Increase In Average Crystallite Size Research Articles

Crystallinity tuning of LCNO/graphene nanocomposite cathode for high-performance lithium-ion batteries

In this work, a graphene-enhanced LiCo0.525Ni0.475O2 (LCNOG) cathode was synthesized by self-propagating high-temperature synthesis and the effects of annealing at 650–850 °C were investigated. Sharper X-ray diffraction peaks showed enhanced crystallization with an increase in average crystallite size from 28 nm to 56 nm after annealing at 850 °C. LCNOG annealed at 850 °C delivered a high capacity of over 2030 J compared to 1280 J, with a near ideal coulombic efficiency of 99.5 % and long cycle stability. The acceleration of kinetics is evidenced by more favorable redox peak positions in voltammetry and a 5-fold lower interfacial resistance in electrochemical impedance spectroscopy. The improved performance is due to the larger grain size, higher crystallinity, increased conductivity and graphene-induced diffusion facilitation. The relationship between crystallinity and cathodic properties provides critical insight into cathode design. The exceptional performance achieved by tailoring crystallinity through annealing makes LCNOG a potential material for high-voltage cathodes for lithium-ion technology.

Ag nanoparticle assisted vertically aligned β-Ga2O3 nanowire deposited by GLAD technique for ultrafast photodetection

In this study, we report the fabrication of Silver (Ag) nanoparticle (NP) assisted vertically oriented β-Ga2O3 nanowires on Silicon (Si) - substrate by the Glancing angle deposition (GLAD) technique. The fabricated samples were annealed at 900 °C. The optoelectronic properties of both As-deposited and annealed devices are studied thoroughly. The sample shows an increase in average crystallite size upon annealing with a decrease in lattice strain and dislocation density. FEG-SEM image confirms the growth of well-aligned vertically oriented nanowires with Ag NP in the midway of each nanowire. The UV–Vis absorption spectra show that Ag NP's presence results in the appearance of a significant absorption hump in the visible range, thereby broadening the light absorption capability of β-Ga2O3. The improvement in crystalline quality and reduction in defects after annealing resulted in a better response for the annealed device. These results indicate that annealing the Ag NP-assisted β-Ga2O3 NW device could become a feasible option for high-speed photodetectors, as it demonstrates a faster photoresponse time and a lower turn-on voltage.

Structural, morphological, optical, and thermal properties of electrospun PbS/PVP-PEO nanofibers

This study describes the preparation and characterization of PVP-PEO nanofibers filled with PbS nanoparticles. The effect of polymer concentrations, surface morphology, and diameter distribution studies of the nanofibers was evaluated by Scanning Electron Microscopy (SEM). The SEM images revealed that smooth and homogeneous nanofibers could be achieved at 12% PVP-PEO (50:50 wt%) concentration. The XRD and TEM analysis confirmed the formation of PbS nanoparticles in the PVP-PEO blend matrix, which also revealed the high crystalline behaviour of the PbS nanoparticles. The XRD data showed that the intensity and average crystallite size increase with PbS concentration. The FTIR and TGA studies revealed the interaction between PbS nanoparticles and the PVP-PEO blend matrix. UV–Vis diffuse reflectance studies have shown that the reflectance onset shifted toward a blue shift than bulk PbS. The optical bandgap determined using the Kubelka-Munk function lies 1.08–1.56 eV range by varying PbS concentration.

Efficacy of surface-functionalized Mg1-x Co x Fe2O4 (0 ≤ x ≤ 1; Δx = 0.1) for hyperthermia and in vivo MR imaging as a contrast agent.

Surface-functionalized Mg1−xCoxFe2O4 (0 ≤ x ≤ 1; Δx = 0.1) can be an exciting candidate as an MRI contrast agent and for thermotherapeutic applications. The figure-of-merit, T2, relaxivity, r2, of MRI and specific loss power, SLP, of hyperthermia depend on the structural and magnetic properties of the nanoparticles. We synthesized cobalt-substituted magnesium ferrite Mg1−xCoxFe2O4 (0 ≤ x ≤ 1 with Δx = 0.1) nanoparticles using a chemical co-precipitation method. The lattice parameter and average crystallite size increase with the increase in cobalt content. The force-constant of FTIR of the tetrahedral sites increases, and that of the octahedral sites decreases with an increase in cobalt content. The room temperature Mössbauer spectra of Mg1−xCoxFe2O4 show that the Mössbauer absorption area of the A site decreases, and the Mössbauer absorption area of the B site increases with x. The Mössbauer spectra and M–H hysteresis loops at room temperature confirmed that a transition from fast relaxation (superparamagnetic) to mixed slow/fast (superparamagnetic/ferrimagnetic) relaxation occurs with changing cobalt content. The cobalt ion tends to occupy the octahedral B site, which makes the A–B interaction stronger; therefore, we see the above transition. Cytotoxicity experiments on HeLa cells revealed that both chitosan and chitosan-coated magnesium cobalt ferrite nanoparticles are biocompatible. In the Mg1−xCoxFe2O4 series, both r2 and SLP increase with x because of the increase in magnetization and anisotropy.

Pulsed plasma surface modified omeprazole microparticles for delayed release application

In the present work, pulsed radio frequency (RF) plasma (PRFP) was used to functionalize omeprazole (OME) microparticles using precursor monomers methacrylic acid (MAA) and methyl methacrylate (MMA). This method had two significant factors involved – 1) ratio of monomer flow rate and 2) graded deposition by systematically varying the duty cycle of pulsed plasma. The MAA flow was set to 100 cc/min and MMA to 200 cc/min to rationalize the ratio (1:2) of monomers. Systematic variation in duty cycle (keeping ON time constant and increasing OFF time of the pulse) ensured graded deposition and functionalization of OME. The plasma functionalized OME microparticles were evaluated in-vitro via dissolution studies in pH 1.2 buffer showed a cumulative release of 3.6–9.1% within 120 min compared to complete release under 60 min in pH 6.8. Raman analysis exhibited the absence of peaks from 1800 to 1000 cm−1 and XPS studies showed an increase in oxygen-containing moieties on plasma functionalized OME surface. Thermal, NMR and HR-MS analysis confirmed successful deposition without alteration in original OME molecular structure. The decreased contact angle of post plasma treated OME resulted from hydrophilization of the OME surface. XRD data of plasma treated OME showed an improved degree of crystallinity with an increase in average crystallite size. Post plasma treated OME microparticles size through DLS corroborated well with SEM. Thus, the use of graded PRFP functionalization has proved it's potent to deliver a new, safe, and cheaper alternative to contemporary drug surface modification methods.

Synthesis and Study of Calcination Effect of Zinc Ferrite on the Structure and Morphology of Nanoparticles

Three samples of spinel powdered zinc ferrites were successfully fabricated via microwave-assisted combustion method followed by calcination at temperature of 500oC for three hours. Phase purity and surface morphology that estimated via XRD pattern and field emission-scanning electron microscopy images (FE-SEM) showed that the samples have cubic spinel - structure with average crystallite size is increase from 15.8 nm to 26.53 nm and from (23.03nm to 28.16 nm when glycine–to-nitrate ratio is decreased before and after calcination at 500 oC for three hours. However the calcination results is increase in average crystallite size and average lattice constant. FE-SEM image indicated that the particles Zinc ferrite possesses shape symmetry and uniformity. Fourier transform infrared spectroscopy (FT-IR) were us to study vibration mode in synthesized spinel ferrite. As calcination the absorption band of a specific bonds are shifted to a lower wavenumber.

Influence of substrate temperature on delafossite CuFeO2 films synthesized by reactive magnetron sputtering

Delafossite CuFeO2 films have been synthesized by reactive magnetron sputtering at different substrate temperatures from 380 up to 550 °C. The films adopt the rhombohedral structure from 380 to 550 °C. At the highest temperature, the delafossite phase partially dissociates in FCC Cu and Fe3O4 magnetite phases. In addition to the average crystallite size increase, a change of the preferential orientation in the out-of-plane direction from the [012] to [006] directions occurs between 460 and 510 °C. Modelling of the optical properties shows the presence of 2 interband transitions in the visible range. The 1st main transition at 1.5 eV is ascribed to the absorption component parallel to the c-axis whereas the 2nd transition (2.10 – 2.26 eV) is related to the absorption component in the (a, b) plane. Both evolutions with temperature of the refractive index (~ 2.5) and absorption coefficient (~ 10-3 cm-1) in the infrared suggest the formation of secondary phases. The electronic conductivity, dominated by positive charge carrier, varied from 0.01 to 10 S m-1 according to the preferential orientation and to the presence of secondary phases. A very small amount of a short-range ferromagnetic component (magnetization ~ 10 kA m-1 at 1.5 T) is clearly observed at room temperature thanks to magnetometry confirming the formation of secondary phases undetected by X-ray diffraction. In addition to depend on the film orientation, the presence of secondary phases in weak proportion alters the optical and electrical behaviours such as the transmittance in the visible range.

Effect of Mn-adding on microstructure, optical and dielectric properties Zn0.95Al0.05O nanoparticles

Pure ZnO and Zn0.95-xAl0.05MnxO (x = 0, 1, 3, 5) nanoparticles (NPs) were successfully produced through co-precipitation method. The doped ZnO nanoparticles were characterized by using X-ray diffraction (XRD), Williamson-Hall plot (W–H Plot) and field emission electron microscope (FESEM) analysis. The XRD patterns revealed that all samples exhibit crystalline hexagonal (wurtzite) structure of the ZnO NPs. The change in lattice parameters (a, c), preferential crystalline orientation for Mn doped samples, change in bond length and micro-strain after doping indicate successful incorporation of Mn2+ in Al-doped ZnO NPs. Further, the increase in average crystallite size directed the improvement in the crystalline nature. FESEM was used to study the morphological analysis of pure and doped ZnO NPs. UV Vis spectroscopy results indicate that the optical transmission improved in the visible region and band gap decreases as a result of doping. The improvement in the dielectric loss due to Mn content doping was observed and is associated with increase in the number of defects. The decrease in ac conductivity (σac) with Mn content is related with increase amount of defects.

Investigation of Impact of Biofield Energy Healing Treatment on Physicochemical, Thermal and Spectral Properties of Magnesium Gluconate

Magnesium plays important role in the functioning of cells, nerves, muscles, and bones of human body. It is incorporated in the form of magnesium gluconate in various pharmaceutical and nutraceutical supplements due to its wide applications. This study was done with the objective to analyse the effect of The Trivedi Effect®- Energy of Consciousness Healing Treatment on the physical, thermal, and spectral properties of magnesium gluconate. In this regard, the sample of magnesium gluconate was divided in two parts, in which first part was kept untreated and termed as control sample. Besides, the second part was remotely treated by the renowned Biofield Energy Healer, Mr. Mahendra Kumar Trivedi with The Trivedi Effect®- Biofield Energy Healing Treatment and termed as Biofield Energy Treated sample. Consequently, both the samples were analyzed using PXRD, PSA, DSC, TGA/DTG, UV-Vis, and FT-IR analytical techniques. The PXRD analysis revealed that the crystallite sizes and relative peak intensities of the treated sample showed variations in the range of-25.01% to 185.79% and 6.99% to 32.99%, respectively along with 13.03% increase in average crystallite size as compared to the control sample. The particle sizes d10, d50, d90, and D(4,3) values of the treated sample were significantly decreased by 3.70%, 21.88%, 22.03%, and 21.16%, respectively, along with 10.75% increase in the surface area as compared to the control sample. The DSC studies showed minor decrease in melting point (0.10%) with 3.74% increase in the latent heat of fusion of the treated sample, compared to the control sample. Besides, The TGA/DTG analysis represented alterations in the weight loss pattern and maximum thermal degradation temperature (Tmax) of the treated sample. The analysis revealed three steps thermal degradation, in which the variation was observed from -6.79% to 10.14% in terms of weight loss along with 0.24% increase in the total weight loss of the treated sample, compared to the control sample. The Tmax of the first two peaks were found to be increased by 6.90% and 1.28%, while 3rd and 4th peaks were slightly decreased by 0.57% and 0.24% in the treated sample, compared to the control sample. The Energy of Consciousness Healing Treatment might produce a new polymorphic form of magnesium gluconate, which may have a better solubility, absorption and bioavailability profile along with altered thermal stability compared to the untreated sample. Thus, the Biofield Energy Treated magnesium gluconate would be helpful in designing the better nutraceutical/pharmaceutical formulations with better therapeutic responses against the magnesium deficiency.

Physical, Thermal and Spectroscopic Characterization of the Biofield Energy Treated Zinc Chloride

Zinc is an important mineral for humans due to its role as an immune-booster, antioxidant and enzyme regulator. Zinc deficiency impairs growth and immunity. Zinc chloride is given as a dietary supplement in cases of zinc deficiency. The current study aimed to analyze the impact of the Trivedi Effect®- Energy of Consciousness Treatment on the physical, thermal, and spectral properties of zinc chloride. The methodology included dividing the zinc chloride sample into two equal parts; followed by keeping one part untreated and named as the Control sample. The other part was termed as the Biofield Energy Treated sample, which was remotely treated for ~3 minutes by Mr. Mahendra Kumar Trivedi, who was located in the USA, while the test samples were located in the research laboratory in India. Both the samples were analyzed using PXRD, PSA, DSC, UV-Vis, and FT-IR analytical techniques. The PXRD analysis revealed alterations in the relative peak intensities and crystallite sizes of the Treated sample in the range of 52.69% to 1232.65% and -33.36% to 92.28%, respectively, along with 13.75% significant increase in average crystallite size, compared with the Control sample. Also, the Biofield Energy Treated sample showed a significant increase in the particle sizes d10, d50, d90, and D(4,3) values by 88.08%, 12.87%, 2.25%, and 9.13%, respectively, along with a 31.49% decrease in the surface area as compared to the Control sample. The DSC analysis revealed slight alterations in the melting and decomposition temperature of the Biofield Energy Treated sample by 0.59% and -1.22%, respectively; however, the latent heat of melting and decomposition significantly decreased by -7.41% and -68.41%, respectively, compared to the Control sample. Moreover, the FT-IR studies also revealed some alterations in the spectrum of the Biofield Energy Treated sample, as there were some additional peaks in the region of 650-1000 cm-1 and the Zn-Cl stretching peak was shifted to lower frequency i.e., 511 cm-1, compared to the Control sample (557 cm-1). The Energy of Consciousness Treatment may help in producing a new polymorphic form of zinc chloride, which may have better flowability, and storage parameters along with altered thermal stability compared to the untreated sample. Thus, the Biofield Energy Treated zinc chloride could be helpful in designing better nutraceutical, dietary supplements and/or pharmaceutical formulations to combat against zinc deficiency.

Structural and optical properties of Al-doped ZnO thin films produced by magnetron sputtering

Experimental and theoretical investigations of the structure and optical properties of Al-doped ZnO (AZO) thin films produced by magnetron sputtering under different values of electric current were conducted. The XRD results confirm the formation of the AZO thin films with hexagonal wurtzite structure, with preferential orientation along the crystallographic plane (002), direction c. The increment of electric current allowed an increase in average crystallite size. The FE-SEM and AFM images analyses of the AZO films revealed the occurrence of nucleation on the substrate surface that formed films with granular and rough structure. The higher substrate temperature caused by the higher value of electric current had influence on the grain size and thickness (ranging from 974 to 1500 nm) of the formed thin films. Due to the high absorption of free carriers, the optical transmittance of the AZO films was acceptable for the visible spectrum and limited to the near infrared region. The energy band gap values for both AZO films, measured from the optical transmission spectra, were ideal for semiconductor applications. The ab initio calculations using DFT and the method LSDA + U along with the correction of Hubbard were successfully applied to investigate the structural and optical effects. The band structures of the pure ZnO and ZnO:Al, calculated in this work, presented Eg values close to the experimental results. Therefore, these results imply that our methods are reliable and that the calculations are in accordance with the experimental results.

Microscopic investigations of morphology and thermal properties of ZnO thin films grown by atomic layer deposition method

This work presents the study of morphology and thermal properties of thin ZnO films fabricated by atomic layer deposition. The layers were deposited on n-Si(100) wafers at 200 °C. X-ray diffraction measurements showed the polycrystalline structure of the thin films with preferred (100) orientation. The thinner ZnO layers were fine grained, while the thicker films were formed with larger, elongated grains. Surface morphology parameters and the thermal conductivities were obtained from microscopic measurements. Thermal properties correlated with surface roughness of the ZnO thin films. Variations in thermal conductivity followed the changes in morphology of the layers. The mean surface roughness depended on the number of deposition cycles and varied from 1.1–2.6 nm. Thermal conductivity varied from 0.28 to 4.29 Wm−1K−1 and increased also with an increase of average crystallite size. The possible correlations between electrical conductivity and thermal conductivity were also analyzed. The phonon contribution to total thermal conductivity dominates over the electron thermal conductivity.

Probing the effect of selenium substitution in kesterite-Cu2ZnSnS4 nanocrystals prepared by hot injection method

In this paper, we report the effect of sulfur (S) substitution with selenium (Se) in CZTS nanocrystals prepared by hot injection method. The formation of kesterite-copper zinc tin sulfide (Cu2ZnSnS4, CZTS) and copper zinc tin selenide (Cu2ZnSnSe4, CZTSe) nanocrystals is confirmed by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) analysis. The XRD, TEM and atomic force microscopy (AFM) analysis shows an overall increase in average crystallite size upon Se substitution. AFM images revealed an increase in root mean square surface roughness (Sq) and average surface roughness (Sa) when S in CZTS is replaced by Se. The substitution of S by Se in host CZTS narrows the optical band gap from 1.56 to 1.03 eV. The ultraviolet photoelectron spectroscopy (UPS) analysis shows shift in valence band and conduction band edge in CZTSe compared to CZTS. The photocurrent density measurement in synthesized CZTSe thin films is ~ 4 to 5 times higher than CZTS thin films. The obtained results show that CZTSe can be a promising candidate as absorber material in photovoltaic applications.

Structural and magnetic properties of CuFe2O4 ferrite nanoparticles synthesized by cow urine assisted combustion method

Abstract Copper ferrite (CuFe2O4) nanoparticles were synthesized by sol–gel auto combustion method using cow-urine as a chelating agent. The obtained ferrite nanoparticles are heat treated at different temperatures (450 °C and 750 °C) in order to study their size dependent structural and magnetic properties. Energy Dispersive X-ray (EDX) spectra showed the maintenance of stoichiometry of elemental composition of ferrite system. Secondary phases of CuO and α-Fe2O3 are identified from the X-ray diffraction (XRD) patterns and these phases seem to be reducing with the heat treatment improving the ferrite phase of the sample. A systematic variation of structural parameters that is decrease of lattice parameter (8.379–8.369 A) and increase in average crystallite size (13.7–18.2 nm) have been found with the heat treatment. The average particle size estimated from Field Emission Scanning Electron Microscopy (FE-SEM) micrographs (14.5–22.3 nm) is slightly bigger than the average crystallite size estimated from XRD is due to the coalescence of crystallites which can be identified in FE-SEM micrographs. The obtained vibrational frequencies in the range of 550–450 cm−1 confirm the ferrite phase of copper ferrite. The splitting observed at the octahedral vibrational band is assigned to the secondary phase of α-Fe2O3. The saturation magnetization (Ms) is increasing with the heat treatment and highest value of Ms = 35.4 emu/g was reported. The results are discussed in terms of variation of particle sizes presuming the core–shell interactions.

RETRACTED ARTICLE: Surface morphology, optical properties and Urbach tail of spray deposited Co3O4 thin films

Cobalt oxide (Co3O4) thin films were deposited onto glass substrates by a simple spray pyrolysis technique using Co (CH3COO)2 .4H2O as a precursor material. The as-deposited films were characterized using field emission scanning electron microscope (FESEM) and UV–visible spectrophotometer. FESEM images showed uniform and well-aligned nanofiber growth of Co3O4 thin film. The average crystallite size was found to increase from 15 to 25 nm with the increase of substrate temperature. The increase in average crystallite size may be due to the agglomeration and recrystallization of cobalt oxide nanoparticles. The absorption peaks obtained at 355 nm and 540 nm were attributed to the transitions taking place between oxygen and cobalt charge transfer (O2− → Co3+ and O2− → Co2+). The energy band gap was found to decrease from 2.35 to 2.03 eV and Urbach energy (Eu) increased from 0.73 eV to 0.84 eV with the increased substrate temperatures from 250 °C to 350 °C. The optical absorption coefficient exhibited an exponential dependence of photon energy following Urbach’s rule, and Urbach tail was dependent on lattice defects. The direct band gap of the Co3O4 thin film clearly showed a red shift with increasing temperature and provided an absorption favorable for bio-sensing applications.

Anisotropy control in magnetic nanostructures through field-assisted chemical vapor deposition.

Chemical vapor deposition of iron pentacarbonyl (Fe(CO)5) in an external magnetic field (B = 1.00 T) was found to significantly affect the microstructure and anisotropy of as-deposited iron crystallites that could be transformed into anisotropic hematite (α-Fe2O3) nanorods by aerobic oxidation. The deterministic influence of external magnetic fields on CVD deposits was found to be substrate-independent as demonstrated by the growth of anisotropic α-Fe columns on FTO (F:SnO2) and Si (100), whereas the films deposited in the absence of the magnetic field were constituted by isotropic grains. TEM images revealed gradual increase in average crystallite size in correlation to the increasing field strength and orientation, which indicates the potential of magnetic field-assisted chemical vapor deposition (mfCVD) in controlling the texture of the CVD grown thin films. Given the facet-dependent activity of hematite in forming surface-oxygenated intermediates, exposure of crystalline facets and planes with high atomic density and electron mobilities is crucial for oxygen evolution reactions. The field-induced anisotropy in iron nanocolumns acting as templates for growing textured hematite pillars resulted in two-fold higher photoelectrochemical efficiency for hematite films grown under external magnetic fields (J = 0.050 mA cm−2), when compared to films grown in zero field (J = 0.027 mA cm−2). The dark current measurements indicated faster surface kinetics as the origin of the increased catalytic activity.

Effect of sintering temperature on structural, magnetic, magnetocaloric and critical behaviors of Ni-Cd-Zn ferrites prepared using sol-gel method

We have investigated the effect of sintering temperature on structural, magnetic, magnetocaloric and critical behaviors of Ni0.4Cd0.3Zn0.3Fe2O4 ferrites synthesized using sol-gel method at 900 °C and 1100 °C. X-ray diffraction patterns indicated that samples crystallize in the cubic spinel structure (Fd3‾m space group) with an increase of lattice constant and average crystallite size as the sintering temperature increases. Magnetic measurements revealed that that the prepared samples undergo second-order ferromagnetic (FM) to paramagnetic (PM) phase transitions. An increment in magnetization, Curie temperature, magnetic entropy change and relative cooling power has been observed with increasing the sintering temperature. The magnetic entropy change reached maximum values of about 1.11 J.kg−1.K−1 and 1.62 J.kg−1.K−1 for μ0H = 5 T corresponding to relative cooling power (RCP) of 152.09 J.kg−1 and 253.65 J.kg−1 for samples sintered at 900 °C and 1100 °C, respectively. These values are comparable favorably with those of some others ferrites considered as possible candidates for magnetic refrigeration. The estimated critical exponents obtained for sample sintered at 1100 °C are close to the tricritical mean-field model; whereas for sample sintered at 900 °C, the exponents belong to a different universality class. This change of critical exponents is mainly due to the increase of average crystallite size as the sintering temperature increases.

Thermally evaporated CZTSe thin films for solar cell application: Study on the effect of annealing time

ABSTRACTIn this paper, Cu2ZnSnSe4 (CZTSe) thin films were prepared by thermal evaporation method and annealed at 300°C for three different annealing time (2, 4, and 6 h) in air atmosphere. The XRD studies indicates that the as deposited films shows amorphous nature and annealed films confirms the formation of CZTSe compound and its average crystallite size increase with increase in annealing time. Among the films, the 2 h annealed film shows higher crystallinity. AFM images show bigger size particels for annealed films. DRS spectra of all the films show good optical absorption in the entire visible range and the band gap is found in the range of 1.45–1. 54 eV. Therefore the annealed films show good photosensing behavior.

Synthesis of ZrO2 nanoparticles using reactive magnetron sputtering and their structural, morphological and thermal studies

Intensive and extensive research is focused on the synthesis of ZrO2 nanoparticles being used in different applications such as photocatalysis, sensors, coatings and wastewater treatment. In the present work, we report the synthesis of ZrO2 nanoparticles using novel reactive magnetron sputtering technique and then investigated the sputtering power (40, 60, 80 and 100 W) effect on structural, morphological and thermal properties. The characterizations of the synthesized nanoparticles were carried using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray analysis (EDXA), Transmission electron microscopy (TEM), Selected area electron diffraction (SAED) and Thermogravimetry analysis (TGA). XRD analysis confirmed the formation of pure tetragonal phase with an increase in average crystallite size as a function of sputtering power. EDXA and Raman analysis also confirmed the formation of high purity tetragonal phase. FE-SEM and TEM results displayed spherical type morphology in aggregated form having a particle size less than 10 nm. TGA results indicated that the weight loss was only due to desorption of water molecules and is inversely proportional to the particle size.

Enhanced ethanol sensing performance for chlorine doped nanocrystalline LaFeO3-δ powders by citric sol-gel method

LaFeO3-xClx (x=0, 0.15, 0.3 and 0.6) powders were prepared by citric sol-gel method. On the whole, the introduction of chlorine dopant results in the increase of average crystallite size and grain size, the reduction of intrinsic resistance, and overall enhancement of ethanol sensing performance. The best gas response of 79.2–200ppm ethanol at prime working temperature of 136°C was achieved by the sensor with x=0.6, which exhibited superior ethanol sensing performance to other sensors with good stability, gas response, selectivity, short response and recovery time at prime working temperature. XRD and XPS results show that chlorine dopant mainly exists in the form of Fe-Cl bond in the lattice and on the surface, which are more favorable to form than the La-Cl bond either in the lattice or on the surface. ab initio calculations on the process of gas sensing to C2H5OH on FeO-terminated LaFeO3 (010) surface were performed under the guidance of XPS result, which indicate that the substitution of oxygen by chlorine both at the surface adsorption site and in the lattice should be responsible for the enhanced ethanol sensing performance of the chlorine doped LaFeO3.