Effect of intergranular glass films on the electrical conductivity of 3Y-TZP

The electrical conductivity of 3Y-TZP ceramics containing SiO2 and Al2O3 has been investigated by complex impedance spectroscopy between 500 and 1270 K. At low temperatures, the total electrical conductivity is suppressed by the grain boundary glass films. The equilibrium thickness of intergranular films is 1-2 nm, as derived using the "brick-layer” model and measured by HRTEM. A change in the slope of the conductivity Arrhenius plots occurs at the characteristic temperature Tb at which the macroscopic grain boundary resistivity has the same value as the resistivity of the grains. The temperature dependence of the conductivity is discussed in terms of a series combination of RC element

Influence of cation substitution on electrical conductivity and optical absorption edge in Cu₇(Ge1–xSix)S₅I mixed crystals

Electrical conductivity of Cu₇(Ge₁₋xSix)S₅I mixed crystals was measured in the frequency range 1.0x10⁶ –1.2x10⁹ Hz and in the temperature interval 100–300 K. The frequency and temperature behaviour of the electrical conductivity were analyzed. The optical absorption edge of Cu₇(Ge₁₋xSix)S₅I mixed crystals within the temperature range 77–300 K was studied. The compositional dependences of the electrical conductivity, activation energy, optical pseudogap and Urbach energy were obtained. The influence of Ge→Si cation substitution on the optical absorption processes in the Cu₇(Ge₁₋xSix)S₅I mixed crystals is investigated

Broadband impedance spectroscopy of some Li+ and Vo** conducting solid electrolytes

The solid electrolyte Li3Ti1.5(PO4)3 compound has been synthesized by solid state reaction and studied by X-ray diffraction. At room temperature the compound belongs to rhombohedral symmetry (space group R3 ̅c) with six formula units in the unit cell. Li3Ti1.5(PO4)3, Li3xLa2/3–xTiO3 (where x = 0.12) Li+-ion conducting, Ce0.8Gd0.2O1.9, (ZrO2)92(Y2O3)8 with fast oxygen vacancy transport ceramic samples were investigated in the frequency range from 1 Hz to 3 GHz in the temperature interval (300-700) K by impedance spectroscopy methods. Two dispersion regions in ionic conductivity spectra for investigated ceramic samples have been found. The dispersions have been attributed to relaxation processes in grain boundaries and in grains of the ceramics

Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites

Complex dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x (x = 0.3−0.9) superionic glasses and composites at 300 K were studied. A decrease of the real part of dielectric permittivity with frequency by almost five orders of magnitude as well as one dispersion region in glasses and two dispersion regions in composites, which is reflected in the dielectric loss spectra, were observed. Frequency dependences of dielectric permittivity within the range from 10 Hz to 3x109 Hz were analyzed in the framework of the Cole-Cole model. Compositional behaviour of Cole-Cole parameters in (Ag₃AsS₃)x(As₂S₃)₁₋x (x = 0.3−0.9) superionic glasses and composites was studied. The most substantial changes were observed with the transition from (Ag₃AsS₃)₀.₄(As₂S₃)₀.₆ glass to (Ag₃AsS₃)₀.₅(As₂S₃)₀.₅ composite and from (Ag₃AsS₃)₀.₆(As₂S₃)₀.₄ composite to (Ag₃AsS₃)₀.₈(As₂S₃)₀.₂ composite

Characterization of Na1.3Al0.3Zr1.7(PO4)3 solid electrolyte ceramics by impedance spectroscopy

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On the influence of the cation vacancy on lithium conductivity of Li1 + xRxTi2 - X(PO4)3 Nasicon type materials

Structural features responsible for outstanding Li conductivity of Li1 + xRxTi2 − x(PO4)3 (LRTP) Nasicon samples (0 ≤ x ≤ 0.6 and R = Al, Sc, In) prepared by the ceramic route have been analyzed by XRD, ND, MAS-NMR and impedance spectroscopy. The structural analysis showed that all samples display the rhombohedral (S.G. R-3c) symmetry. The structural site occupancy has been investigated by 7Li, 27Al/45Sc and 31P MAS-NMR spectroscopy. The Fourier map differences deduced from high-resolution ND patterns of LAlTP samples revealed that Li ions occupy Li1 sites and to a lower extent Li3/Li3′ sites inside Li2 cavities. The location of Li at 3 sites minimizes electrostatic Li (Li1–Li3) repulsions, enhancing local mobility in LRTP samples. A maximum of conductivity was detected for 0.2 ≤ x ≤ 0.4, when a significant amount of vacant Li1 sites was created at the intersection of conduction pathways. The increment of vacant Li1 sites explains the existence of two Li motion regimes detected by 7Li NMR and impedance spectroscopy. In the low temperature regime, activation energy and migration entropy of Li have been related by the Meyer–Neldel relationship. In the high-temperature regime, further investigation is required to assess the role of vacancy in lithium conductivity.The authors thank MINECO (project MAT2010-19837-C06-02) and the regional Government of Madrid (project S-2009/PPQ 1626) for financial support. The NANOLICOM project (FP7-PEOPLE-2009-IRSES) is also acknowledged. K. Arbi wishes to thank CSIC for the contract JAE-DOC 2009