Pechini Method Research Articles

Synthesis of weakly-agglomerated luminescent CaWO4:Nd3+ particles by modified Pechini method

The specific luminescence behavior of crystalline oxide particles doped with rare earth ions strongly depends on the initial composition of the host material and synthesis conditions. This issue is especially significant for non-isovalent doping in the crystal lattice. In this case, the formation of the structure is accompanied by the formation of point defects serving as charge compensators. The work is devoted to the synthesis of CaWO 4 :Nd 3+ particles in the salt melt (modified Pechini method) and the study of structural and luminescent properties under varying synthesis conditions. It was found that temperature and duration of heat treatment in the salt melt (KCl) affected the crystal structure, the size of coherent scattering regions, luminescence intensity, and lifetime. An increase of heat treatment temperature led to a reduction of luminescence intensity and lifetime due to the formation of point defects. The optimal synthesis conditions for obtaining the highest luminescence intensity of CaWO 4 :Nd 3+ crystalline particles in salt melt were found to be the following Т 1 = 600 °C; t 1 =2 h (the stage of polymer gel thermal treatment), Т 2 = 800 °C; t 2 =1 h (the stage of thermal treatment in KCl salt melt). As-synthesized CaWO 4 :Nd 3+ powders contain both coarse and fine fractions. However weak particle agglomeration allowed obtaining a water dispersion with individual nanoparticles (up to 200 nm) after ultrasonic treatment. According to the obtained results, the synthesized material is characterized by high luminescence intensity and high dispersion, and promising as fluorescent thermometers and biological labels.

Low temperature synthesis of Li0.33La0.55TiO3 solid electrolyte with Al3+ doping by a modified Pechini method

Low temperature synthesis of Li0.33La0.55TiO3 solid electrolyte with Al3+ doping by a modified Pechini method

Synthesis and Photoluminescence Properties of Pr3+-Doped Ba0.5Ca0.5TixZr(1-x)O3 Perovskite Diphasic Ceramics Obtained by the Modified Pechini Method.

The Pr3+-doped solid solutions from (Ba,Ca)(Ti,Zr)O3 (BCTZO) system were successfully synthesized using an efficient and low-energy consuming route—the Pechini method combined with the sintering at relatively low temperature (1450 °C). The obtained materials were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric properties were systematically studied. The Pr3+-doped BCTZO diphasic material generates intense and broad red photoluminescence (PL) emission at room temperature. The optical properties were significantly improved with the Ti4+ substitution by Zr4+ ions. As a result, the Pr3+-doped (Ba,Ca)(Ti,Zr)O3 ceramics is a promising candidate for environmentally friendly, multifunctional material by combining good dielectric and photoluminescent properties with prognosis for the manifestation of strong photoluminescent and mechanoluminescent effects.

Structural and morphological investigations of barium zirconium titanate particles synthesized by the Pechini method

Abstract Barium zirconium titanate systems are lead-free, environmentally friendly materials exhibiting relaxor behavior with increasing Zr content. Therefore, the study proposed preparing and characterization of an ecologically favorable Pb-free relaxor from Ba(Zr0.5Ti0.5)O3 (BZT). The results reported here are based on the research of BZT micrometric powders prepared by the Pechini method. The phase evolution was monitored by X-ray diffraction from 800 °C to 1300 °C, and results show that the formation of BZT starts around 1050 °C and continues until 1300 °C. The Rietveld refinement of data at 1300 °C confirms that BZT has a cubic structure. The thermal and structural properties of BZT samples were identified by thermogravimetric analysis and Fourier-transform infrared spectroscopy. Scanning electron microscopy results reveal that the synthesized particles are micron-sized (2–2.8 µm), rounded, polygonal-shaped, and agglomerated.

Electrocaloric Effect in Sodium Bismuth Titanate Based Ferroelectric Composites

Mixed system of (1-x)Na0.5Bi0.5TiO3+(x)SrTiO3 (NBT-ST) where x=0.075, 0.125, 0.150, 0.200 ferroelectric ceramic materials are synthesized using modified pechini method. These optimized compositions are used for study of polarization versus electric field (P-E) loops. The ferroelectric response of the samples is investigated as a function of temperature. Remnant polarization of exhibited loops observed to decrease with increasing temperature. PE data is used to estimate the electrocaloric properties. Maximum entropy change, full width at half maximum, relative cooling power is obtained from theoretical calculations.

Hybrid dual conductor on Ni‐rich NCM for superior electrochemical performance in Lithium‐ion batteries

To enhance the conductivity of cathode materials, we propose a surface modification of Li1.03(Ni0.88Co0.08Mn0.04)O2 (NCM) cathode materials with a high ionic conductor (Li1.3Al0.3Ti1.7[PO4]3, LATP) and a high electronic conductor (multi-walled carbon nanotubes, MWCNTs). In this study, a lithium-ion conductor with a structure similar to NASICON was successfully synthesized via a modified Pechini method. For the surface modification, a prepared nanosized LATP and a commercial Ni-rich NCM (Ni ≥80%) were combined by grinding them together. LATP-coated Ni-rich NCM exhibits a high diffusion level (2.144 × 10−6 cm2∙s−1) in the voltage range of 2.8 to 4.35 V at 25°C owing to increased ionic conductivity. Subsequently, MWCNTs, which are electrically conducting, are coated onto the LATP-coated Ni-rich NCM via a wet process. The electrochemical performance of the MWCNT/LATP dual-coated Ni-rich NCM was evaluated at 25°C and 45°C. The results demonstrate that the dual-coated Ni-rich NCM cathode materials exhibit a high discharge capacity, adequate rate capability, and stable cycling performance.

Synthesis and dielectric properties of K1.6Fe1.6Ti6.4O16 ceramics produced by the Pechini method

Potassium titanate modified with Fe3+ ions matching the stoichiometry of K1.6Fe1.6Ti6.4O16 (KFTO) was obtained by the polymer complex precursor method (Pechini method). The phase composition and morphology of the obtained sample were characterized using XRD, laser diffraction, and SEM technique. X-ray phase analysis shows single-phase formation of potassium titanate with a tetragonal hollandite-like structure. The Rietveld method was used to clarify the crystal lattice parameters. The parameters of the crystal lattice are: a = b = 10.1510 Å и c = 2.9659 Å. The results of SEM and laser diffraction showed that the particles of the studied nanopowder have a cubic shape and an average size of 400 nm. The dielectric properties in the frequency range of 0.1 Hz to 1.0 MHz were studied for ceramic disks obtained by sintering of compressed nanopowder at 1080 oC. It was found that ceramics based on KFTO solid solutions have high dielectric permittivity and low dielectric losses and characterized with increased polarizability. The high polarizability of the material is explained by the relatively high mobility of K+ ions in the tunnel of the considered hollandite structure that is accompanied by the redistribution of electrons in the crystal lattice. A discussion of the contribution of various processes to the permittivity is presented.

High CO2 resistance of indium-doped cobalt-free 60 wt.%Ce0.9Pr0.1O2-δ-40 wt.%Pr0.6Sr0.4Fe1-In O3-δ oxygen transport membranes

The oxygen transport membrane (OTM) has huge application prospects in gas separation and carbon neutralization based on oxygen enriched combustion. In this paper, the family 60 wt.%Ce0.9Pr0.1O2-δ-40 wt.%Pr0.6Sr0.4Fe1-xInxO3-δ (CPO-PSF1-xIxO, x = 0.01, 0.025, 0.05, 0.075, 0.1) cobalt-free dual-phase MIEC OTMs doped with indium have been successfully prepared by Pechini method. The phase structure, surface morphology, element distribution, oxygen permeability, and long-term operation stability of these OTMs are systematically explored. Among these OTMs, the champion oxygen permeable flux of CPO-PSF0.99I0.01O reaches 1.07 mL min−1·cm−2 and 0.80 mL min−1·cm−2 at 1000 °C under air/He gradient and air/CO2 gradient. Meanwhile, CPO-PSF0.99I0.01O maintains the value of 0.80 mL min−1·cm−2 steadily at 1000 °C for 100 h when pure CO2 as the sweep gas. The surface element distribution and phase structure of the OTMs after long-term oxygen permeability reaction are investigated by XRD, SEM combining with EDS, where the spent membranes retain the same structure and component as the fresh membranes, demonstrating that the In-doped OTMs have an excellent CO2 tolerance. Suitable indium substitution for iron of these OTMs not only improves the oxygen permeability, but also maintains the long-term reaction stability of the material.

Structural and Morphological Characterization of La0.9sr0.1fe0.9co0.1o3±Δ Perovskite Obtained by Pechini and Sonosynthesis Methods

Structural and Morphological Characterization of La0.9sr0.1fe0.9co0.1o3±Δ Perovskite Obtained by Pechini and Sonosynthesis Methods

Thermoelectric properties of CaMnO3 ceramics produced by using powder synthesized by modified Pechini method

Calcium manganate (CMO) is a promising n-type semiconductor for thermoelectric applications due to its intrinsic properties. Still, these properties are highly dependent on the processing route used to produce these materials. In this work, properties of the polycrystalline CMO ceramics are reported by studying samples obtained from powders synthesized by a modified Pechini method and sintered at 1543K for 1, 3, 6, 12 and 24 h. Crystallographic parameters of the resulting phases were determined from X-ray diffraction patterns. The ceramics sintered for 6 h has the highest density (94.8%TD), while the CMO-1h sample (sintered only 1 h) presented the lowest density (77.2%TD) due to a large amount of secondary phase and short sintering time. The crystallite sizes of the CMO particles reached 49.2 nm; meanwhile, the grain sizes were in the range from 1.04 to 4.85 ?m. Seebeck coefficient has a negative value, characterizing an n-type material, and its value approached ?350 ?V/K at 873K. The sample sintered for 1 h has the lowest value of thermal conductivity (3.3W/mK), while the ceramics sintered for 3 h reached maximum electrical conductivity value (1830 S/m), both at 873K. In addition, this high conductivity of the ceramics sintered for 3 h contributed to it having the highest ZT value of about 0.039.

Кинетика адсорбции и фотокаталитического разложения диазокрасителя нанокомпозитом ZnO-MgO

The synthesis of ZnO-MgO nanocomposite via modified Pechini method was performed. The crystalline structure and the morphology of nanocrystals were studied by X-ray diffraction analysis and scanning electron microscopy. The study on the kinetics of diazo dye adsorption and its photocatalytic decomposition on the surface of nanocomposite was performed. It was shown that the rate of adsorption process in aqueous solution is described by a kinetic equation of the first order. The application of the nanocomposite allows to significantly increase the efficiency of UV water treatment and its purification from the dye. However, a brief deviation of experimental data on the rate of photocatalytic degradation from the values of the widely used kinetic equation of the first order is observed.

Kinetics of adsorption and photocatalytic decomposition of a diazo dye by nanocomposite ZnO-MgO

The synthesis of ZnO-MgO nanocomposite via modified Pechini method was performed. The crystalline structure and the morphology of nanocrystals were studied by X-ray diffraction analysis and scanning electron microscopy. The study on the kinetics of diazo dye adsorption and its photocatalytic decomposition on the surface of nanocomposite was performed. It was shown that the rate of adsorption process in aqueous solution is described by a kinetic equation of the first order. The application of the nanocomposite allows to significantly increase the efficiency of UV water treatment and its purification from the dye. However, a brief deviation of experimental data on the rate of photocatalytic degradation from the values of the widely used kinetic equation of the first order is observed. Keywords: photocatalysis, adsorption, ZnO-MgO, nanocomposite, kinetics.

Synthesis of porous high-temperature superconductors via a melamine formaldehyde sacrificial template.

Nanostructured high-temperature superconductors YBa2Cu3O6+δ and Bi2Sr2CaCu2O8+δ were synthesised using a melamine formaldehyde sponge as a sacrificial template, via three solution-based approaches. In the case of YBa2Cu3O6+δ, a modified Pechini method produced a material with a superconducting transition at 92 K and a specific surface area of 4.22 m2 g−1. Further analysis with Hg porosimetry determined that the sponge exhibited a porosity of 82%. In the case of Bi2Sr2CaCu2O8+δ, this method produced a material that exhibited superconductivity at 86 K with a specific surface area of 9.62 m2 g−1. Hg-porosimetry determined that the BSCCO sponge exhibited a porosity of 78%.

Optimisation of high-performance, cobalt-free SrFe1-xMoxO3-δ cathodes for solid oxide fuel cells prepared by spray pyrolysis

Strontium-ferrite-based perovskites as cobalt-free cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) have been analysed employing structural, stability and electrochemical studies. Neutron diffraction of SrFeO3-δ and SrFe0.9Mo0.1O3-δ prepared by a Pechini method confirmed that SrFeO3-δ undergoes a phase transition from tetragonal to cubic symmetry at 300–400 °C, whereas Mo-doping stabilises cubic symmetry in the range RT-900 °C. Spray-pyrolysed electrodes offered significantly lower area-specific resistances of 0.2 and 0.11 Ω cm2 for SrFeO3-δ and SrFe0.9Mo0.1O3-δ at 700 °C, respectively, in comparison to their analogues synthesised by the Pechini method (0.55 and 0.42 Ω cm2), and lower grain size, as confirmed by scanning electron microscopy. Thermal cycling and ageing studies indicated a more robust response for the spray-pyrolysed electrodes, in particular the Mo-doped phase, which achieved a stable electrode-polarisation resistance <0.1 Ω cm2 for 10 heating/cooling cycles and 100 h of ageing at 700 °C. Anode-supported single cells with a thin Ce0.9Gd0.1O2-δ electrolyte produced performances of 0.5 and 0.9 W cm−2 at 700 and 800 °C, respectively. SrFe0.9Mo0.1O3-δ deposited by spray pyrolysis is, thus, proposed as a promising cobalt-free cathode for IT-SOFC based on its good structural stability and highly competitive electrochemical performance.

Highly water-soluble ternary citrato and malato lanthanide ethylenediaminetetraacetes with carbonate

Highly water-soluble dimeric lanthanum and cerium ethylenediaminetetraacetes with carbonate K8[Ln2(CO3)(Hcit)(EDTA)2]Cl·10.5H2O [Ln = La, 1; Ce, 2] and K6[Ln2(CO3)(Hmal)(EDTA)2]·12.5H2O [Ln = La, 3; Ce, 4] (H4cit = citric acid, H3mal = malic acid, and H4EDTA = ethylenediaminetetracetic acid) have been isolated from the reactions of lanthanide ethylenediaminetetraacetate with citric or malic acid and carbon dioxide in alkaline solution. The complexes have been well characterized by elemental analysis, IR, TG-DTG, 13C{1H} in solution and 13C-NMR spectra in solid state. X-ray structural analyses show that carbonates in 1 ∼ 4 are connected by two lanthanide EDTAs respectively, while the others are occupied by citrate or malate. 13C NMR spectra show obvious downfield shifts, indicating coordination of mixed-ligand lanthanides. The carbonates in 1 ∼ 4 are activated with bond distances 1.252(8) – 1.310(9) Å that are comparable to those [1.217(3) and 1.361(3) Å] in formic acid. The successful isolations of these complexes provide valuable species for mixed Pechini method in the constructions of lanthanide mixed-oxides.

Hydrogen production by thermochemical water splitting with La0.8Al0.2MeO3-δ (Me= Fe, Co, Ni and Cu) perovskites prepared under controlled pH

Aluminum based perovskites, La0.8Al0.2MeO3-δ (Me = Co, Ni, Fe, Cu), were synthesized following the Pechini method at different pHs and evaluated for hydrogen production by water splitting in a two-step thermochemical cycle. The pH of the synthesis medium showed a critical influence in the redox properties of the aluminum-based perovskites during the thermochemical cycle. Both the thermal reduction and the hydrolysis step produce irreversible changes in the crystalline structure of La0.8Al0.2MeO3-δ perovskites prepared at acid pH, avoiding the cyclability of the material and a stable production of hydrogen during consecutive cycles. However, these changes are not observed when the perovskites were synthesized at basic pH and operated at isothermal conditions at 800 ºC. In this case, the materials keep the crystalline structure leading to stable hydrogen production during consecutive cycles. Among all the studied materials, the nickel-based La0.8Al0.2NiO3-δ perovskites exhibited the best hydrogen productivity per cycle, 4.4 cm3 STP /gmaterial·cycle (Standard Temperature and Pressure conditions), which is a remarkable result considering that the thermochemical water splitting is conducted under isothermal conditions at just 800 ºC. Moreover, this result is accompanied with a good performance of the perovskite in terms of solar to fuel efficiency (being 0.46 the ratio between the potential energy recovery from the produced hydrogen and the solar heat required for its production), comparable or even higher than values reported in the literature for other metal oxides. These results confirm the La0.8Al0.2NiO3-δ perovskite as an auspicious material for a full-scale H2 production from water splitting by solar-driven thermochemical cycles at low temperatures.

Highly sensitive temperature reading from intensity ratio of Eu3+ And Mn4+emissions in Y3Al5O12 nanocrystals

Potential of Eu3+, Mn4+ co-doped YAG for dual-activated luminescence intensity ratio thermometry is investigated. The samples were prepared by modified Pechini method and cubic structure confirmed by X-ray diffraction with average crystallite size of ∼ 20 nm. Scanning electron microscopy revealed different sized chunks composed of ellipsoidal-shaped particles bellow 50 nm. Temperature-dependent photoluminescent emission spectra (λex = 465 nm, 98–473 K temperature range) of co-doped samples consist of emission bands in the red spectral region originating from both Eu3+and Mn4+transitions. Concentration of Mn4+ and Eu3+ is optimized to be 0.5mol% and 3mol%. Observed suppression of Eu3+ emission indicate an efficient (∼97%) energy transfer from Eu3+ to Mn4+. Using luminescence intensity ratio as the ratio between the integrated intensities of the Eu3+ 5D0→7F1 transition and the Mn4+ 2E→4A2manyfold, maximal absolute and relative sensitivities of SAmax = 19.2mK−1 at 351 K and SRmax = 5.06%K − 1 at 321 K were calculated.

Production of Complex Ceramic Films using domestic Inkjet Printers

The production cost is one of the issues for some complex ceramics applications, like the superconducting oxides. The main properties of such materials, i.e., zero electrical resistivity and perfect diamagnetism, make them attractive for several applications, including energy storage. Thus, in this work, we focus on the production and structural characterization of BSCCO superconducting films using a domestic inkjet printer. The precursor solution was prepared following Pechini's method, and it was used, such as the ink. Then, an E-shape film was printed over a SiO2 substrate. The results show that the sample produced with 12 depositions presented a superconducting transition at 81 K and a critical current density of 9.68 A/cm2 at 78 K.

A quantitative analysis of dicalcium silicate synthesized via different sol-gel methods

In this paper, the synthesis of dicalcium silicate (C2S) via sol-gel (acid-catalyzed) process including aqueous route, non-aqueous route, and the Pechini method is reported. The composition of C2S (α, β, and γ) polymorphs, by-products, and amorphous content is established by employing QXRD (quantitative X-ray diffraction) studies. The attention has been focused to comprehend assay-amorphous relationships of C2S yield. The intermediate dried gels have been investigated via thermal analysis to monitor changes in the gel structures and precursors at low temperatures. The synthetic parameters including calcination time and temperature, Ca/Si molar ratio and mode of cooling have been optimized to get pure β-C2S with low amorphous content. The dependency of β → γ C2S polymorphic transformation on mean crystallite size (Dcryst) is studied. Overall, the Pechini method exhibits the most promising results for the purity and tuning of β-C2S polymorph. Moreover, the non-aqueous and aqueous routes require calcining the dried gel at a temperature higher than 1200 ℃ due to the presence of CaO precursors as CaCO3. The theoretical calculations of amorphous content have revealed that the change in the stoichiometry from 2.0 to 1.7 Ca/Si ratio is not a viable solution to improve the C2S product yield.

M-type hexaferrites SrxBa1-xFe12O19 as new magnetic pigments: The role of cationic substitution on the magnetic and colour characteristics

Magnetic pigments composed of SrxBa1-xFe12O19 were prepared using a modified Pechini method. The influence of the calcination temperature and the composition of the solid solution on the structural, colorimetric, and magnetic properties were investigated. XRD patterns showed pigments crystallizing in a magnetoplumbite-type structure after calcination above 900 °C. The formation of α-Fe2O3 as a secondary phase was also observed in some compositions. Raman and Mössbauer spectroscopy indicated the presence of Fe in different coordination sites, which strongly influenced the magnetic and colorimetric properties of the pigments. A brown colour was obtained for all the magnetic pigments, with a higher saturation when calcination was performed at 900 °C. A meaningful increase in saturation was attained for the sample with a Sr0·50Ba0·50Fe12O19 composition, which was related to the short-range disorder and occupancy of Fe3+ cations at different sites. The addition of Sr2+ (up to x = 0.50) to the solid solution improved the intensity of the brown colour by increasing the a* and b* colour coordinates and decreasing L*. Magnetic measurements revealed saturation magnetization values of 56.8 emu g−1 for BaFe12O19. Upon the addition of Sr2+, an increase in the ferromagnetic behaviour was observed for barium-containing pigments, which indicates the possibility of their use as magnetic pigments in high-density recording media or paints for construction.