, twinning, the domain structure and various segregation effects negatively affecting crystal properties. In addition, the topographical investigation can provide information concerning the reasons for the generation of defects, useful in the improving of the technology. In the present paper the possibilities of the synchrotron diffraction topography are discussed on the basis of several investigations of the Czochralski-grown oxide and semiconductor crystals, performed by the authors at HASYLAB. The majority of the results concern the oxide crystals grown at the Institute of Electronic Materials Technology, in particular garnets, orthovanadates, mixed calcium barium and strontium niobates as well as praseodymium lanthanum aluminates.
8
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Characterisation of the Defect Structure in Gadolinum Orthovanadate Single Crystals Grown by the Czochralski Method

73%
Wierzbicka E., Malinowska A., Wieteska K., Wierzchowski W., Lefeld-Sosnowska M., Świrkowicz M., Łukasiewicz T., Paulmann C.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
906-909
EN
The GdVO_4 single crystals, both undoped and doped with erbium or thulium, were studied by means of X-ray diffraction topographic methods exploring laboratory and synchrotron radiation sources. Variously developed block structure, caused probably by thermal stresses, was revealed. The highest crystallographic perfection was observed in the crystal doped with 4 at.% of thulium, which was free of the grain boundaries in the end part. Contrary to that, the differences in structural perfection between samples cut out from various regions of the crystal and for different kinds of doping, were less distinct in other crystals. The diffraction topographic methods enabled the statement that the misorientation between various blocks is in the range of several arc minutes.
9
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Synchrotron Topographic Studies of Domain Structure in Czochralski Grown Pr_xLa_{1-x}AlO_3 and Pr_xLa_{1-x-y}Mg_yAlO_3 Crystals

73%
Wieteska K., Wierzchowski W., Malinowska A., Turczyński S., Lefeld-Sosnowska M., Pawlak D., Łukasiewicz T., Paulmann C.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
910-914
EN
A domain structure and crystallographic defects in Czochralski grown single crystals of Pr_xLa_{1-x}AlO_3 and Pr_xLa_{1-x-y}Mg_yAlO_3 were characterised with a number of methods including conventional and synchrotron X-ray diffraction topography, and polariscopic micrography. The observed twin domain systems were located perpendicularly to 〈100〉_{pcub} and 〈110〉_{pcub} (pseudocubic) directions. It has been confirmed that the domains are of the same orientation and a twin character as those described in literature for LaAlO_3 and LaGaO_3 crystals. The use of section transmission topography enabled to indicate that the domains are perpendicular to the (100)_{pcub} surface of the samples. The misorientation of lattice in the domains was evaluated from the white beam topographs and a tendency of its increase with increasing concentration of praseodymium was revealed.
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