Abstract Amorphous hafnia (HfO 2 ) powders were synthesized through a novel reduction–oxidation r... more Abstract Amorphous hafnia (HfO 2 ) powders were synthesized through a novel reduction–oxidation route, in which, metal hafnium was reduced from hafnium tetrachloride (HfCl 4 ) by sodium borohydride (NaBH 4 ), and then oxidized in ambient atmosphere. Upon calcinations, the powder crystallized to nanometric size HfO 2 powder with monoclinic structure. Powder properties such as lattice parameters, crystallite and particle size were studied. X-ray diffraction analysis (XRD) was used to characterize structure and phase evolution in synthesized samples. Calculation of the average crystallite size ( D ) was performed on the basis of the full width at half maximum intensity (FWHM) of the XRD peaks. Williamson-Hall plots were used to separate the effect of the size and strain in the nanocrystals. The morphologies of powders calcinated at higher temperatures were followed by Scanning electron microscopy (SEM).
ABSTRACT a b s t r a c t Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x =... more ABSTRACT a b s t r a c t Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x = 0.1–0.5 were synthesized by using Self Propagating Room Temperature procedure (SPRT). The results obtained by XRPD show that synthe-sized samples were single-phase solid solution at room temperature. Powders were densified by using Conventional (CS) and Microwave (MS) Sintering techniques at different temperatures, in an air atmo-sphere for 1 h. Scanning electron microscopy (SEM) and complex impedance method measurements were carried out on sintered samples. Maximum achieved density was for sample with Ce 0.80 Bi 0.20 O 2Àd composition for both applied sintering techniques. The highest conductivity was obtained for the ceramic composition Ce 0.80 Bi 0.20 O 2Àd sintered by microwave technique at 700 °C. Ó 2014 Elsevier B.V. All rights reserved.
ABSTRACT With the increased interest in application of Li aluminosilicate materials as solid elec... more ABSTRACT With the increased interest in application of Li aluminosilicate materials as solid electrolytes, this study focuses on investigating the influence of structure on conductivity properties in single-crystal LiAlSi2O6 which is characterized by three crystal polymorphs where only structural arrangements differ while the amount of mobile carriers is identical. Two single-crystal polymorphic phases produced at ambient pressure are with tetragonal P41212 symmetry and hexagonal P6222 symmetry, also referred to as β- and γ-spodumene in the older literature. For this study, flux-grown hexagonal spodumene single-crystals were measured for conductivity parallel to the crystallographic c-axis and the results were compared with previously published results for tetragonal spodumene, both as single-crystal and polycrystalline aggregate, monoclinic spodumene (α-spodumene) and LiAlSi2O6 glass. The activation energy E a of 79.69 ± 0.38 kJ/mol for hexagonal phase is very similar to the other crystalline polymorphs with the same orientation. However, the σ DC in hexagonal spodumene was determined to be higher than other crystalline phases and about 1.5 orders of magnitude lower than the conductivity in glass LiAlSi2O6 phase. Additionally, the densities of atomic packing were compared between phases, and the differences in the openness of the structures indicate that the more dominant effect on the Li mobility lies with the actual spatial arrangement of Li sites and the Si/Al sublattice.
ABSTRACT Nanocrystalline powders of solid solution CeO2–Bi2O3 were synthesized by self-propagatin... more ABSTRACT Nanocrystalline powders of solid solution CeO2–Bi2O3 were synthesized by self-propagating room temperature reaction (SPRT) procedure with composition (Ce1−xBixO2−δ where the x = 0.1–0.5). X-ray diffraction analyses show that for x < 0.50 a solid solution with fluorite structure is formed. Rietveld's structure refinement method was applied to characterize prepared powders and its microstructure (size–strain). The lattice parameters increase according to Vegard's rule with increasing of Bi concentration. The average crystallite size is about 2–3 nm. Spectroscopic ellipsometry and Raman scattering measurements were used to characterize the samples at room temperature. The Raman measurements demonstrated electron molecular vibrational coupling and increase of oxygen vacancy concentration whereas increase of Bi content provokes a small decrease of optical absorption edge in comparison with pure ceria. Specific surface area of obtained powders was measured by Brunauer–Emmet–Teller (BET) method.
Monoclinic celsian has been prepared from Ba-LTA zeolite precursor. The Ca2+-exchanged hexacelsia... more Monoclinic celsian has been prepared from Ba-LTA zeolite precursor. The Ca2+-exchanged hexacelsian (HCCa) synthesized from Ba-LTA zeolite precursors was used for preparation of monoclinic celsian (MCCa). The partially ion exchange diphyllosilicate has a composition of Ba0.64Ca0.32Al2Si2O8 (HCCa). It was found that prepared HCCa phase is stable between room temperature and 1300°C. During prolonged heating this phase is polymorphic transformed to
Mechanical activation of precursors has been used for the preparation of Cr-doped sphene ceramic ... more Mechanical activation of precursors has been used for the preparation of Cr-doped sphene ceramic pigments (CaTi 1Ày Cr y SiO 5 ). Ceramic material has been prepared from a powder mixture of CaCO 3 , TiO 2 , SiO 2 and Cr(NO 3 )Á9H 2 O using vibro-milling for homogenization and activation of precursors. The mechanochemical process initially yielded amorphous powders, which on further calcination, crystallized to yield Cr-doped sphene ceramic pigment. Phase evolution in CaTi 1Ày Cr y SiO 5 composition with thermal treatment was investigated by X-ray powder diffraction (XRPD). Texture properties and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. UV/Vis reflectance spectra are used to determinate the behavior of the chromium ion. The color efficiency of pigments was evaluated by colorimetric analysis (CIE L à a à b system). Photoluminescence measurements were also performed.
Multidoped nanosized ceria powders were prepared by either modified glycine nitrate procedure (MG... more Multidoped nanosized ceria powders were prepared by either modified glycine nitrate procedure (MGNP) or self-propagating reaction at room temperature (SPRT). As the dopants to CeO 2 , trivalent rare earth oxides such as Nd 2 O 3 , Sm 2 O 3 , Gd 2 O 3 , Dy 2 O 3 and Y 2 O 3 were used, with the total molar fraction of 20%. The pressed powder pellets were subjected to the densification by sintering at 1500 1C, in an air atmosphere. A single-phase crystalline form was evidenced by X-ray diffractometry for both sintered materials. By means of complex impedance measurements, the conductivity of the sintered samples was determined as a function of temperature. At 700 1C, the conductivity amounted to 2.19 Â 10 À 2 and 1.40 Â 10 À 2 Ω À 1 cm À 1 for the SPRT and for the MGNP sample, respectively. The corresponding values of activation energies of conductivity amounted to 0.72 (MGNP) and 0.59 (SPRT) eV in the temperature range 550–700 1C.
Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x = 0.1–0.5 were synthesized... more Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x = 0.1–0.5 were synthesized by using Self Propagating Room Temperature procedure (SPRT). The results obtained by XRPD show that synthesized samples were single-phase solid solution at room temperature. Powders were densified by using Conventional (CS) and Microwave (MS) Sintering techniques at different temperatures, in an air atmosphere for 1 h. Scanning electron microscopy (SEM) and complex impedance method measurements were carried out on sintered samples. Maximum achieved density was for sample with Ce 0.80 Bi 0.20 O 2Àd composition for both applied sintering techniques. The highest conductivity was obtained for the ceramic composition Ce 0.80 Bi 0.20 O 2Àd sintered by microwave technique at 700 °C.
Fine tungsten carbide (WC) powder was prepared by solid state reaction between tungsten powder (W... more Fine tungsten carbide (WC) powder was prepared by solid state reaction between tungsten powder (W) and activated carbon cloth as a new carbon (C) source. The effect of temperature and time of heat treatment as well as the effect of C/W ratio on WC phase formation was studied. The results obtained by X-ray powder diffraction (XRPD) show that obtained powder is single WC. Microstructure and morphology was determinate by means of scanning electron microscopy (SEM). Brunauer–Emmett–Teller (BET) method was used for examining specific surface area and texture of obtained powders. It was found that WC powder was successfully synthesized in excess carbon after eight-hour heat treatment at relatively low temperature (1000 1C).
indicate that the more dominant effect on the Li mobility lies with the actual spatial arrangemen... more indicate that the more dominant effect on the Li mobility lies with the actual spatial arrangement of Li sites and the Si/Al sublattice.
A novel method for synthesis of carbon cryogel/zeolite composites was obtained. Method considers ... more A novel method for synthesis of carbon cryogel/zeolite composites was obtained. Method considers forming of carbon cryogel from the sol-gel polycondenzation of resorcinol and formaldehyde, followed by freeze drying, and subsequent pyrolysis in presence of different amount of zeolite. Characterization of composite materials by nitrogen adsorption shows that samples are micro-and mesoporous and that specific surface area decrease with increasing the amount of zeolite in samples. XRD method confirms amorphous structure of carbon cryogel and crystalline structure of zeolite, i.e. structure of zeolite has not been destroyed by carbonization process. SEM and EDX analyses reveal homogenous distribution of zeolite through out carbon cryogel and corresponding composition.
Ce 1Àx Pr x O 2Àd (0 # x # 0.4) nanocrystals were synthesized by self-propagating method and thor... more Ce 1Àx Pr x O 2Àd (0 # x # 0.4) nanocrystals were synthesized by self-propagating method and thoroughly characterized using X-ray diffraction, Raman and X-ray photoelectron spectroscopy and magnetic measurements. Undoped CeO 2 nanocrystals exhibited intrinsic ferromagnetism at room temperature. Despite the increased concentration of oxygen vacancies in doped samples, our results showed that ferromagnetic ordering rapidly degrades with Pr doping. The suppression of ferromagnetism can be explained in terms of the different dopant valence state, the different nature of the vacancies formed in Pr-doped samples and their ability/disability to establish the ferromagnetic ordering.
Nanometric Bi2O3 powder was successfully synthesized by applying the method based on self-propaga... more Nanometric Bi2O3 powder was successfully synthesized by applying the method based on self-propagating room temperature reaction (SPRT) between bismuth nitrates and sodium hydroxide. X-ray powder diffraction (XRPD) and Rietveld's structure refinement method were applied to characterize prepared powder. It revealed that synthesized material is a single phase monoclinic α-Bi2O3 (space group P21/c with cell parameters a=5.84605(4)Å, b=8.16339(6) Å, c=7.50788(6) Å
Single phase solid solution Ce 1Àx Bi x O 2Àd with the composition of x = 0.1-0.5 were successful... more Single phase solid solution Ce 1Àx Bi x O 2Àd with the composition of x = 0.1-0.5 were successfully synthesized at room temperature using simple and fast Self Propagating Room Temperature procedure (SPRT). Thermal stability of these solid solutions with different concentration of Bi cation was investigated at various temperatures up to 1400°C by applying thermogravimetric analysis (DTA/DTG/TG). Powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Infra Red spectroscopy (IR). It was revealed that all samples with concentration of bismuth higher than 10 at.% are unstable during thermal treatment, resulting in Bi leaving the structure of ceria and formation of b-Bi 2 O 3 as second phase. Moreover, at a certain temperatures bismuth begins to evaporate.
A coordination polymer, {Mn(H 2 O) 2 [NiCN] 4 Á 4H 2 O} n , showed that the coordination layers a... more A coordination polymer, {Mn(H 2 O) 2 [NiCN] 4 Á 4H 2 O} n , showed that the coordination layers are stacked on top of each other sandwiching 2D ice layer of boat-shaped hexagonal water clusters.
ABSTRACT Multidoped nanosized ceria powders were prepared by either modified glycine nitrate proc... more ABSTRACT Multidoped nanosized ceria powders were prepared by either modified glycine nitrate procedure (MGNP) or self-propagating reaction at room temperature (SPRT). As the dopants to CeO2, trivalent rare earth oxides such as Nd2O3, Sm2O3, Gd2O 3, Dy2O3 and Y2O3 were used, with the total molar fraction of 20%. The pressed powder pellets were subjected to the densification by sintering at 1500 °C, in an air atmosphere. A single-phase crystalline form was evidenced by X-ray diffractometry for both sintered materials. By means of complex impedance measurements, the conductivity of the sintered samples was determined as a function of temperature. At 700 °C, the conductivity amounted to 2.19×10-2 and 1.40×10-2 Ω-1 cm-1 for the SPRT and for the MGNP sample, respectively. The corresponding values of activation energies of conductivity amounted to 0.72 (MGNP) and 0.59 (SPRT) eV in the temperature range 550-700 °C.
ABSTRACT Amorphous Pr6O11 powder was obtained by applying self-propagating room temperature metho... more ABSTRACT Amorphous Pr6O11 powder was obtained by applying self-propagating room temperature method (SPRT). After calcination, the amorphous powder converted to nanometric Pr6O11 powder with cubic fluorite-type structure. Powder properties such as crystallite size, lattice strain and lattice parameter were studied by X-ray diffraction (XRD) at room temperature. The crystallite size was estimated by means of the full width at half maxima (FWHM) of XRD peaks. Williamson–Hall plots were used to determine the lattice strain whereas the Ritveld analysis was employed for crystal structure refinement. It was found that the powder properties are affected by both calcination temperature and duration of thermal treatment. The crystallite size varied from 5 to ∼250 nm, whereas the lattice parameter varied from 5.461 to 5.494 Å. The powder obtained after four-hour long calcination was almost free of internal strain.
Abstract Amorphous hafnia (HfO 2 ) powders were synthesized through a novel reduction–oxidation r... more Abstract Amorphous hafnia (HfO 2 ) powders were synthesized through a novel reduction–oxidation route, in which, metal hafnium was reduced from hafnium tetrachloride (HfCl 4 ) by sodium borohydride (NaBH 4 ), and then oxidized in ambient atmosphere. Upon calcinations, the powder crystallized to nanometric size HfO 2 powder with monoclinic structure. Powder properties such as lattice parameters, crystallite and particle size were studied. X-ray diffraction analysis (XRD) was used to characterize structure and phase evolution in synthesized samples. Calculation of the average crystallite size ( D ) was performed on the basis of the full width at half maximum intensity (FWHM) of the XRD peaks. Williamson-Hall plots were used to separate the effect of the size and strain in the nanocrystals. The morphologies of powders calcinated at higher temperatures were followed by Scanning electron microscopy (SEM).
ABSTRACT a b s t r a c t Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x =... more ABSTRACT a b s t r a c t Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x = 0.1–0.5 were synthesized by using Self Propagating Room Temperature procedure (SPRT). The results obtained by XRPD show that synthe-sized samples were single-phase solid solution at room temperature. Powders were densified by using Conventional (CS) and Microwave (MS) Sintering techniques at different temperatures, in an air atmo-sphere for 1 h. Scanning electron microscopy (SEM) and complex impedance method measurements were carried out on sintered samples. Maximum achieved density was for sample with Ce 0.80 Bi 0.20 O 2Àd composition for both applied sintering techniques. The highest conductivity was obtained for the ceramic composition Ce 0.80 Bi 0.20 O 2Àd sintered by microwave technique at 700 °C. Ó 2014 Elsevier B.V. All rights reserved.
ABSTRACT With the increased interest in application of Li aluminosilicate materials as solid elec... more ABSTRACT With the increased interest in application of Li aluminosilicate materials as solid electrolytes, this study focuses on investigating the influence of structure on conductivity properties in single-crystal LiAlSi2O6 which is characterized by three crystal polymorphs where only structural arrangements differ while the amount of mobile carriers is identical. Two single-crystal polymorphic phases produced at ambient pressure are with tetragonal P41212 symmetry and hexagonal P6222 symmetry, also referred to as β- and γ-spodumene in the older literature. For this study, flux-grown hexagonal spodumene single-crystals were measured for conductivity parallel to the crystallographic c-axis and the results were compared with previously published results for tetragonal spodumene, both as single-crystal and polycrystalline aggregate, monoclinic spodumene (α-spodumene) and LiAlSi2O6 glass. The activation energy E a of 79.69 ± 0.38 kJ/mol for hexagonal phase is very similar to the other crystalline polymorphs with the same orientation. However, the σ DC in hexagonal spodumene was determined to be higher than other crystalline phases and about 1.5 orders of magnitude lower than the conductivity in glass LiAlSi2O6 phase. Additionally, the densities of atomic packing were compared between phases, and the differences in the openness of the structures indicate that the more dominant effect on the Li mobility lies with the actual spatial arrangement of Li sites and the Si/Al sublattice.
ABSTRACT Nanocrystalline powders of solid solution CeO2–Bi2O3 were synthesized by self-propagatin... more ABSTRACT Nanocrystalline powders of solid solution CeO2–Bi2O3 were synthesized by self-propagating room temperature reaction (SPRT) procedure with composition (Ce1−xBixO2−δ where the x = 0.1–0.5). X-ray diffraction analyses show that for x < 0.50 a solid solution with fluorite structure is formed. Rietveld's structure refinement method was applied to characterize prepared powders and its microstructure (size–strain). The lattice parameters increase according to Vegard's rule with increasing of Bi concentration. The average crystallite size is about 2–3 nm. Spectroscopic ellipsometry and Raman scattering measurements were used to characterize the samples at room temperature. The Raman measurements demonstrated electron molecular vibrational coupling and increase of oxygen vacancy concentration whereas increase of Bi content provokes a small decrease of optical absorption edge in comparison with pure ceria. Specific surface area of obtained powders was measured by Brunauer–Emmet–Teller (BET) method.
Monoclinic celsian has been prepared from Ba-LTA zeolite precursor. The Ca2+-exchanged hexacelsia... more Monoclinic celsian has been prepared from Ba-LTA zeolite precursor. The Ca2+-exchanged hexacelsian (HCCa) synthesized from Ba-LTA zeolite precursors was used for preparation of monoclinic celsian (MCCa). The partially ion exchange diphyllosilicate has a composition of Ba0.64Ca0.32Al2Si2O8 (HCCa). It was found that prepared HCCa phase is stable between room temperature and 1300°C. During prolonged heating this phase is polymorphic transformed to
Mechanical activation of precursors has been used for the preparation of Cr-doped sphene ceramic ... more Mechanical activation of precursors has been used for the preparation of Cr-doped sphene ceramic pigments (CaTi 1Ày Cr y SiO 5 ). Ceramic material has been prepared from a powder mixture of CaCO 3 , TiO 2 , SiO 2 and Cr(NO 3 )Á9H 2 O using vibro-milling for homogenization and activation of precursors. The mechanochemical process initially yielded amorphous powders, which on further calcination, crystallized to yield Cr-doped sphene ceramic pigment. Phase evolution in CaTi 1Ày Cr y SiO 5 composition with thermal treatment was investigated by X-ray powder diffraction (XRPD). Texture properties and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. UV/Vis reflectance spectra are used to determinate the behavior of the chromium ion. The color efficiency of pigments was evaluated by colorimetric analysis (CIE L à a à b system). Photoluminescence measurements were also performed.
Multidoped nanosized ceria powders were prepared by either modified glycine nitrate procedure (MG... more Multidoped nanosized ceria powders were prepared by either modified glycine nitrate procedure (MGNP) or self-propagating reaction at room temperature (SPRT). As the dopants to CeO 2 , trivalent rare earth oxides such as Nd 2 O 3 , Sm 2 O 3 , Gd 2 O 3 , Dy 2 O 3 and Y 2 O 3 were used, with the total molar fraction of 20%. The pressed powder pellets were subjected to the densification by sintering at 1500 1C, in an air atmosphere. A single-phase crystalline form was evidenced by X-ray diffractometry for both sintered materials. By means of complex impedance measurements, the conductivity of the sintered samples was determined as a function of temperature. At 700 1C, the conductivity amounted to 2.19 Â 10 À 2 and 1.40 Â 10 À 2 Ω À 1 cm À 1 for the SPRT and for the MGNP sample, respectively. The corresponding values of activation energies of conductivity amounted to 0.72 (MGNP) and 0.59 (SPRT) eV in the temperature range 550–700 1C.
Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x = 0.1–0.5 were synthesized... more Solid solution Ce 1Àx Bi x O 2Àd nanopowders with the composition of x = 0.1–0.5 were synthesized by using Self Propagating Room Temperature procedure (SPRT). The results obtained by XRPD show that synthesized samples were single-phase solid solution at room temperature. Powders were densified by using Conventional (CS) and Microwave (MS) Sintering techniques at different temperatures, in an air atmosphere for 1 h. Scanning electron microscopy (SEM) and complex impedance method measurements were carried out on sintered samples. Maximum achieved density was for sample with Ce 0.80 Bi 0.20 O 2Àd composition for both applied sintering techniques. The highest conductivity was obtained for the ceramic composition Ce 0.80 Bi 0.20 O 2Àd sintered by microwave technique at 700 °C.
Fine tungsten carbide (WC) powder was prepared by solid state reaction between tungsten powder (W... more Fine tungsten carbide (WC) powder was prepared by solid state reaction between tungsten powder (W) and activated carbon cloth as a new carbon (C) source. The effect of temperature and time of heat treatment as well as the effect of C/W ratio on WC phase formation was studied. The results obtained by X-ray powder diffraction (XRPD) show that obtained powder is single WC. Microstructure and morphology was determinate by means of scanning electron microscopy (SEM). Brunauer–Emmett–Teller (BET) method was used for examining specific surface area and texture of obtained powders. It was found that WC powder was successfully synthesized in excess carbon after eight-hour heat treatment at relatively low temperature (1000 1C).
indicate that the more dominant effect on the Li mobility lies with the actual spatial arrangemen... more indicate that the more dominant effect on the Li mobility lies with the actual spatial arrangement of Li sites and the Si/Al sublattice.
A novel method for synthesis of carbon cryogel/zeolite composites was obtained. Method considers ... more A novel method for synthesis of carbon cryogel/zeolite composites was obtained. Method considers forming of carbon cryogel from the sol-gel polycondenzation of resorcinol and formaldehyde, followed by freeze drying, and subsequent pyrolysis in presence of different amount of zeolite. Characterization of composite materials by nitrogen adsorption shows that samples are micro-and mesoporous and that specific surface area decrease with increasing the amount of zeolite in samples. XRD method confirms amorphous structure of carbon cryogel and crystalline structure of zeolite, i.e. structure of zeolite has not been destroyed by carbonization process. SEM and EDX analyses reveal homogenous distribution of zeolite through out carbon cryogel and corresponding composition.
Ce 1Àx Pr x O 2Àd (0 # x # 0.4) nanocrystals were synthesized by self-propagating method and thor... more Ce 1Àx Pr x O 2Àd (0 # x # 0.4) nanocrystals were synthesized by self-propagating method and thoroughly characterized using X-ray diffraction, Raman and X-ray photoelectron spectroscopy and magnetic measurements. Undoped CeO 2 nanocrystals exhibited intrinsic ferromagnetism at room temperature. Despite the increased concentration of oxygen vacancies in doped samples, our results showed that ferromagnetic ordering rapidly degrades with Pr doping. The suppression of ferromagnetism can be explained in terms of the different dopant valence state, the different nature of the vacancies formed in Pr-doped samples and their ability/disability to establish the ferromagnetic ordering.
Nanometric Bi2O3 powder was successfully synthesized by applying the method based on self-propaga... more Nanometric Bi2O3 powder was successfully synthesized by applying the method based on self-propagating room temperature reaction (SPRT) between bismuth nitrates and sodium hydroxide. X-ray powder diffraction (XRPD) and Rietveld's structure refinement method were applied to characterize prepared powder. It revealed that synthesized material is a single phase monoclinic α-Bi2O3 (space group P21/c with cell parameters a=5.84605(4)Å, b=8.16339(6) Å, c=7.50788(6) Å
Single phase solid solution Ce 1Àx Bi x O 2Àd with the composition of x = 0.1-0.5 were successful... more Single phase solid solution Ce 1Àx Bi x O 2Àd with the composition of x = 0.1-0.5 were successfully synthesized at room temperature using simple and fast Self Propagating Room Temperature procedure (SPRT). Thermal stability of these solid solutions with different concentration of Bi cation was investigated at various temperatures up to 1400°C by applying thermogravimetric analysis (DTA/DTG/TG). Powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Infra Red spectroscopy (IR). It was revealed that all samples with concentration of bismuth higher than 10 at.% are unstable during thermal treatment, resulting in Bi leaving the structure of ceria and formation of b-Bi 2 O 3 as second phase. Moreover, at a certain temperatures bismuth begins to evaporate.
A coordination polymer, {Mn(H 2 O) 2 [NiCN] 4 Á 4H 2 O} n , showed that the coordination layers a... more A coordination polymer, {Mn(H 2 O) 2 [NiCN] 4 Á 4H 2 O} n , showed that the coordination layers are stacked on top of each other sandwiching 2D ice layer of boat-shaped hexagonal water clusters.
ABSTRACT Multidoped nanosized ceria powders were prepared by either modified glycine nitrate proc... more ABSTRACT Multidoped nanosized ceria powders were prepared by either modified glycine nitrate procedure (MGNP) or self-propagating reaction at room temperature (SPRT). As the dopants to CeO2, trivalent rare earth oxides such as Nd2O3, Sm2O3, Gd2O 3, Dy2O3 and Y2O3 were used, with the total molar fraction of 20%. The pressed powder pellets were subjected to the densification by sintering at 1500 °C, in an air atmosphere. A single-phase crystalline form was evidenced by X-ray diffractometry for both sintered materials. By means of complex impedance measurements, the conductivity of the sintered samples was determined as a function of temperature. At 700 °C, the conductivity amounted to 2.19×10-2 and 1.40×10-2 Ω-1 cm-1 for the SPRT and for the MGNP sample, respectively. The corresponding values of activation energies of conductivity amounted to 0.72 (MGNP) and 0.59 (SPRT) eV in the temperature range 550-700 °C.
ABSTRACT Amorphous Pr6O11 powder was obtained by applying self-propagating room temperature metho... more ABSTRACT Amorphous Pr6O11 powder was obtained by applying self-propagating room temperature method (SPRT). After calcination, the amorphous powder converted to nanometric Pr6O11 powder with cubic fluorite-type structure. Powder properties such as crystallite size, lattice strain and lattice parameter were studied by X-ray diffraction (XRD) at room temperature. The crystallite size was estimated by means of the full width at half maxima (FWHM) of XRD peaks. Williamson–Hall plots were used to determine the lattice strain whereas the Ritveld analysis was employed for crystal structure refinement. It was found that the powder properties are affected by both calcination temperature and duration of thermal treatment. The crystallite size varied from 5 to ∼250 nm, whereas the lattice parameter varied from 5.461 to 5.494 Å. The powder obtained after four-hour long calcination was almost free of internal strain.
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Papers by M. Prekajski