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Papers by Agnieszka Szysiak

Journal of Alloys and Compounds

The pseudo-binary phase diagram of the YAlO3 (YAP)–NdAlO3 (NAP) system was determined by differen... more The pseudo-binary phase diagram of the YAlO3 (YAP)–NdAlO3 (NAP) system was determined by differential thermal analysis (DTA) and X-ray powder diffraction (XRD) measurements. High purity nanocrystalline powders and small single crystals of Y1−xNdxAlO3 (0≤x≤1) have been produced successfully by modified sol–gel (Pechini) and micro-pulling-down methods, respectively. Both end members show high mutual solubility >25% in the solid phase, with a miscibility gap for intermediate compositions. A solid solution with x≈0.2 melts azeotropic ca. 20° below pure YAP. Such crystals can be grown from the melt without segregation. The narrow solid/liquid region near the azeotrope point could be measured with a “cycling” DTA measurement technique.

Journal of nanoscience and nanotechnology, 2009

Spectroscopic features of Eu3+, Nd3+ and Er3+ in nanocrystalline samples of gallium gadolinium ga... more Spectroscopic features of Eu3+, Nd3+ and Er3+ in nanocrystalline samples of gallium gadolinium garnet prepared by a modified sol-gel method were investigated in order to assess the structural compatibility of the material with a single crystal counterpart. Emission spectra and decay curves of luminescent admixtures were recorded and analysed. Observed distribution of spectral line intensities and single exponential time dependence of luminescence decay curves indicate strongly that the static disorder in the neighbourhood of luminescent ions is not significant, hence structural peculiarities of the garnet lattice encountered in bulk crystals are maintained. It has been concluded that the method of preparation applied is able to furnish good structural quality GGG nanocrystals.

Optical Materials, 2009

The nanocrystalline powders of Y 4 Al 2 O 9 single doped with Nd 3+ , Yb 3+ , Er 3+ and co-doped ... more The nanocrystalline powders of Y 4 Al 2 O 9 single doped with Nd 3+ , Yb 3+ , Er 3+ and co-doped with Nd 3+ and Yb 3+ as well as with Yb 3+ and Er 3+ were obtained by a modified sol-gel method starting from nitrates and acetates rather than citrates. The powders were characterised by X-ray diffraction method, high resolution scanning electron microscopy and luminescence spectroscopy. Close similarity of low temperature emission spectra recorded for Y 4 Al 2 O 9 nanocrystalline powder doped with Nd 3+ and for a single crystal counterpart grown by the micro-pulling technique implies that the sol-gel method applied is able to provide material in which the structural peculiarities encountered in bulk crystals are maintained. Efficiency of nonradiative energy transfer between rare earth ions was assessed based on analysis of luminescence decay curves. It has been concluded that the Y 4 Al 2 O 9 host may be promising for the design of multiple doped phosphors whose emission characteristics are tailored by energy transfer between properly chosen activators.

Materials Research Bulletin, 2009

ABSTRACT Structure, morphology and luminescence properties of nanocrystalline samples of YAl3(BO3... more ABSTRACT Structure, morphology and luminescence properties of nanocrystalline samples of YAl3(BO3)4 (YAB) undoped and doped with neodymium, ytterbium and chromium obtained by the sol–gel method are presented. The best results of synthesis are obtained for mannitol as polymerizing agent. Single phase of nanopowder is obtained for pure YAB. Dopants destroy the compound structure; two other compounds, namely Al18B4O33 and YBO3, were revealed by X-ray investigation. Nanopowders show isometric and needles forms, the calculated size of crystallites is about 60nm. Their optical properties are determined and results are compared to data obtained for single crystal counterparts. It is shown that the influence of rare earth ions incorporated into YBO3 phase on luminescent spectra and excited state relaxation dynamics of the nanopowders is negligibly small when the YBO3 content is of the order of several wt%. Residual impurity phases do not affect significantly spectroscopic properties of YAB nanopowders.

Materials Research Bulletin, 2011

Journal of Alloys and Compounds, 2011

a b s t r a c t YAG:Nd powders obtained by grinding a single crystal and synthesized by modified ... more a b s t r a c t YAG:Nd powders obtained by grinding a single crystal and synthesized by modified sol-gel and combustion methods were embedded at the stage of melting in a multicomponent borate glass to obtain luminescent glass-ceramic systems. Room temperature optical absorption spectra, luminescence spectra at room temperature and at 10 K and micro-Raman spectra were recorded to determine the location of Nd 3+ ions in composite materials. It has been concluded that their luminescence characteristics depend critically on the preparation method hence the morphology of precursor crystalline YAG:Nd powders as a consequence of dissimilar solubility of crystallites in a host glass.

Journal of Alloys and Compounds, 2011

The binary phase diagram of the YAlO 3 (YAP) -NdAlO 3 (NAP) system was determined by differential... more The binary phase diagram of the YAlO 3 (YAP) -NdAlO 3 (NAP) system was determined by differential thermal analysis (DTA) and X-ray powder diffraction (XRD) measurements. High purity nanocrystalline powders and small single crystals of Y 1-x Nd x AlO 3 (0 ≤ x ≤1) have been produced successfully by modified sol-gel (Pechini) and micro-pulling-down methods, respectively. Both end members show high mutual solubility > 25% in the solid phase, with a miscibility gap for intermediate compositions. A solid solution with x ≈ 0.2 melts azeotropic ca. 20 degrees below pure YAP. Such crystals can be grown from the melt without segregation. The narrow solid/liquid region near the azeotrope point could be measured with a "cycling" DTA measurement technique.

Crystal Research and Technology, 2007

Single crystals of GdCa 4 O(BO 3 ) 3 (GdCOB) pure and doped with Eu concentration of 1 and 4 at% ... more Single crystals of GdCa 4 O(BO 3 ) 3 (GdCOB) pure and doped with Eu concentration of 1 and 4 at% were grown by the Czochralski and micropulling-down methods. The distribution of Eu ions in GdCOB crystals was uniform. The substitutions of Eu 3+ in Gd, Ca(1) and Ca(2) cation sites and eventually formation Eu 2+ have been investigated. The spectroscopic properties of crystals are compared with the properties of nanopowders obtained by sol-gel method. Radioluminescence spectra of undoped GdCOB crystal show the characteristic emission of Gd 3+ at about 312 nm, whereas this emission dramatically decreases in Eu-doped crystals upon X-ray excitation, as well as in Eu-doped nanopowders excited in vacuum ultraviolet (VUV) region. The VUV excitation in the range 125-333 nm for Eu-doped samples leads to strong emission in red coming from the 5 D 0 multiplet of Eu 3+ , only. In the photoluminescence decay kinetics of 312 nm emissions substantial shortening and departure for single exponential decay in Eu-doped samples is clearly observed. Higher Eu doping results in further acceleration of the decay. In undoped GdCOB crystal, the lifetime of the Gd 3+ 6 P 7/2 multiplet is 2.79 ms. The Eu 3+ 5 D 0 decay kinetics monitored at 613 nm are rather constant. Numerical fitting of fully exponential curves, reveals lifetimes 2.7 ms for nanopowder and 2.5 ms for single crystal. The results suggest that this material may be used as a red phosphor in plasma display panels in nanopowder form because of strong excitation band of Eu 3+ luminescence in the 160-200 nm regions. Contrary to nanopowder sample, such an excitation band, attributed to the Gd 3+ -O 2charge transfer was not observed in crystal obtained by the micropulling-down method.

Crystal Research and Technology, 2007

Nanopowders of Y 2 O 3 pure, doped and codoped by Nd 3+ , Yb 3+ were obtained by sol-gel method. ... more Nanopowders of Y 2 O 3 pure, doped and codoped by Nd 3+ , Yb 3+ were obtained by sol-gel method. Solution with ethylene glycol was choosed as the proper solution where crystallites of powder with Nd and Yb dopants had the same size. Finally the one-phased compounds of Y 2 O 3 doped 0.5 at% Nd and 1, 2 or 4 at% Yb were obtained. Grain growth and their morphology were investigated in various temperature and time of heating. The changes of crystallite sizes and lattice constants in relation to the heating time and temperature for the composition Y 2 O 3 doped 0.5 at% Nd and 2 at% Yb are presented. Y 2 O 3 containing 0,5 at% of Nd exhibits intense luminescence bands centered at 920 nm, 1100 nm and 1360 nm whereas a single band at about 1020 nm appears in samples co-doped with neodymium and ytterbium. Luminescence spectra recorded did not depend on the sample preparation procedure and size of grains. OH impurity affects critically the relaxation dynamics of luminescent ion in nanopowders.

Crystal Research and Technology, 2009

The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neo... more The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neodymium were investigated. Nanopowders of GGG:Nd were prepared by modified sol-gel method using acetic acid as complexing agent. This way permitted to incorporate large amounts of dopant (up to 10 %) without destroying garnet structure. Small single crystals of Nd:GGG were grown by a µ-pulling down method and spectroscopic features of nanopowders and their single crystal counterparts were compared. It has concluded that the Nd 3+ ions are located preferentially in the same type of sites in crystal lattices of GGG:Nd nanopowders and their single crystal counterparts. In addition, it follows from the perfect agreement of emission wavelengths and line width recorded for nanopowders and single crystal samples that the crystal lattice of GGG in nanopowders is not distorted.

The XRD, XPS, SEM and magnetic characterization of the nano and single crystals SrLaAlO 4 doped w... more The XRD, XPS, SEM and magnetic characterization of the nano and single crystals SrLaAlO 4 doped with Mn were done. The sol-gel method was used to obtain the nanopowder and SEM imaging confirmed the submicron size of grains. The single crystals were grown by the Czochralski method. All compounds exhibit excess of strontium and deficiency of aluminium. The unit cell volumes increase with the amount of strontium. The electronic structures measured by XPS of the undoped yellowish single crystals and those nominally doped with 0.02 Mn (amber) and 0.1 Mn (olive) are very similar with comparable ratios of the main to the additional lines. It differs in the case of the nanocrystals, where the surface decomposition is observed. The magnetic measurements indicate the presence of the Mn 4+ ions and are in good agreement with the spectroscopic data.

Crystal Research and Technology, 2009

ABSTRACT The nanocrystalline powders of Y4Al2O9 (YAM) pure and doped by Nd, Yb and codoped by Nd ... more ABSTRACT The nanocrystalline powders of Y4Al2O9 (YAM) pure and doped by Nd, Yb and codoped by Nd and Yb were obtained via modified sol-gel method. These powders were characterized by X-ray diffraction method, scanning electron microscopy and high resolution scanning electron microscopy, luminescence spectroscopy and differential thermal analysis (DTA). We obtained single phase powders of crystalline structure with average size 70 nm exhibiting interesting luminescent properties. Efficient non-radiative energy transfer between Nd and Yb was found. DTA confirmed the phase transition at about 1400 °C. From these nanocrystalline powders, the crystals YAM:Yb, YAM:Yb,Nd were grown by micro-pulling down technique. They were cracking during cooling owing to the phase transition. Luminescent properties of YAM:Nd,Yb crystals were identical with properties of corresponding nanopowders within experimental incertitude. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Journal of Alloys and Compounds

The pseudo-binary phase diagram of the YAlO3 (YAP)–NdAlO3 (NAP) system was determined by differen... more The pseudo-binary phase diagram of the YAlO3 (YAP)–NdAlO3 (NAP) system was determined by differential thermal analysis (DTA) and X-ray powder diffraction (XRD) measurements. High purity nanocrystalline powders and small single crystals of Y1−xNdxAlO3 (0≤x≤1) have been produced successfully by modified sol–gel (Pechini) and micro-pulling-down methods, respectively. Both end members show high mutual solubility >25% in the solid phase, with a miscibility gap for intermediate compositions. A solid solution with x≈0.2 melts azeotropic ca. 20° below pure YAP. Such crystals can be grown from the melt without segregation. The narrow solid/liquid region near the azeotrope point could be measured with a “cycling” DTA measurement technique.

Journal of nanoscience and nanotechnology, 2009

Spectroscopic features of Eu3+, Nd3+ and Er3+ in nanocrystalline samples of gallium gadolinium ga... more Spectroscopic features of Eu3+, Nd3+ and Er3+ in nanocrystalline samples of gallium gadolinium garnet prepared by a modified sol-gel method were investigated in order to assess the structural compatibility of the material with a single crystal counterpart. Emission spectra and decay curves of luminescent admixtures were recorded and analysed. Observed distribution of spectral line intensities and single exponential time dependence of luminescence decay curves indicate strongly that the static disorder in the neighbourhood of luminescent ions is not significant, hence structural peculiarities of the garnet lattice encountered in bulk crystals are maintained. It has been concluded that the method of preparation applied is able to furnish good structural quality GGG nanocrystals.

Optical Materials, 2009

The nanocrystalline powders of Y 4 Al 2 O 9 single doped with Nd 3+ , Yb 3+ , Er 3+ and co-doped ... more The nanocrystalline powders of Y 4 Al 2 O 9 single doped with Nd 3+ , Yb 3+ , Er 3+ and co-doped with Nd 3+ and Yb 3+ as well as with Yb 3+ and Er 3+ were obtained by a modified sol-gel method starting from nitrates and acetates rather than citrates. The powders were characterised by X-ray diffraction method, high resolution scanning electron microscopy and luminescence spectroscopy. Close similarity of low temperature emission spectra recorded for Y 4 Al 2 O 9 nanocrystalline powder doped with Nd 3+ and for a single crystal counterpart grown by the micro-pulling technique implies that the sol-gel method applied is able to provide material in which the structural peculiarities encountered in bulk crystals are maintained. Efficiency of nonradiative energy transfer between rare earth ions was assessed based on analysis of luminescence decay curves. It has been concluded that the Y 4 Al 2 O 9 host may be promising for the design of multiple doped phosphors whose emission characteristics are tailored by energy transfer between properly chosen activators.

Materials Research Bulletin, 2009

ABSTRACT Structure, morphology and luminescence properties of nanocrystalline samples of YAl3(BO3... more ABSTRACT Structure, morphology and luminescence properties of nanocrystalline samples of YAl3(BO3)4 (YAB) undoped and doped with neodymium, ytterbium and chromium obtained by the sol–gel method are presented. The best results of synthesis are obtained for mannitol as polymerizing agent. Single phase of nanopowder is obtained for pure YAB. Dopants destroy the compound structure; two other compounds, namely Al18B4O33 and YBO3, were revealed by X-ray investigation. Nanopowders show isometric and needles forms, the calculated size of crystallites is about 60nm. Their optical properties are determined and results are compared to data obtained for single crystal counterparts. It is shown that the influence of rare earth ions incorporated into YBO3 phase on luminescent spectra and excited state relaxation dynamics of the nanopowders is negligibly small when the YBO3 content is of the order of several wt%. Residual impurity phases do not affect significantly spectroscopic properties of YAB nanopowders.

Materials Research Bulletin, 2011

Journal of Alloys and Compounds, 2011

a b s t r a c t YAG:Nd powders obtained by grinding a single crystal and synthesized by modified ... more a b s t r a c t YAG:Nd powders obtained by grinding a single crystal and synthesized by modified sol-gel and combustion methods were embedded at the stage of melting in a multicomponent borate glass to obtain luminescent glass-ceramic systems. Room temperature optical absorption spectra, luminescence spectra at room temperature and at 10 K and micro-Raman spectra were recorded to determine the location of Nd 3+ ions in composite materials. It has been concluded that their luminescence characteristics depend critically on the preparation method hence the morphology of precursor crystalline YAG:Nd powders as a consequence of dissimilar solubility of crystallites in a host glass.

Journal of Alloys and Compounds, 2011

The binary phase diagram of the YAlO 3 (YAP) -NdAlO 3 (NAP) system was determined by differential... more The binary phase diagram of the YAlO 3 (YAP) -NdAlO 3 (NAP) system was determined by differential thermal analysis (DTA) and X-ray powder diffraction (XRD) measurements. High purity nanocrystalline powders and small single crystals of Y 1-x Nd x AlO 3 (0 ≤ x ≤1) have been produced successfully by modified sol-gel (Pechini) and micro-pulling-down methods, respectively. Both end members show high mutual solubility > 25% in the solid phase, with a miscibility gap for intermediate compositions. A solid solution with x ≈ 0.2 melts azeotropic ca. 20 degrees below pure YAP. Such crystals can be grown from the melt without segregation. The narrow solid/liquid region near the azeotrope point could be measured with a "cycling" DTA measurement technique.

Crystal Research and Technology, 2007

Single crystals of GdCa 4 O(BO 3 ) 3 (GdCOB) pure and doped with Eu concentration of 1 and 4 at% ... more Single crystals of GdCa 4 O(BO 3 ) 3 (GdCOB) pure and doped with Eu concentration of 1 and 4 at% were grown by the Czochralski and micropulling-down methods. The distribution of Eu ions in GdCOB crystals was uniform. The substitutions of Eu 3+ in Gd, Ca(1) and Ca(2) cation sites and eventually formation Eu 2+ have been investigated. The spectroscopic properties of crystals are compared with the properties of nanopowders obtained by sol-gel method. Radioluminescence spectra of undoped GdCOB crystal show the characteristic emission of Gd 3+ at about 312 nm, whereas this emission dramatically decreases in Eu-doped crystals upon X-ray excitation, as well as in Eu-doped nanopowders excited in vacuum ultraviolet (VUV) region. The VUV excitation in the range 125-333 nm for Eu-doped samples leads to strong emission in red coming from the 5 D 0 multiplet of Eu 3+ , only. In the photoluminescence decay kinetics of 312 nm emissions substantial shortening and departure for single exponential decay in Eu-doped samples is clearly observed. Higher Eu doping results in further acceleration of the decay. In undoped GdCOB crystal, the lifetime of the Gd 3+ 6 P 7/2 multiplet is 2.79 ms. The Eu 3+ 5 D 0 decay kinetics monitored at 613 nm are rather constant. Numerical fitting of fully exponential curves, reveals lifetimes 2.7 ms for nanopowder and 2.5 ms for single crystal. The results suggest that this material may be used as a red phosphor in plasma display panels in nanopowder form because of strong excitation band of Eu 3+ luminescence in the 160-200 nm regions. Contrary to nanopowder sample, such an excitation band, attributed to the Gd 3+ -O 2charge transfer was not observed in crystal obtained by the micropulling-down method.

Crystal Research and Technology, 2007

Nanopowders of Y 2 O 3 pure, doped and codoped by Nd 3+ , Yb 3+ were obtained by sol-gel method. ... more Nanopowders of Y 2 O 3 pure, doped and codoped by Nd 3+ , Yb 3+ were obtained by sol-gel method. Solution with ethylene glycol was choosed as the proper solution where crystallites of powder with Nd and Yb dopants had the same size. Finally the one-phased compounds of Y 2 O 3 doped 0.5 at% Nd and 1, 2 or 4 at% Yb were obtained. Grain growth and their morphology were investigated in various temperature and time of heating. The changes of crystallite sizes and lattice constants in relation to the heating time and temperature for the composition Y 2 O 3 doped 0.5 at% Nd and 2 at% Yb are presented. Y 2 O 3 containing 0,5 at% of Nd exhibits intense luminescence bands centered at 920 nm, 1100 nm and 1360 nm whereas a single band at about 1020 nm appears in samples co-doped with neodymium and ytterbium. Luminescence spectra recorded did not depend on the sample preparation procedure and size of grains. OH impurity affects critically the relaxation dynamics of luminescent ion in nanopowders.

Crystal Research and Technology, 2009

The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neo... more The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neodymium were investigated. Nanopowders of GGG:Nd were prepared by modified sol-gel method using acetic acid as complexing agent. This way permitted to incorporate large amounts of dopant (up to 10 %) without destroying garnet structure. Small single crystals of Nd:GGG were grown by a µ-pulling down method and spectroscopic features of nanopowders and their single crystal counterparts were compared. It has concluded that the Nd 3+ ions are located preferentially in the same type of sites in crystal lattices of GGG:Nd nanopowders and their single crystal counterparts. In addition, it follows from the perfect agreement of emission wavelengths and line width recorded for nanopowders and single crystal samples that the crystal lattice of GGG in nanopowders is not distorted.

The XRD, XPS, SEM and magnetic characterization of the nano and single crystals SrLaAlO 4 doped w... more The XRD, XPS, SEM and magnetic characterization of the nano and single crystals SrLaAlO 4 doped with Mn were done. The sol-gel method was used to obtain the nanopowder and SEM imaging confirmed the submicron size of grains. The single crystals were grown by the Czochralski method. All compounds exhibit excess of strontium and deficiency of aluminium. The unit cell volumes increase with the amount of strontium. The electronic structures measured by XPS of the undoped yellowish single crystals and those nominally doped with 0.02 Mn (amber) and 0.1 Mn (olive) are very similar with comparable ratios of the main to the additional lines. It differs in the case of the nanocrystals, where the surface decomposition is observed. The magnetic measurements indicate the presence of the Mn 4+ ions and are in good agreement with the spectroscopic data.

Crystal Research and Technology, 2009

ABSTRACT The nanocrystalline powders of Y4Al2O9 (YAM) pure and doped by Nd, Yb and codoped by Nd ... more ABSTRACT The nanocrystalline powders of Y4Al2O9 (YAM) pure and doped by Nd, Yb and codoped by Nd and Yb were obtained via modified sol-gel method. These powders were characterized by X-ray diffraction method, scanning electron microscopy and high resolution scanning electron microscopy, luminescence spectroscopy and differential thermal analysis (DTA). We obtained single phase powders of crystalline structure with average size 70 nm exhibiting interesting luminescent properties. Efficient non-radiative energy transfer between Nd and Yb was found. DTA confirmed the phase transition at about 1400 °C. From these nanocrystalline powders, the crystals YAM:Yb, YAM:Yb,Nd were grown by micro-pulling down technique. They were cracking during cooling owing to the phase transition. Luminescent properties of YAM:Nd,Yb crystals were identical with properties of corresponding nanopowders within experimental incertitude. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)