Synthesis, dielectric, conductivity and magnetic studies of LiNi1/3Co1/3Mn(1/3)−xAlxO2 (x = 0.0, 0.02, 0.04 and 0.06) for cathode materials of lithium-ion batteries

Layered structure cathode materials LiNi1/3Co1/3Mn(1/3)−xAlxO2 (x = 0.0, 0.02, 0.04 and 0.06) are prepared by the sol-gel method by adding citric acid as chelating agent. The physical, electrical and magnetic properties of the synthesized materials are systematically discussed using the structural (XRD, FESEM with EDS and FT-IR), impedance (LCR) and electron spin resonance (ESR) measurements. The X-ray diffraction pattern of the synthesized samples possessed the α-NaFeO2 structure of the space group, R3¯m, with no evidence of any impurities. The peak intensity ratio I(104)/I(003) increased with Al concentration, which indicated the cation mixing between transition metal layer and lithium layer. The field effect scanning electron microscopy showed the particle size distribution in the range of 230–250 nm and EDS has been analysed for elemental mapping. The local structure is investigated by vibrational spectroscopy in FT-IR study. The impedance studies are characterized by complex impedance spectroscopy (CIS) in the frequency range from 42 Hz to 1 MHz at room temperature (30 °C). The dielectric properties are analyzed in the framework of complex dielectric permittivity and formalism of the complex electric modulus. For these samples, the ESR analysis of magnetic measurements, the degree of cation mixing, is estimated to be Ni2+(3b) = 2.75%. Keywords: Layered structure, XRD, FESEM, FT-IR, Dielectric, ES

Structural, impedance, dielectric and modulus analysis of LiNi1-x-y-0.02Mg0.02CoxZnyO2 cathode materials for lithium-ion batteries

Mg, Co and Zn co-substituted layer-structured cathode materials LiNiCoxZnyMg0.02O2 (x = y = 0.0, 0.02 and 0.04) were prepared by a solid-state reaction method. The materials were systematically characterized by X-ray diffraction (XRD), field effect scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), and electrical impedance spectroscopy (EIS) techniques. XRD analyses revealed the formation of a rhombohedral structure in the prepared materials with a typical α-NaFeO2 layered structure within R3¯m space group. The grain size was determined by FESEM in the range from 3.19 to 3.85 μm for all materials synthesized. The site of the local cation (Li–O) and of the transition metal cations (M–O) in the materials were identified by FT-IR. The complex impedance and modulus studies suggested the presence of a non-Debye type of multiple relaxations in these materials. The dielectric constant was found to increase with increasing Co and Zn concentrations. The ac conductivity studies revealed a typical negative temperature coefficient of resistance (NTCR) behavior, and the conductivity values varied from 1.58 × 10−5 to 8.46 × 10−6 S cm−1. The activation energy determined from the Arrhenius plots at 50 Hz was in the range of 0.23–0.78 eV

Synthesis, structural and electrical studies of Ba1−xSrxCe0.65Zr0.25Pr0.1O3−δ electrolyte materials for solid oxide fuel cells

This paper is discussed Sr doping effect on the microstructure, chemical stability and conductivity of Ba1−xSrxCe0.65Zr0.25Pr0.1O3−δ (0 ≤ x ≤ 0.2) electrolyte prepared by sol–gel method. The lattice constants and unit cell volumes are found to decrease as Sr atomic percentage increased in accordance with the Vegard law, confirming the formation of solid solution with orthorhombic structure. Among them all the synthesized samples are showed a conductivity with different atmosphere values at 500 °C. Ba0.92Sr0.08Ce0.65Zr0.25Pr0.1O3−δ recorded highest conductivity with a value of 3.3 × 10−6 S/cm (dry air) & 3.41 × 10−6 S/cm (wet air with 3% relative humidity) at 500 °C due to its smaller lattice volume, larger grain size and lower activation energy that led to excessive increase in conductivity. All pellets exhibited good chemical stability when exposed to air and H2O atmospheres. This study elucidates that the composition will be a promising electrolyte material for use as SOFC at intermediate temperatures if Sr doping is limited to small amounts. Keywords: Solid oxide fuel cell, Proton conducting electrolyte, Chemical stability, Sol–gel synthesis, BaCeO

Influence of Cu-Cr substitution on structural, morphological, electrical and magnetic properties of magnesium ferrite

Cu-Cr substituted magnesium ferrite materials (Mg1 − xCuxCrxFe21 − xO4 with x = 0.0–0.7) have been synthesized by the solid state reaction method. XRD analysis revealed the prepared samples are cubic spinel with single phase face centered cubic. A significant decrease of ∼41.15 nm in particle size is noted in response to the increase in Cu-Cr substitution level. The room temperature resistivity increases gradually from 0.553 × 105 Ω cm (x = 0.0) to 0.105 × 108 Ω cm (x = 0.7). Temperature dependent DC-electrical resistivity of all the samples, exhibits semiconductor like behavior. Cu-Cr doped materials can be suitable to limit the eddy current losses. VSM result shows pure and doped magnesium ferrite particles show soft ferrimagnetic nature at room temperature. The saturation magnetization of the samples decreases initially from 34.5214 emu/g for x = 0.0 to 18.98 emu/g (x = 0.7). Saturation magnetization, remanence and coercivity are decreased with doping, which may be due to the increase in grain size. Keywords: Solid state reaction, X-ray diffraction, Crystallite size, Magnetic and electrical properties, Saturation magnetizatio

Chemically stable proton conducting doped BaCeO3 by citrate-EDTA complexing sol-gel process for solid oxide fuel cell

Proton conducting oxides Ba1-xSrxCe0.65Zr0.25Y0.1O3-δ are prepared using the citrate-EDTA complexing sol-gel method. The effect of strontium and yttrium doping on the material properties are systematically investigated using TG/DTA, XRD, SEM, EDAX, FTIR, RAMAN and LCR measurments. The results indicated a single phase orthorhombic system. Strontium incorporation helped in increasing the grain size while reducing the lattice parameters and unit cell volume. The ionic conductivities of the sintered oxides increased with increase in the concentration of Sr2+ along with the co doping strategy of trivalent Y3+ in B site. In the present work at 500 °C, exhibited high conductivity value of 2.25 × 10−3 S/cm with activation energy of 0.38 eV in wet atmosphere. These results indicate that this composition can be used as a potential electrolyte if synthesis conditions and temperature are well maintained. Keywords: Solid oxide fuel cell, Proton conducting electrolyte, Chemical stability sol-gel synthesis, Ba1-xSrxCe0.65Zr0.25Y0.1O3-δ, Perovskit

Structural, morphological, impedance and magnetic studies of nanostructured LiNi0.45M0.1Mn0.45O2 (MCu and Al) cathode materials for lithium-ion batteries

Layered structure LiNi0.45M0.1Mn0.45O2 (MCu and Al) cathode materials for lithium-ion batteries are synthesized by solâgel auto combustion method. The structural, morphological, electrical and magnetic properties are examined by X-ray diffraction (XRD), field effect scanning electron microscope FESEM, FT-IR, EIS and ESR. XRD data revealed the rhombohedral and α-NaFeO2 structure with a space group R-3m. The electrical conductivity, dielectric constant, and dielectric loss are measured in the room temperature at a frequency ranging from 20 Hz to 1 MHz. The electrical conductivity of the compound is measured by AC impedance. An effective improvement in the electrical conductivity of order 5.42 Ã 10â6 S/cm is observed for the copper doped LNMO compounds. ESR spectra is recorded at room temperature on a Bruker EMX model X-band spectrometer operating at a frequency of 9.50 GHz. The critical dopants of Cu, with minimum g-factor and maximum line-width (W) are observed. Keywords: Solâgel, FESEM, AC impedance, ES