Deposition of Diamondlike Carbon Film and Mass Spectrometry Measurement in CH4/N2 RF Plasma

The deposition of diamondlike carbon (DLC) film and the measurements of ionic species by means of mass spectrometry were carried out in a CH₄/N₂ RF (13.56 MHz) plasma at 0.1 Torr. The film deposition rate greatly depended on both CH₄/N₂ composition ratio and RF power input. It was decreased monotonically as CH₄ content decreased in the plasma and then rapidly diminished to negligible amounts at a critical CH₄ content, which became large for higher RF power. The rate increased with increasing RF power, reaching a maximum value in 40% CH₄ plasma. The predominant ionic products in CH₄/N₂ plasma were NH⁺ ₄ and CH₄N⁺ ions, which were produced by reactions of hydrocarbon ions, such as CH⁺ ₃, CH⁺ ₂, CH⁺ ₅, and C₂H⁺ ₅ with NH₃ molecules in the plasma. It was speculated that the production of NH⁺ ₄ ion induced the decrease of C₂H⁺ ₅ ion density in the plasma, which caused a reduction in higher hydrocarbon ions densities and, accordingly, in film deposition rate. The N⁺ ₂ ion sputtering also plays a major role in a reduction of film deposition rate for relatively large RF powers. The incorporation of nitrogen atoms into the bonding network of the DLC film deposited was greatly suppressed at present gas pressure conditions.     

Ethylene Epoxidation in an AC Dielectric Barrier Discharge Jet System

In this work, ethylene epoxidation was investigated in a dielectric barrier discharge jet (DBDJ) with a separate ethylene/oxygen feed under oxygen lean conditions. The ethylene (C₂H₄) stream was directly injected behind the plasma zone in order to reduce all undesired reactions, including C₂H₄ cracking and further reactions, while the oxygen (O₂) balanced with argon was fed through the plasma zone totally to maximize the formation of active oxygen species. The effects of various operating parameters, such as total feed flow rate, O₂/C₂H₄ feed molar ratio, applied voltage, input frequency, and C₂H₄ feed position on the ethylene epoxidation activity, were investigated to determine the optimum operating conditions for this new DBDJ system. The highest ethylene oxide (EO) selectivity (55.2 %) and yield (27.6 %), as well as the lowest power consumption (3.3 × 10^?21 and 6.0 × 10^?21 Ws/molecule C₂H₄ converted and EO produced, respectively) were obtained at a total feed flow rate of 1,625 cm³/min (corresponding to a residence time of 0.022 s), an O₂/C₂H₄ feed molar ratio of 0.25:1, an applied voltage of 9 kV, an input frequency of 300 Hz, and a C₂H₄ feed position of 3 mm behind the plasma zone. The superior activity of the ethylene epoxidation in the DBDJ system resulted from a small reaction volume as well as a separate ethylene/oxygen feed.     

Laser-Assisted Chemical Vapor Deposition of Boron

Ar⁺ laser-induced chemical vapor deposition (LCVD) of B from gaseous mixtures of BCl₃ and H₂ has been investigated for temperatures between 1000 K and 2250 K and for partial pressure within the ranges 25 mbar ≤ p(BCI₃) ≤ 800 mbar and 10 mbar ≤p(H₂) ≤ 400 mbar. For the lowest temperatures, deposition is controlled by the chemical kinetics which, with p(BCI₃) = p(H₂) = 100 mbar, is characterized by an apparent chemical activation energy of about 26.5 kcal/mol. In this regime, the deposited boron is amorphous. At high temperatures, deposition becomes limited by gas-phase transport and polycrystalline boron with βrhombohedral structure is obtained.     

Rotating Gliding Arc Assisted Water Splitting in Atmospheric Nitrogen

In this study, hydrogen production from water splitting in N₂ using an atmospheric pressure rotating gliding arc plasma was investigated. The effect of input H₂O concentration and total flow rate on the performance of the plasma water splitting process (e.g., H₂ and O₂ yield, H₂ production rate, and energy yield of H₂) was investigated. N₂ showed a pronouncedly facilitating effect on the H₂O splitting and H₂ production process due to the reactions of the excited N₂ species [e.g., electronically excited metastable N₂(A)] with the H₂O molecules. The maximum H₂ production rate reached up to 41.3 μmols^?1, which is much higher than that of other typical non-thermal plasmas (e.g., ~0.2 μmols^?1 for a dielectric barrier discharge). Optical emission diagnostics has shown that in addition to the NO, N₂, and N₂ ⁺ that were observed in the pure N₂ spectra, strong OH and NH emission lines also appeared in the H₂O/N₂ spectra. OH radical is considered as a key intermediate species that could contribute to the formation of H₂, O₂, and H₂O₂. The increase of the H₂O concentration could lead to a continuous enhancement of the OH intensity. The rotational temperature of N₂ ⁺ dropped drastically from 2875 ± 125 to 1725 ± 25 K with the addition of 1 % (mol/mol) H₂O into the N₂ plasma.     

Characterization of Tin(IV) Oxide Thin Films Prepared by Atmospheric Pressure Chemical Vapor Deposition of cis‐[SnCl4{OC(H)OC2H5}2]

A new single‐source precursor, [SnCl₄{OC(H)OC₂H₅}₂], prepared by treating tin tetrachloride with ethyl formate (1:2 ratio) was developed for the deposition of tin oxide thin films on glass substrates. The compound [SnCl₄{OC(H)OC₂H₅}₂] is highly volatile and provides very high growth rates (up to 100Å s^?1 at 560 °C) in an atmospheric pressure chemical vapor deposition (APCVD) reactor. More significantly, the compound does not decompose to tin oxide below 320 °C, thereby minimizing the formation of particles in the vapor above the growing tin oxide film. To prepare highly conducting fluorine doped tin oxide (SnO₂:F) films 2,2,2‐trifluoroethyl trifluoroacetate was used as the source of fluoride. High quality SnO₂:F films were deposited at 560 °C with a flow rate of 2 mL fluoride reagent hr^?1; typical film properties are resistivity of 5.9 X 10^?4 Ω cm, Hall mobility of 27.3 cm² V^?1 s^?1, carrier concentration of 3.9 X 10²⁰ cm^?3 and percent transmission ranging from 86 to 88 %. The best films of SnO₂:F possess transparencies as high as 90 % (750 nm), sheet resistances as low as 7 Ω sq^?1 and Haacke's figure of merit as high as 29 X 10^?3 (750 nm). The newly developed APCVD reactor and the chemistry were optimized with respect to structural, electrical and optical properties of the films by adjusting the substrate temperature, gas flow rates and the amount of fluoride present in the vapor stream. Growth rates with respect to deposition time, substrate temperature and flow rates of precursors were found to be similar for both undoped (SnO₂) and doped (SnO₂:F) samples. The SnO₂:F films possess larger grains than the SnO₂ which may account for the lower resistivity and the higher mobility in the SnO₂:F samples.     

微波复合直流等离子体转化天然气制乙炔的研究

利用微波复合直流等离子体对天然气转化制乙炔反应进行了研究. 考察了氢烷比、气体流量、功率等参数对装置的能量利用率以及天然气转化反应的影响, 并考核了微波复合直流等离子体转化天然气制乙炔工艺的稳定性. 实验结果表明: 微波复合直流等离子体装置的能量利用率随等离子体工作气体的流量的增加而提高; 由于微波的作用使传统直流柱状等离子体分化为多根丝状等离子体, 从而使得电极的烧蚀方式由传统的点烧蚀变为面烧蚀, 并大幅度提高等离子体转化天然气工艺的稳定性和电极寿命; 甲烷的转化率和乙炔的收率随功率的增加而提高, 随CH₄/H₂比和气体流量的增加而降低, 在氢烷比为0.9、总气体流量为760 L/min、微波源输出电功率6 kW、直流电源输出功率90 kW时, 甲烷转化率可达84.4%, 乙炔选择性为75.6%, 乙炔收率为63.8%, 乙炔能耗达10.8 kWh•kg^－1; 电极寿命超过200 h.     

Kinetics and mechanism of the substitution reactions of some monofunctional Pt(II) complexes with heterocyclic nitrogen donor molecules. Crystal structure of [Pt(bpma)(pzBr)]Cl2·2H2O

Substitution reactions of [Pt(terpy)Cl]⁺ (terpy = 2,2′;6′,2′′-terpyridine), [Pt(bpma)Cl]⁺ (bpma = bis(2-pyridylmethyl)amine), [Pt(dien)Cl]⁺ (dien = diethylenetriamine or 1,5-diamino-3-azapentane) and [Pt(tpdm)Cl]⁺ (tpdm = tripyridinedimethane) with nitrogen donor heterocyclic molecules, such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr) and imidazole (Im), were studied in aqueous 0.10 M NaClO₄ in the presence of 10 mM NaCl using variable-temperature UV–vis spectrophotometry. The second-order rate constants k₂ indicate decrease in reactivity in the order [Pt(terpy)Cl]⁺ > [Pt(bpma)Cl]⁺ > [Pt(tpdm)Cl]⁺ > [Pt(dien)Cl]⁺. The most reactive nucleophile among the heterocyclic compounds is imidazole, while pzI shows slightly higher reactivity than pzBr. Activation parameters were also determined and the negative values for entropies of activation, ΔS^≠, support an associative mode of substitution for all substitution processes. Crystal structure of [Pt(bpma)(pzBr)]Cl₂·2H₂O was determined by single-crystal X-ray analysis. The coordination geometry of the complex is distorted square-planar while the bond distance Pt–N2(pzBr) is longer than the other three Pt–N distances.     

Anion encapsulation by Ln(III)/K(I) heterobismetal-capped cucurbit[5]uril

Three Ln(III)/K(I) (Ln = La, Ce and Nd) heterobismetal-capped cucurbit[5]uril molecular capsules, {[LaK(C₃₀H₃₀N₂₀O₁₀)Cl]Cl(H₂O)₃}Cl₂·8H₂O (1), {[CeK(C₃₀H₃₀N₂₀O₁₀)Cl]Cl(H₂O)₃}Cl₄(H₃O)₂ ^2 + ·8H₂O (2) and {[NdK(C₃₀H₃₀N₂₀O₁₀)Cl]Cl(H₂O)₃}Cl₂·12.5H₂O (3), were synthesised by self-assembly in aqueous solution, and their anion encapsulation property was confirmed by X-ray crystallography. The effect of the lanthanide cation radius on the structure of the heterobismetal-capped cucurbit[5]uril molecular capsules has been investigated.     

Synergetic effect of Prussian blue film with gold nanoparticle graphite–wax composite electrode for the enzyme-free ultrasensitive hydrogen peroxide sensor

Enzyme-free amperometric ultrasensitive determination of hydrogen peroxide (H₂O₂) was investigated using a Prussian blue (PB) film-modified gold nanoparticles (AuNPs) graphite–wax composite electrode. A stable PB film was obtained on graphite surface through 2-aminoethanethiol (AET)-capped AuNPs by a simple approach. Field emission scanning electron microscope studies results in formation of PB nanoparticle in the size range of 60–80 nm. Surface modification of PB film on AET–AuNPs–GW composite electrode was confirmed by Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy studies. Highly sensitive determination of H₂O₂ at a peak potential of ?0.10 V (vs. SCE) in 0.1 M KCl PBS, pH?=?7.0) at a scan rate of 20 mVs^?1 with a sensitivity of 23.58 μA/mM was observed with the modified electrode using cyclic voltammetry. The synergetic effect of PB film with AuNPs has resulted in a linear range of 0.05 to 7,800 μM with a detection limit of 0.015 μM for H₂O₂ detection with the present electrode. Chronoamperometric studies recorded for the successive additions of H₂O₂ with the modified electrode showed an excellent linearity (R ²?=?0.9932) in the range of 4.8?×?10^?8 to 7.4?×?10^?8 M with a limit of detection of 1.4?×?10^?8 M. Selective determination of H₂O₂ in presence of various interferents was successfully demonstrated. Human urine samples and stain remover solutions were also investigated for H₂O₂ content.     

Simultaneous Removal of H<Subscript>2</Subscript>S and Dust in the Tail Gas by DC Corona Plasma

The removal of hydrogen sulfide and dust simultaneously by the DC corona discharge plasma with a wire-cylinder reactor was studied at atmospheric pressure and room temperature. The outlet gases were analyzed by Fourier Transform Infrared. Chemical compositions of the dust collected from ground electrode were analyzed by X-ray fluorescence. The results showed that the DC corona discharge is effective in removing H₂S and dust simultaneously. The best H₂S conversion was gained with the 2 cm discharge gap. The lower inlet H₂S concentration, the higher conversion efficiency was gained at any specific input energy (SIE), while the energy yield was on the contrary. The removal efficiency of H₂S decreased gradually as oxygen concentration increased, which means that the H₂S decomposition mainly depends on direct electron collisions or short-living species, such as^·O, ^·OH radicals in the non-thermal plasma. At the initial stage, the conversion efficiency of H₂S increased with the increasing of relative humidity, but later decreased while the relative humidity keep increasing with the same SIE. Existing of dust can not only reduce the energy consumption of H₂S conversion and improve the removal efficiency, but also inhibit the yield of SO₂ for it can further react with some compounds in the dust. With the discharge gap of 2 cm, inlet H₂S concentration of 2400 ppm, O₂ Of 0.5 %, relative humidity of 41 %, dust content of 4000 ± 5 % mg/m³ and SIE of 600 J/L, the H₂S conversion reached 98.8 %, and the dust removal efficiency was close to 100 %.     

Study the effect of inorganic salts on the chemically polymerized aniline films using quartz crystal microbalance

The chemical oxidation of aniline with ammonium peroxydisulfate to form polyaniline (PANI) films has been studied in different aqueous acid mediums such as HCl, HNO₃, and H₂SO₄. The yield and the growth rate of the PANI film deposition were measured using the quartz crystal microbalance (QCM) technique. The effect of different salts such as KCl, NaNO₃, and K₂SO₄ and their concentration on the yield and the growth rate of the film formation are investigated. The yield of PANI film deposition depends on the acid used and the type of salts as well as their concentrations. When HCl and HNO₃ were used as media, the addition of salts with the same anion has no effect. However, when H₂SO₄ was used as media, the addition of salts with the same anions as the medium enhances the yield of PANI film deposition. The UV–visible spectra of the produced PANI films in the absence and presence of the salts are also studied. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of Light/Dark Regimens on Hydrogen Production by <Emphasis Type="Italic">Tetraselmis subcordiformis</Emphasis> Coupled with an Alkaline Fuel Cell System

To improve the photoproduction of hydrogen (H₂) by a green algae-based system, the effect of light/dark regimens on H₂ photoproduction regulated by carbonyl cyanide m-chlorophenylhydrazone (CCCP) was investigated. A fuel cell was integrated into a photobioreactor to allow online monitoring of the H₂ evolution rate and decrease potential H₂ feedback inhibition by consuming the generated H₂ in situ. During the first 15 h of H₂ evolution, the system was subjected to dark treatment after initial light illumination (L/D = 6/9 h, 9/6 h, and 12/3 h). After the dark period, all systems were again exposed to light illumination until H₂ evolution stopped. Two peaks were observed in the H₂ evolution rate under all three light/dark regimens. Additionally, a high H₂ yield of 126 ± 10 mL L^?1 was achieved using a light/dark regimen of L 9 h/D 6 h/L until H₂ production ceased, which was 1.6 times higher than that obtained under continuous illumination. H₂ production was accompanied by some physiological and morphological changes in the cells. The results indicated that light/dark regimens improved the duration and yield of H₂ photoproduction by the CCCP-regulated process of Tetraselmis subcordiformis.     

Ternary and binary copper(II) complexes: synthesis,characterization, ROS-inductive,proteasome inhibitory,and anticancer properties

Three ternary copper(II) complexes, [Cu(phen)(L-phe)Cl]·2H₂O, [Cu(phen)(L-leu)Cl]·4½H₂O, and [Cu(phen)(L-tyr)Cl]·3H₂O, and four binary copper(II) complexes, [Cu(phen)Cl₂]_, Cu(L-phe)₂·½H₂O, Cu(L-leu)₂·½H₂O, and Cu(L-tyr)₂·H₂O (where phen = 110-phenanthroline, L-phe = L-phenylalanine, L-tyr = L-tyrosine, L-leu = L-leucine and Cl^- = chloride), were synthesized and characterized by elemental analysis, spectroscopic techniques (FTIR, UV–visible, fluorescence spectroscopy), magnetic susceptibility, molar conductivity, and lipophilicity measurement. X-ray diffraction determination of a single crystal of [Cu(phen)(L-tyr)Cl] showed two independent molecules in the asymmetric unit, each with the same distorted square pyramidal geometry about copper(II). p-Nitrosodimethylaniline assay revealed that the three ternary complexes were better inducers of reactive oxygen species over time than binary complexes, CuCl₂, and free ligands. All the copper(II) complexes in this series inhibited the three proteolytic activities in the order Trypsin-like > Caspase-like > Chymotrypsin-like. In terms of anticancer properties, the copper(II)-phen complexes had GI50 values of less than 4 μM against MCF-7, HepG2, CNE1 and A549 cancer cell lines, more potent than cisplatin.     

Pyrolysis of Hailar lignite in an autogenerated steam agent

An in situ pyrolysis process of high moisture content lignite in an autogenerated steam agent was proposed. The aim is to utilize steam autogenerated from lignite moisture as a reactant to produce fuel gas and additional hydrogen. Thermogravimetric analysis revealed that mass loss and maximum mass loss rate increased with the rise of heating rates. The in situ pyrolysis process was performed in a screw kiln reactor to investigate the effects of moisture content and reactor temperature on product yields, gas compositions, and pyrolysis performance. The results demonstrated that inherent moisture in lignite had a significant influence on the product yield. The pyrolysis of L _R (raw lignite with a moisture content of 36.9 %, wet basis) at 900 °C exhibited higher dry yield of 33.67 mL g^?1 and H₂ content of 50.3 vol% than those from the pyrolysis of the predried lignite. It was also shown that increasing reaction temperature led to a rising dry gas yield and H₂ yield. The pyrolysis of L _R showed the maximum dry yield of 33.7 mL g^?1 and H₂ content of 53.2 vol% at 1,000 °C. The LHV of fuel gas ranged from 18.45 to 14.38 MJ Nm^?3 when the reactor temperature increased from 600 to 1,000 °C.     

Polyoxidovanadate complexes: synthesis,structures and catalytic oxidative bromination of phenol red

By selecting appropriate ligands, two polyoxidovanadate complexes, [Ni(en)₂]₃[V₁₈O₄₂Cl]·7H₂O·2H₃O⁺ (1) and [H₂N(CH₃)₂]₃[PV₁₄O₄₂]·2TMP·6H₃O⁺ (2), have been synthesized at different pH values using V₂(SO₄)₃, Ni(CH₃COO)₂, and H₆TTHA (for 1), VO(acac)₂ and TPP (for 2) (en = C₂H₈N₂, TPP = thiamine pyrophosphate, TMP = thiamine monophosphate, H₆TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid). The complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TG), and single crystal X-ray diffraction. The complexes catalyze the oxidation of the organic substrate phenol red in the presence of H₂O₂ and bromide, and the reaction system is considered as a model for hydrogen peroxide determination. The reaction rate constants (k) for 1 and 2 are calculated as 3.729 × 10³ and 4.083 × 10³ (mol L)^?2 s^?1. The maximum conversion rate of phenol red for 1 is 83.32%, while for 2 is 81.12%.     

Calcium coordination compounds based on phenoxyacetic acids: microwave synthesis,thermostability and influences on the crystal structures of chlorine substituent group on ligands

Three calcium coordination compounds, [Ca(CPA)(H₂O)₄]·(CPA), 1, [Ca(MCPA)₂(H₂O)₂]·H₂O, 2, and [Ca(TCPA)₂(H₂O)₃]·2H₂O, 3 [HCPA = 3-chlorophenoxyacetic acid, HMCPA = 2-methyl-4-chlorophenoxyacetic acid, and HTCPA = 2,4,6-trichlorophenoxyacetic acid], have been synthesized by the microwave method with advantages that include shorter reaction times, lower energy consumption, and higher product yield. The structures have been characterized by IR, elemental analysis, and single-crystal X-ray diffraction. Influences on the crystal structures by changing the number and position of chlorine substituent group in phenoxyacetic acid are discussed. Steric hindrance effects involving the Cl and an ability to form the O–H?Cl hydrogen bonds enrich the structure diversity. TG analysis reveals that the thermostability for the three compounds is 3 > 1 > 2, which could be influenced by the existence of hydrogen bonds (O–H?Cl and O–H?O).     

Deposition of platinum monolayers on gold

Deposition of small amount of Pt is reported onto polycrystalline Au from H₂PtCl₆-containing solutions. Spontaneous deposition, yielding about 5% of a full-packed monolayer, has been found at the steady-state open circuit potential. Formation of a somewhat more dense, but still a partial monolayer could be observed at potentials between the steady-state open circuit potential and that of the onset of bulk deposition. A specific difference of monolayer and bulk deposition is that Pt surface area levels off with time and keeps increasing for the former and latter types of deposition, respectively. Pt monolayers with quite high coverages can be formed in a rather narrow, 20–30 mV potential region only. The surface areas of Pt and of the Pt-free Au have been simultaneously measured as cyclic voltammetry peak charges. From these measurements, the site requirement of the Pt atoms was determined to be around four; that is, each Pt atom blocks the oxidation of about four underlying/neighbouring Au atoms, implying their distant positions. Based on the results, Au surfaces coated with monoatomic Pt layers of quite high coverages can be prepared.

     

α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films by liquid phase deposition: low-cost option for supercapacitor

In the present study, iron oxide (α-Fe₂O₃) thin films with good adhesion on stainless steel substrates are deposited by liquid phase deposition (LPD) technique, which is additive and binder-free. Iron oxyhydroxide (FeOOH) thin films are formed by means of a ligand-exchange equilibrium reaction of metal-fluoro complex ions and an F^?ions consuming reaction by using boric acid (H₃BO₃) as a scavenging agent. These films are annealed at 500 °C to get α-Fe₂O₃ thin films. The transformation from hydrophobic to hydrophilic nature of the films is observed due to annealing. The films are characterized by different techniques. The α-Fe₂O₃ film is checked for electrochemical supercapacitive performance in Na₂SO₃ solutions of various concentrations. Specific capacitance is calculated from cyclic voltammetry at numerous scan rates (5–200) mV s^?1. The highest obtained value of specific capacitance is 582 F g^?1 at 5 mV s^?1 for 0.5 M Na₂SO₃ electrolyte. The maximum values of specific power and specific energy are 6.9 and 53.4 Wh kg^?1 from the charge-discharge curve at the current density 2 mA cm^?2 in 0.5 M Na₂SO₃ electrolyte.     

Synthesis and crystal structures of two new uranyl coordination compounds obtained in aqueous solutions of 1-butyl-2,3-dimethylimidazolium chloride

Abstract

Two new uranyl coordination compounds, [C₉H₁₇N₂]₃[(UO₂)₂(CrO₄)₂Cl₂(H₂O)₂]Cl·5H₂O (1) and (C₉H₁₇N₂)[(UO₂)(C₂O₄)Cl] (2), have been synthesized by adding potassium dichromate (K₂Cr₂O₇) or oxalic acid dihydrate (H₂C₂O₄·2H₂O) solution into an aqueous solution of uranyl nitrate and 1-butyl-2,3-dimethylimidazolium chloride [Bmmim]Cl. [Bmmim]Cl provides the charge balance and Cl ions that coordinate with uranyl ions. The fundamental building units of 1 and 2 are UO₆Cl pentagonal bipyramidal structures. Compound 1 exhibits a graphene-like structure with a system molar ratio of 1:1 for U:Cr and crystallizes in the orthorhombic space group Pbca, with a = 25.644(3) Å, b = 12.996(14) Å and c = 29.198(4) Å. 16-Membered rings are formed by CrO₄^2? and UO₂²⁺ in the crystal structure of 1. Compound 2 crystallizes in monoclinic space group P2₁/n, with a = 10.759(3) Å, b = 11.395(3) Å, c = 14.149(4) Å, β = 102.962(9)° and shows one-dimensional (1D) serrated chains. Within the crystal structures of 1 and 2, C–H_[Bmmim]Cl?O hydrogen bonds are identified. O–H_water?Cl hydrogen bonds are also detected in the crystal structure for 1.     

All alkoxide route to manganate and coboltate perovskite films and powders: effects of processing parameters

Manganate and cobaltate perovskites having the general formula ABO₃ have many technologically important applications. Here we present all alkoxide based routes to manganate and coboltate perovskite films and nano-phase powders of the compositions; LCMO (La_0.67Ca_0.33MnO₃), LSMO (La_0.75Sr_0.25MnO₃), LNCMO (La_0.33Nd_0.33Ca_0.33MnO₃), LBSMO (La_0.75Ba_0.125Sr_0.125MnO₃) and LSCO (La_0.50Sr_0.50CoO₃). The Mn and Co (oxo) methoxy-ethoxide precursors were prepared by reaction of MnCl₂ or CoCl₂ with 2 Kmoe in methoxy-ethanol-toluene. After hydrolysis of the alkoxide solutions by atmospheric air all systems produced X-ray and electron diffraction amorphous gels of high elemental homogeneity, and the IR spectra showed that they consisted of hydrated oxo-carbonates. Heating in air resulted in similar weight-loss curves for all studied gels passing; loss of H₂O in the range 20–300 °C, decomposition of carbonate groups into oxide and CO₂ in the temperature range 300–700 °C, and in some cases loss of a small amount of oxygen in the temperature range 700–1,000 °C. The pure perovskites were obtained at 690–770 °C with heat rates of typically 5–20 °C min^?1 without annealing. Perovskites could also be obtained at 550 °C by annealing, but these perovskites are prone to be A-site ion inhomogeneous according to the TEM EDS studies, which was not the case for the perovskites heat-treated to at least the carbonate decomposition temperature. This A-site inhomogeneity is ascribed to sequential decomposition of carbonates due to their different thermal stabilities, which is probably a general feature also with other sol–gel precursors and low temperature annealing. High quality polycrystalline films were prepared on Si/SiO₂/TiO₂/Pt substrates with all compositions and high quality epitaxial films were prepared of LCMO (on 100 LaAlO₃) and LSCO (on 100 SrTiO₃). The colossal magneto resistance (CMR) of the epitaxial LCMO films of 32% (246 K) is in parity with PLD derived films. The conductivities of the epitaxial and polycrystalline LSCO films were 1.9 mΩcm (on STO) and 1.7 mΩcm (on α-Al₂O₃, respectively).