Search

LiFeP2O7and Li0.9Fe0.9Ti0.1P2O7were synthesised by solid-state reaction and ceramics were sintered. The structure of compounds was studied in the temperature range 300–700 K by X-ray diffraction. Ceramics’ surfaces were investigated by scanning electron microscope. Binding energies of Fe 2p, P 2p and O 1s core levels at ceramics’ surfaces have been determined by X-ray photoelectron spectroscopy and different valence states of Fe and P were detected. Elemental compositions of the compounds were studied by energy dispersive X-ray spectrometer. Impedance spectroscopy was performed in the frequency range 10 Hz–3 GHz and in the temperature interval 400–700 K. The changes of the activation energy of ionic conductivity at 528 and 550 K for LiFeP2O7and Li0.9Fe0.9Ti0.1P2O7, respectively, were found. The phenomena can be related to disordering in the unit cells of the compounds. [ABSTRACT FROM AUTHOR]

Copyright of Lithuanian Journal of Physics is the property of Lithuanian Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lithuanian Journal of Physics is the property of Lithuanian Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

At room temperature solid electrolyte Li3−xSc2−xZrx(PO4)3 (x = 0, 0.1) compounds belong to monoclinic symmetry (space group P21/n) and the compound with x = 0.2 belongs to orthorhombic symmetry (Pbcn). At 900 K all the investigated compounds belong to orthorhombic symmetry (space group Pbcn). Anomalies of enthalpy, change of activation energy of ionic conductivity, anomalies of dielectric permittivity in the temperature range 420 K–660 K of investigated compounds with x = 0 and 0.1 were found. The phenomena are related to structure phase transition in the compounds. The relaxation dispersion regions were found in conductivity spectra for the all investigated samples. The frequency dispersion regions are caused by the relaxation processes in grain, grain – boundaries and electrodes. The temperature dependencies of the bulk conductivity and relaxation frequency in the bulk are governed by the same activation energy. It is shown that major role in the temperature dependence of bulk conductivity is played by Li+ ion mobility, which increases as temperature increases. [ABSTRACT FROM PUBLISHER]

The solid electrolyte Li2.9Sc1.9-yYyZr0.1(PO4)3 (where y = 0, 0.1) compounds belong to monoclinic symmetry (space group P21/n) at room temperature. The Zr 3d, Sc 2p, P 2p, Y 3d, O 1s, and Li 1s core level X-ray photoelectron spectra (XPS) were fitted. The Li ions in ceramics without Y occupy two different positions and in the ceramics with Y they occupy one position in the lattice. The deconvolutions of the Zr 3d, P 2p, Sc 2p, and Y 3d core level XPS are associated with different valence states on the surfaces of the investigated ceramics. Anomalies of enthalpy, change of activation energy of ionic conductivity, anomalies of dielectric permittivity in the temperature range 420-520 K of investigated compounds were found. The phenomena are related to diffuse structure phase transition in the compounds. At temperatures 600 and 900 K, the compounds belong to orthorhombic symmetry (space group Pbcn). [ABSTRACT FROM AUTHOR]

Abstract: The powders of Li1+y Ge2−x−y Ti x Al y (PO4)3 (x =0.1÷0.3, y =0.07÷0.21) have been synthesized by a solid phase reaction. The structure of the compounds was determined by X-ray diffraction patterns from the powder. The compounds belong to the rhombohedral symmetry (s. g. R3¯c) with six formula units in the lattice. The sintering of the Li1+y Ge2−x−y Ti x Al y (PO4)3 ceramics was conducted at temperature T =1363 K for 1 h in air. The ionic conductivity of the ceramics was investigated by impedance spectroscopy in the frequency range from 1 MHz to 1.2 GHz at temperatures from 300 K to 600 K. Two dispersions regions were found in ionic conductivity spectra for all the compounds. The dispersions are caused by the ion transport in grain boundaries and in grains of the ceramic samples. The substitution of Ge4+ →Ti4+, Al3+ leads to the changes in the structure parameters and electrical properties of the compounds. [Copyright &y& Elsevier]

Abstract: The solid electrolyte Li1.3Zr1.4Ti0.3Al0.3(PO4)3 compound was synthesized by a solid-state reaction. The ceramic samples were sintered 1, 2 and 3h and studied by X-ray and complex impedance spectroscopy in the frequency range from 106 to 1.2×109 Hz in temperature range from 300 to 600K. The investigated compound at room temperature belongs to rhombohedral symmetry (s.g. ) with six formula units in the lattice. Two regions of relaxation dispersion were found. The dispersions are related to the fast Li+ ion transport in the grain and grain boundaries of ceramics. Varying of the sintering time affects the density of the ceramics, the values of total conductivity and its activation energy. The values of grain conductivity, its activation energy, and relaxation frequency in grain, dielectric permittivity and dielectric losses are independent from sintering duration of the ceramics. The value of activation energy of grain conductivity and activation energy of relaxation frequency is the same. That can be attributed to the fact that the temperature dependence of the grain conductivity is caused only by the mobility of Li+ ions, while a number of charge carriers remains constant with temperature. [Copyright &y& Elsevier]

Abstract: The powders of Li1.3Sc0.15Y0.15Ti1.7(PO4)3 were synthesized by a solid phase reaction. The sintering duration of the ceramic samples was varied from 0.25 h to 3 h and studied by X-ray and impedance spectroscopy in the frequency range from 10 Hz to 1.2×109 Hz at temperatures up to 600 K. Two relaxation dispersions of the electrical parameters were found and analysed in terms of bulk and grain boundary ionic transport processes. Varying of the sintering duration affects the density of the ceramics, sizes of grains, values of the total conductivity (σ t) and its activation energy (ΔE t). The bulk conductivity (σ b) and its activation energy (ΔE b) in average do not depend on duration of sintering. [Copyright &y& Elsevier]

The solid electrolyte Li1+2xMgxTi2−xP3O12 compounds were synthesized by a solid state reaction. The ceramic samples were sintered for 0.2, 0.5, 1 and 3 h and studied by X-ray and complex impedance spectroscopy in the frequency range 10 Hz–1.2 GHz in the temperature range 300–600 K. Two regions of relaxation dispersion were found, the dispersions were related to the fast Li+ ion transport in the bulk and grain boundaries. Varying of the sintering time affects the density, values of grain boundary conductivity (σgb), its activation energy (ΔEgb) and relaxation frequency (fgb). The activation energy (ΔEb) of bulk conductivity (σb) and activation energy (ΔEf) of relaxation frequency (fb) in the bulk are the same. That can be attributed to the fact that the temperature dependence of the bulk conductivity is caused only by the mobility of the fast Li+ ions, while a number of charge carriers remains constant with temperature. [Copyright &y& Elsevier]

Abstract: Li1.3AlyYx−yTi1.7(PO4)3 (x=0.3; y=0.1, 0.2) solid electrolyte compounds were synthesized by solid state reaction and studied by X-ray diffraction. At room temperature the compounds belong to a rhombohedral symmetry (space group Rc) with six formula units in the unit cell. Ti 2p, O 1s, P 2p, Li 1s, Y 3d, and Al 2p core level XP spectra at Li1.3AlyYx−yTi1.7(PO4)3 (x=0.3; y=0.1, 0.2) ceramic surfaces have been determined by XPS. The measurements of the electrical properties of the ceramic samples in the frequency range 10Hz–1MHz were carried out by a two probe method and a four probe method. The measurements in the microwave range (3·105–3·109 )Hz were performed in a coaxial line, the part of the inner conductor which was replaced by the sample. The investigation of the electrical properties of the ceramic samples was carried out in air in the temperature range (300 to 700)K. The increase of the stoichiometric factor y of the compounds leads to the increase in the total and bulk conductivities of ceramics and decreases their activation energies. [Copyright &y& Elsevier]