Citric Gel Method Research Articles

Magnetization sign reversal, exchange bias, and Griffiths-like phase in orthorhombic perovskite Pr2FeMnO6

Abstract The perovskite Pr2FeMnO6 has been synthesized by citrate-gel combustion method. The material has an orthorhombic crystal structure with Pbnm space group. The presence of Fe3+ and Mn3+ cations in the material are confirmed by XPS analysis. A magnetization sign reversal is observed for the material at low-temperatures in low applied magnetic fields. When the applied field or temperature is increased, the negative magnetization got diminished. Such a sign reversal of magnetization is observed for the material as a result of the interaction between components of paramagnetic Pr3+ and Mn3+ moments opposite to the component of the ferromagnetic Fe3+ moment or the anti-aligned Fe-rich regions to that of Mn-rich regions containing with Pr3+. Negative exchange bias is also exhibited by Pr2FeMnO6 below 200 K which can be ascribed to the Dzyaloshinskii-Moriya interaction and magnetic exchange anisotropy. A high-temperature magnetic transition at TC = 576 K is identified for the material from the thermomagnetic data. From the detailed analysis of the thermomagnetic data, the presence of ferromagnetic short-range correlations is observed far above the TC, which suggests a Griffiths-like phase with Griffiths temperature at TG = 681 K.

Temperature-dependent phase transition: Structural and magnetic properties of Ba0.5Sr0.5Fe12O19-CoFe2O4 nanocomposites

Ba0.5Sr0.5Fe12O19(hard)-CoFe2O4(soft) nanocomposite ferrites synthesized using the citrate-gel combustion method was subjected to different annealing temperatures (Ta) (700 °C, 800 °C, 900 °C, and 1000 °C), and the resultant structural and magnetic properties were investigated. The microstructural characterization of nanocomposites via X-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM) analysis at first revealed the dominance of soft phases annealed at 700 °C and then showed the presence of hard phases at 900 °C. Lattice vibrational analysis again showed a clear distinction between the bands corresponding to Ta at 700 °C and 900 °C. An increase in saturation magnetization (MS) and coercivity (HC) was observed upon increasing the Ta. A good combination of MS (56.9 emu/g) and HC (3.3 kOe) was obtained at Ta = 900 °C. In addition, high-temperature magnetic studies confirmed the dominance of soft phase with Curie temperatures of 592 °C and 480 °C for the samples annealed at 700 °C and 900 °C, respectively. Combining these facts, a detailed mechanism involving the domination of spinel plates and hexagonal layers was drawn. The magneto crystalline anisotropy was evaluated and showed a maximum for Ta at 900 °C. The extent of exchange coupling between the hard and soft phases was further analyzed by switching field distribution curves and is discussed in detail.

Structural and Optical Studies on Nanosized Thermoelectric Oxide-Zn1−xAlxO

Aluminum doped ZnO ([Formula: see text]AlxO, [Formula: see text], 0.02, 0.03 and 0.04) (AZO) nanoparticles were synthesized using citrate-gel method. We report the effect of aluminum doping along with variation of metal to citrate ratio on structural and optical properties of AZO nanoparticles with crystallite size optimization. The X-ray diffraction analysis confirmed Wurtzite crystal structure wherein the crystallite size was within the range of 15–40[Formula: see text]nm. Optical properties were studied with the help of UV-Visible spectroscopy. Bandgap calculated using Tauc plot is found to be between the range of 2.39–2.75[Formula: see text]eV and morphological analysis using Scanning Electron Microscopy (SEM) showed the distribution of synthesized material.

Effect of La2O3 Dopant on Microstructure and Electrical Nonlinearity of ZnO-CaMnO3 Based Varistor Ceramics

In this research, zinc oxide based varistor are produce by using citrate-gel method compared to conventional solid-state method. The zinc oxide based varistor are fabricate using three different wt.% of ZnO-CaMnO3-La2O3 and divided into three system which are 80 mol% ZnO + 20 mol% CaMnO3, 79.5 mol% ZnO + 20 mol% CaMnO3 + 0.5 mol% La2O3 and 78.5 mol% ZnO + 20 mol% CaMnO3 + 1.5 mol% La2O3. ZnO-CaMnO3-La2O3 compound experienced pre-sintering at 500 °C for 2 hours sintering time. In the sintering condition, sintering temperatures are manipulated, which are varied at 1100, 1200 and 1300 °C while, the sintering time is setting at 4.5 hours. X-ray diffraction patterns show this compound is high in crystallinity. The surface morphology with the average grains size between 2.0 ∼ 10.0 μm was observed by Scanning Electron Microscopy. Energy Dispersive Spectroscopy confirmed that distribution of element are homogenous with high purity. Density of the sample product is range between 5.0 ∼ 5.6 g cm−3. J-E characteristic shows the value of non-linearity coefficient in the range of 1.10 to 4.35.

The Study on the Reaction Order and Kinetics of Total Oxidation Reaction of m-xylene over LaMnO3 Perovskite Catalyst

Gases of m-xylene is one of the popurlar toxic pollutants in the exhaust gases, it is emitted into the environment from factories and engines because the fuel in the engine does not burn completely. The best solution in order to remove this toxic gases of m-xylene to protect the environment is transforming them completely into CO2 and H2O by catalysts. Perovskite of LaMnO3 is one of the catalysts that was synthesized and studied the catalytic properties in total oxidation of m-xylene in our previous report. Obtained results showed that the LaMnO3 perovskite has good catalytic characterizations such as large surface area and the amount of α-oxygen adsorbed on the catalyst is large too. So, it exhibits a good catalytic activity in total oxidation of m-xylene at relatively low reaction temperature. In present work, the reaction order and kinetics of this reaction are determined. The obtained results demonstrated that the reaction order value with respect to m-xylene is equal to about 1, to oxygene is proximately equal to 0 and the order of reaction is equal to about 1. Based on reaction order data, it was thought that the pathway of m-xylene oxidation by air oxygen over LaMnO3 may be followed through which the Langmuir - Hinshelwood mechanism.
 Keywords
 Catalyst, perovskite, oxidation, m-xylene, kinetics
 References
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Spark plasma sintering of ZrB2 powders synthesized by citrate gel method

The densification behavior of nanocrystalline zirconium diboride (ZrB2) powders with nickel (5 vol%) is reported by spark plasma sintering (SPS) technique. SPS experiments were performed at 1600 and 1900 °C with 65 MPa pressure and 1 min holding time. A maximum relative density around 95% was obtained after SPS processing of ZrB2 at 1900 °C while the density of ZrB2 sample sintered at 1600 °C reached 88% of the theoretical density. Hardness and fracture toughness values are 11 GPa and 4.11 MPa m1/2 for the sample sintered at 1600 °C and 13.7 GPa and 2.65 MPa m1/2 for the sample sintered at 1900 °C, respectively.

Preparation of neat and capped BaFe2O4 nanoparticles and investigation of morphology, magnetic, and polarization effects on its microwave and optical performance

In this study, pure BaFe2O4 nanoparticles were prepared using the citrate gel method and then the presence of glucose as a novel organic capping agent on its characteristics was explored. Moreover, neat BaFe2O4 nanostructures were synthesized at 650 °C or 850 °C, which results confirmed the heat treatments have a significant effect on its properties. Besides, microwave absorbing mediums were compared by silicone rubber or Polyvinylidene fluoride (PVDF) polymeric matrices. The Fourier transform infrared (FT-IR) revealed that BaFe2O4 structures at 650 °C or 850 °C, as well as capped nanoparticles at 850 °C were formed without any organic impurities. The results of the vibrating sample magnetometer (VSM) exhibited that the heat treatment at 850 °C led to an increase in the saturation magnetization (Ms) as well as on one hand organic capping agent diminished Ms, on the other hand, enhanced the isotropic magnetic property of the nanoparticles. X-ray powder diffraction (XRD) patterns illustrated pure crystal structure for all three samples with a size of 10.2 nm calculated by the Scherrer equation. Additionally, field emission scanning electron microscopy (FE-SEM) and diffuse reflection spectroscopy (DRS) analysis illustrated that the calcination temperature and organic capping agent respectively changed morphology and band gap of synthesized nanostructures. Finally, Microwave absorption properties were studied using vector network analyzer (VNA). Based on the results, the maximum reflection loss of capped BaFe2O4 at 850 °C/silicone rubber nanocomposite was −82.74 dB at 11.2 GHz with a thickness of 2.5 mm also BaFe2O4 at 650 °C/silicone rubber nanocomposite absorbed 7.39 GHz bandwidth more than 10 dB with a thickness of 2 mm in the x and ku-band frequency.

Synthesis of Co1–xZnxFe2O4 and Evaluation of Structural, Magnetic, Antimicrobial Properties of ZnFe2O4, Co0.6Zn0.4Fe2O4 by Citrate Gel Method, Calcined at 600°C

Co1–xZnxFe2O4 was prepared by citrate precursor method using raw materials: citric acid, cobalt, zinc and iron nitrates and by following calcination at 600°C. This assessment presents the effect of substitution of the Zn2+ ion on the structural properties of cobalt nanoferrite. The structural characteristics of the calcined samples were determined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). X-ray diffraction studies of the nanoparticles heat-treated at 600°C confirms that the crystallite size is in the range of 22 to 29 mm and also the X-ray diffraction analysis indicates the formation of single phase ferrite particles in nano size. The morphology of the calcined sample was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mean particle size of Co0.6Zn0.4Fe2O4 was determined to be 19 nm calculated from TEM which is supporting the X-ray diffraction studies. The Fourier transform infrared spectra (FTIR) show two strong absorption bands in the series of ferrites between the range of 4500–500 cm−1 responsible for the characteristic of spinel ferrites. The high-frequency band and low-frequency band are assigned to the tetrahedral and octahedral complexes, respectively. The weight %, atomic %, and elemental analysis of calcined samples were confirmed by elemental spectral signals of energy dispersive spectroscopy (EDS). At the room temperature, magnetic measurements of pure ZnFe2O4 and Co0.6Zn0.4Fe2O4 were calculated based on hysteresis curves (Hc), it is observed that the substitution of nonmagnetic Zn2+ ion increases the magnetic behavior in mixed cobalt-zinc ferrites. The antimicrobial activity of ZnFe2O4, Co0.6Zn0.4Fe2O4 synthesized nanoferrites has been successfully tested against harmful microbes.

Charge transfer mechanisms in strontium ferromolybdate with tunneling barriers

The single-phase strontium ferromolybdate powder with the double perovskite structure has been synthesized by the citrate-gel method with superstructural ordering of iron and molybdenum cations of 88%. The formation of the SrMoO4 phase on the intergrain boundaries has been determined by means of the XRD studies, the Electrokinetic Sonic Analysis technique, and FESEM investigations of pressed Sr2FeMoO6-δ powders subjected to the isothermic treatment at 700 K and p(O2) = 10 Pa. The temperature dependence of the electrical resistivity in the temperature range 4.2–300 K has a metallic type in the single-phase Sr2FeMoO6-δ compound and the semiconductor type in the Sr2FeMoO6-δ–SrMoO4–Sr2FeMoO6-δ structure with dielectric sheaths. In the latter case, a hopping mechanism of charge transfer is observed. In the applied magnetic field, the temperature dependence does not change qualitatively; however, the resistivity decreases with increasing field, i.e., a negative magnetoresistive effect appears, reaching 43.6% at 10 T and 10 K. The external field forms a collinear spin structure, thus increasing the spin-polarized current through the energy barriers in the granular Sr2FeMoO6-δ–SrMoO4–Sr2FeMoO6-δ heterostructure.

Tuning the dimensionality of layered Srn+1Tin−xNixO3n+1 perovskite structures for improved activity in syngas generation

Interest in perovskite type oxides is growing due to their versatile catalytic applications. A series of Ruddlesden-Popper (RP) type layered perovskite oxides Srn+1Tin−xNixO3n+1 were prepared and evaluated for their catalytic activity in steam reforming, CO2 reforming and bi-reforming of methane. These materials, prepared through citrate gel method were characterized to understand their structure and Ni reducibility. Substitution of Ni in RP phases was established through refinement of XRD powder pattern. During methane reforming, the catalytic activity increased with the order of RP phase of SrTi1−xNixO3−δ (n = ∞). TPR results show variation in Ni reducibility with the order of RP phase, while TPD-O2 study helped to estimate oxygen vacancies. These vacancies seem to influence catalytic activity during methane reforming. Transient pulse experiments show that CO2 dissociates over oxygen vacancies to give CO and oxygen, with later replenishing lattice oxygen in SrTi0.8Ni0.2O3−δ (n = ∞) phases. Highly labile oxygen vacancies generated in the bulk of SrTi0.8Ni0.2O3−δ must be migrating to the surface, helping in the removal of coke formed. Characterization of catalysts after reaction helped in better understanding of coke precursors.

Influence of morphology on luminescence properties of xenotime-type phosphors NaYP2O7:Eu3+ synthesized via solid state and citrate-gel routes

A series of Eu3+ activated xenotime type rare earth phosphate NaYP2O7 based orange–red emitting phosphors have been prepared via solid state (SS) and citrate gel (CG) methods. The morphological variation of the developed phosphors concerning synthesis method and heat treatment has significantly influenced the luminescence properties. The phosphors synthesized by the CG route reveals the formation of homogeneous powder with small particles along with uniform size. The developed phosphors exhibit intense orange–red emission under 394 nm near UV excitation with a full width half maximum ~ 2 nm. Compared with the phosphors synthesized by SS route, the phosphors obtained by CG method possess enhanced and sharper orange–red emission with longer lifetimes due to the 5D0–7F1–2 transitions. The developed narrow red emitting phosphors have better emission intensity in comparison with commercially available Y2O3:Eu3+ red phosphors. Thus, these phosphors could be a suitable candidate for solid state lighting applications for the fabrication of white light emitting diodes.

The Impact of Ni Substitution on the Structural and Magnetic Properties of Mg Nano-Ferrite

Magnesium substituted nickel nano-ferrite Mg1−xNixFe2O4 (x = 0.0, 0.1, 0.3, 0.5, 0.7, and 1.0) was synthesized by the citrate-gel auto-combustion method. Synthesized powders were sintered at 600 ∘C for 4 hours and characterized by X-ray, High Transmission Electron Microscopy, Brunauer-Emmett-Teller, Atomic Force Microscopy and Energy Dispersive X-ray Spectroscopy analyses. The impact of replacing Mg ions by Ni on the structural parameters and magnetic properties of the system was investigated utilizing X-ray diffraction and χ–T magnetic measurements at room and low temperatures. The crystallite sizes were found in the range of 24.6 nm – 27.6 nm. The variation of lattice parameter, the roughness, surface area and the porosity size upon increasing the Ni content were determined and then correlated with the cation distribution and the magnetic behavior. The coercivity (Hc) values vary from 56.4 Oe to 130 Oe. These values make the investigated samples well suited for their use in recording media. Magnetic parameters such as saturation magnetization, and Curie temperature (Tc) assured the existence of a critical concentration at x = 0.3 in which the anomalous character appeared.

Elastic properties and antistructural modeling for Nickel-Zinc ferrite-aluminates

In this study, elastic properties of nanocrystalline Ni-Zn-Al ferrite synthesized by citrate-gel autocombustion method has been presented. X-ray diffraction and Infrared spectroscopy confirms the formation of spinel phase. Elastic properties are estimated from force constants and lattice constant determined from FTIR and XRD respectively. The observed variation of elastic constants has been interpreted in terms of strength of interatomic bonding and electronic configuration of the cations involved in the system. The average grain size has been observed to decrease with Al3+ substitution. A new antistructural modeling for describing of active surface centers is discussed. With this new antistructural modeling the changes in concentration of donor's active centers Ni′B and acceptor's active centers FeA• and AlA• was explained.

Study of structural, dielectric and magnetic properties of Li0.5+0.5xFe2.5–1.5xPbxO4 ferrite nano-crystals synthesized by citrate gel method

The effect of Pb substitution on the structure, dielectric, impedance and magnetic properties of Li0.5+0.5xFe2.5–1.5xPbxO4 ferrite nano-crystals prepared by citrate gel method has been investigated. X-ray diffraction analysis confirmed the formation of cubic spinel phase and broadness of reflection peaks indicates the formation of smaller sized crystallites. The average crystallite size was observed to increase from 21.3 to 26.1 nm on increasing Pb substitution in Li0.5+0.5xFe2.5–1.5xPbxO4 ferrite. The surface analysis of the samples was performed using scanning electron microscopy. An improvement in the microstructure has been obtained on Pb doping. Dielectric and impedance measurements were carried out in the frequency range of 100 Hz–10 MHz. The dielectric properties of Li0.5+0.5xFe2.5–1.5xPbxO4 ferrite samples were improved much by the substitution of Pb ions. The low dielectric loss at higher frequencies identifies the potential of these ferrites for high frequency applications. Interestingly, a very large value for dielectric constant of the order of 107 has been obtained on Pb doping. The impedance spectroscopy technique was used to study the effect of grain and grain boundary on the electrical properties of the material. From the present investigation on Li0.5+0.5xFe2.5–1.5xPbxO4 ferrite, one can conclude that the substitution of Pb4+ ions play an important role to modify the magnetic and electrical properties of lithium ferrite desired for microwave devices and power applications.

Active and durable alkaline earth metal substituted perovskite catalysts for dry reforming of methane

Dry reforming of methane is an important process for the utilization of CO2 and to get valuable synthesis gas. Alkaline earth metal substituted MZr1-xNixO3-δ perovskites were synthesized by citrate gel method, characterized and evaluated for dry reforming methane. Characterization results show that the type of alkaline earth substituted at the A site of the perovskite oxide plays an important role in terms of structure, basicity, oxygen deficiency and Ni dispersion. Calcium substituted CaZr0.8Ni0.2O3-δ catalyst shows superior activity in terms of high CH4 and CO2 conversion, while maintaining the activity even after 500h of reaction. Mechanistic investigations were carried out using transient pulse experiments and insitu FTIR-diffuse reflectance spectroscopy. These experiments reveal that redox property and basicity play important role in activation and sustaining the reforming reaction. Insitu FTIR measurements show that surface hydroxyl groups of the support are vital for high activity and durability of CaZr0.8Ni0.2O3-δ catalyst. XRD and TGA analysis of catalysts after reaction show the structures are retained, but peaks pertaining to coke were observed on SrZr0.8Ni0.2O3-δ and BaZr0.8Ni0.2O3-δ catalysts. On the otherhand, CaZr0.8Ni0.2O3-δ catalyst had only amorphous carbon even after 500h of reaction. HRTEM studies revealed that SrZr0.8Ni0.2O3-δ and BaZr0.8Ni0.2O3-δ catalysts deactivated mostly due to the formation of carbon nanotubes with Ni embedded in them. Raman and XPS analysis helped in identifying types of coke precursors present on the catalysts. The investigation also illustrate that type of carbon formed depends on the basicity of perovskite oxide, metal to support interaction, Ni crystallite size, surface hydroxyl groups and oxygen defects. This study clearly demonstrated that CaZr0.8Ni0.2O3-δ is an excellent catalyst for dry reforming reaction with long life.

Influence of rare earth ion doping (Ce and Dy) on electrical and magnetic properties of cobalt ferrites

Ce and Dy substituted Cobalt ferrites with the chemical composition CoCexDyxFe2-2xO4 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were synthesized through the chemical route, citrate-gel auto-combustion method. The structural characterization was carried out with the help of XRD Rieveld analysis, SEM and EDAX analysis. Formation of spinel cubic structure of the ferrites was confirmed by XRD analysis. SEM and EDAX results show that the particles are homogeneous with slight agglomeration without any impurity pickup. The effect of RE ion doping (Ce and Dy) on the dielectric, magnetic and impedance studies was systematically investigated by LCR meter, Vibrating Sample Magnetometer and Impedance analyzer respectively at room temperature in the frequency range of 10 Hz–10 MHz. Various dielectric parameters viz., dielectric constant, dielectric loss and ac conductivity were measured. The dielectric constant of all the ferrite compositions shows normal dielectric dispersion of ferrites with frequency. Impedance analysis confirms that the conduction in present ferrites is majorly due to the grain boundary mechanism. Ferrite sample with x = 0.03 show high dielectric constant, low dielectric loss and hence can be utilized in high frequency electromagnetic devices. Magnetization measurements indicate that with increase in Ce and Dy content in cobalt ferrites, the magnetization values decreased and coercivity has increased.

Structural and magnetic properties of multiferroic Y2NiMnO6 double perovskite

ABSTRACTThe double perovskite Y2NiMnO6 is prepared by a citrate-gel combustion method. The structural, magnetic and dc transport properties of Y2NiMnO6 are investigated systematically. A monoclinic crystal structure having space group P21/n is identified for the material from XRD. Magnetic structure is characterized by isothermal and thermomagnetic studies. The material possesses a ferromagnetic transition at 88 K. The dynamic magnetic structure of the material is analyzed using the ac susceptibility data. Resistivity data suggests the semiconducting behavior of the material. The work provides well advancement in researchers on potential material for spintronic applications.

A perovskite-structured aluminium-substituted lithium lanthanum titanate as a potential artificial solid-electrolyte interface for aqueous rechargeable lithium-metal-based batteries

An aluminium-doped lithium lanthanum titanate (A-LLTO) solid electrolyte was prepared using a simple citrate-gel method, and this was followed by a pelletization and the conventional sintering process. When the sintering time was varied at 1350°C for the synthesis of the A-LLTO, the A-LLTO ceramic that was sintered at 1350°C for 6h exhibited the highest ionic conductivity of 3.17×10−4Scm−1 at 25°C. In addition, the stability and durability of the synthesized A-LLTO ceramic was tested through a one-month aqueous-solution immersion for which the pH values were varied between 0 and 14. The stability of the A-LLTO is the highest in the alkaline environment; furthermore, for its use in the aqueous-electrolyte environment, a protected lithium electrode (PLE) structure was made by combining the lithium (Li) metal, a lithium phosphorous oxynitride (LiPON) interlayer, and the A-LLTO, whereby the LiPON interlayer prevented a direct reaction between the Li metal and the A-LLTO. The Li-LiCoO2 and Li-O2 cells comprising the PLE exhibited a superior electrochemical performance when they were used in the alkaline 1M LiNO3-electrolyte environment. After 100 cycles of the charge-discharge at the 1C rate, the aqueous Li-LiCoO2 cells maintained 59.3% of the initial capacity with a coulombic efficiency of 98.3%. In addition, the aqueous Li-O2 cell operated stably for 40 cycles under the limited capacity mode of 0.5mAhcm−2. The outstanding performance of the Li-metal-based cells originates from the A-LLTO solid electrolyte, due to the latter’s high stability, ionic conductivity, and an effective suppression effect regarding the dendritic growth of the Li.

Influence of preparation method on activity and stability of Ni catalysts supported on Gd doped ceria in dry reforming of methane

Nickel catalysts supported on Gd doped ceria (NGDC), with various Ni content, were prepared through different preparation routes and evaluated for dry reforming of methane (DRM). Their detailed characterization revealed that method of preparation plays an important role in Ni dispersion, with catalysts prepared through co-precipitation showing high Ni dispersion. The co-precipitated 12NGDC-cp catalyst with 12wt% NiO was found to be superior in terms of high CO2 and CH4 conversions compared to catalysts prepared through citrate gel or impregnation methods Even H2 and CO yields are high on this catalyst, while it shows excellent durability with stable activity even after 100h on-stream. Thermogravimetric analysis of spent catalyst showed presence of coke, with transmission electron microscopic studies pointing to the presence of Ni crystallites at the mouth of the carbon whiskers. These Ni crystallites appear to be still active for DRM reaction. Among the spent catalysts, the carbon formation was high on catalysts that have bigger Ni crystallites, with the catalysts prepared through impregnation and citrate gel methods having higher coke. Investigations also reveal that the conversion of active (amorphous) carbon into stable (graphitic) carbon depends on the Ni crystallite size, temperature and duration of the reaction. These studies demonstrate that Gd doped ceria is a good support for Ni, to obtain high DRM activity and very good on-stream stability provided the catalysts are prepared through an appropriate method.

High Performance All-Solid State Lithium-Air Batteries Employing Aluminum-Substituted Lithium Lanthanum Titanate Solid Electrolyte

Recently, lithium(Li)-air battery has attracted much attention due to its extremely high theoretical specific energy density as 11,680 Wh kg-1 Li, which can be even comparable to that of gasoline. Despite potential of Li-air battery, the commercialization of the battery is a great challenge, since it can suffer from plenty of problems majorly associated with the use of liquid electrolytes and metallic Li anode; leakage, flammability, electrochemical instability under reduced oxygen environment and uncontrollable dendritic growth of Li. In this study, to address these issues, all-solid state Li-air battery has been proposed. By using a stable solid electrolyte with proper Li+ conductivity, the risks of leakage, short-circuit and fire/explosion can be successfully addressed. Moreover, the solid electrolyte can act as a barrier to protect Li metal from harmful gases such as O2, CO2 and moisture diffusing from outside air. In this study, we used aluminum-substituted lithium lanthanum titanate (A-LLTO) ceramic as a main ceramic solid electrolyte for all-solid state Li-air batteries. Herein, A-LLTO ceramic with a nominal formula of (Li0.33La0.56)1.005Ti0.99Al0.01O3 was prepared using citrate-gel method. In particular, the air electrode was specially designed by engaging a thin layer solid electrolyte to form an integrated cathode structure. The integrated cathode consisted of a dense ~20-µm-thick A-LLTO solid electrolyte layer adhering to the 500-µm-thick pellet of porous cathode. Moreover, CoO catalyst particles were directly deposited on the surface of A-LLTO cathode backbone. Further, due to instability of A-LLTO solid electrolyte against Li metal anode, an interlayer of composite gel polymer electrolyte (CGPE) was inserted between A-LLTO and Li metal. The interlayer CGPE was stabilized by the addition of small amount of an ionic liquid. After cell assembly, the solid-state Li-air cell was cycled at the current density of 0.3 mA cm-2 in pure O2 gas atmosphere at 50 oC. Under the limited capacity mode of 500 mAh g-1, the cell exhibited the cycle life of 132 cycles. During the cycling process, the discharge potential of the cell almost remained. Meanwhile, the charge cell potential appeared to increase significantly. By using SEM, XPS and Raman spectra analysis, the formation of reaction products on the cathode surface after cycling test was identified. With the increase in cycle number of discharge-charge, the amount of reaction products was found to increase. This demonstrates the degradation of catalytic activity of CoO catalyst. Because Li2O2 possesses the low Li ionic conductivity of 4×10-19 S cm-1 and low electrical conductivity of 5×10-20 S cm-1, it hinders the transportation of electrons and Li+ ions in the cathode. Accordingly, the degree of polarization for the cell increased gradually with cycle. Although the solid state Li-air cell developed in this work could prevent the problems which can happen when liquid electrolyte is used, its life span was not still satisfactory. Therefore, the factors such as operation temperature, catalyst type, which can enhance the kinetics for the reaction process, needs to be investigated further.