Polymerized Complex Method Research Articles

Luminescent properties of Pr3+-doped SrZrO3 phosphors

In this work Sr1-1.5xPrxZrO3 phosphors with different Pr3+ contents were synthesized by polymerizable complex and high-temperature solid-state methods. The samples were calcined between 700–1400°C. The crystal structure, microstructure and photoluminescence properties of the prepared powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy, respectively.The relationship between luminescent properties and the different sintering temperatures was studied. It was found that calcination at high temperature may remarkably increase the luminescence for samples synthesized by both methods. Emission spectra for all samples show dominant bands ascribed to transitions from the 3P0,1 energy levels to lower levels, particularly that one in the greenish-blue region, corresponding to the 3P0 → 3H4 transition. However, the bands ascribed to the 3P0,1 → 2S+1LJ transitions corresponding to the red spectral region are not inhibited at all, in contrast to recent reports. The samples prepared by solid state method exhibit a charge transfer band (CTB) due to the presence of Ti4+ impurities.

錯体とポリマーからセラミックスをつくる : 錯体重合法の原理と実際( 話題を探る)

錯体とポリマーからセラミックスをつくる : 錯体重合法の原理と実際( 話題を探る)

A new silver niobate photocatalyst AgNb13O33: Synthesis, structure and photochemical properties

Ag-containing niobate AgNb13O33 has been prepared by the sol–gel polymerized complex method. The structure was investigated via a good XRD Rietveld refinement in a typical perovskite-like framework. The morphological properties of the AgNb13O33 nanoparticles were tested via transmission electron microscopy (TEM), scanning electron microscope (SEM), and energy dispersive spectra (EDS) measurements. AgNb13O33 is a typical direct allowed semiconductor with band energy of 2.81 eV, which is much narrower than 3.4 eV of Nb2O5. This silver niobate can harvest both UV and near UV light, which is benefited from the (O-2p/Ag-4d) hybridization in the valence band. The photocatalytic abilities of AgNb13O33 nanoparticles were reported. The sample presents more efficient photocatalytic effects on photo-degradation of methylene blue (MB) dye solutions than that of Nb2O5. The photocatalytic mechanism was discussed on band energy levels, trapping experiments, photoluminescence and the decay lifetime.

Mössbauer study of zinc-substituted strontium cobalt Z-type hexaferrite

Polycrystalline powder samples of the zinc-substituted strontium cobalt Z-type hexaferrite: Sr3Co2-xZnxFe24O41 (x = 0, 0.5, 1.0, 1.5 and 2.0) were prepared by the polymerizable complex method. Their Mossbauer spectra were measured at room temperature with conventional constant-acceleration spectrometer. Obtained Mossbauer spectra were numerically separated into six discrete components. The relationship between Mossbauer parameters and magnetic properties has been discussed. From the values of the isomer shift, it was found that the iron ion in Sr3Co2-xZnxFe24O41 is trivalent with high spin. The value of the quadrupole splitting increased and changed the sign from negative to positive for the sample with x = 1.5. From the results mentioned above and the analysis of the complex permeability spectra, the magnetocrystalline anisotropy of Sr3Co2-xZnxFe24O41 is changed from c-plane to c-axis at Zn content between x = 1.0 and 1.5. The compositional dependence of the areas of each subspectra showed that Zn2+ ions occupy the sites with down spin at the compositional range of x = 0.0–1.0.

Amino Acid-Aided Synthesis of a Hexagonal SrMnO3 Nanoperovskite Catalyst for Aerobic Oxidation.

A simple and efficient synthetic method for preparing high-surface-area perovskites was investigated by focusing on the importance of the formation of an amorphous precursor. Hexagonal SrMnO3 with high surface area was successfully synthesized by simple calcination of the amorphous precursor prepared using aspartic acid and metal acetates instead of metal nitrates, without pH adjustment. The specific surface area reached up to ca. 50 m2 g–1, which is much larger than that for SrMnO3 synthesized by previously reported methods. The catalytic activity for heterogeneous liquid-phase aerobic oxidation was significantly improved in comparison with the polymerized complex method, and the present catalytic system was applicable to the oxidation of various substrates.

K–Al-based mixed oxides as high-capacity carbon dioxide adsorbents

K–Al-based mixed oxides (KAl6O9.5) with mullite structures were synthesized as CO2 adsorption materials using a polymerized complex method. Al3+ sites in the octahedral AlO6 units of K–Al-based mixed oxides were substituted with various metal ions with +2 or +3 valence states to enhance basicity. Among these samples, the Fe-introduced sample (KAl5.5Fe0.5O9.5) showed 130 times higher CO2 adsorption capacity than that of Li4SiO4. Raman spectra of these samples indicated that large distortions of the AlO6 unit were observed only for the Fe-introduced sample. Local polarization caused by such distortions could induce increased basicity of this sample.

Dopant Concentration induced optical changes in Ba1−xEuxMoO4: A green and facile approach towards tunable photoluminescent material

Ba1−xEuxMoO4 phosphors were synthesized by complex polymerization method. The prepared phosphor material was extensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetry (TG) and differential thermal analysis (DTA). The introduction of europium upto 2mol% doesn’t change the crystal structure. The influence of Eu concentration on the luminescent properties of phosphors was analyzed. It was seen that, under UV irradiation, the pure BaMoO4 sample shows multicolor emission. The blue and green emission was attributed to 1T2 → 1A1 transition within MoO42− moeity (shallow defects), whereas the red- orange emission to the defect MoO3 group (deep defects). The intensity of magnetic dipole transition (MDT) was found to be lower than that of electric dipole transition (EDT) which indicates the low -⁠ symmetry acentric environment of Eu3+ ions. Based on Stark splitting, the actual site symmetry of Eu3+ in BaMoO4 was clarified as C6v; reduced from actual S4 for Ba2+ ion in BaMoO4. The decay curve shows two different lifetime value 11.2 µs (τ1) (host contribution) and 693 µs (τ2) (europium sitting at Ba2+ site) with magnitudes 14% and 86% respectively. The value of host dopant energy transfer efficiency calculated under forbidden f-f transition excitation was found to be lower at 12.6% as compared to 76% in case of excitation by allowed charge transfer band. To find out the concentration quenching mechanism, the critical energy-transfer distance for the Eu3+ ions was evaluated to be 33.81Å, which was found to be greater than 10Å and signify electric multipolar interactions as the only mode of energy transfer The intensity of peaks corresponds to EDT was found to be high in comparison to the peak due to MDT in all the Eu- doped samples: indicating the asymmetric local site symmetry around Eu3+. This is also reflected in the JO (Judo Ofelt) parameter trend; at all concentrations, Ω2 value is greater than Ω4 indicating the high covalency of the Eu3+ ligand bonding and asymmetric environment around europium ion in BaMoO4, which is highly probable because it occupies the asymmetric Ba2+ position.

Efficient photocatalytic hydrogen production over La/Rh co-doped Ruddlesden-Popper compound Sr2TiO4

Layered semiconductor compounds often exhibit intriguing properties for photocatalytic water splitting, probably correlated with their peculiar crystal structures that facilitate charge separations. In this work, we perform an investigation on the layered Ruddlesden-Popper compound Sr2TiO4 and its La/Rh co-doped counterparts for photocatalytic hydrogen production from water. Their crystal structures, optical absorption and other physicochemical properties have been systematically explored. Our results suggest that La/Rh can be successfully incorporated into Sr2TiO4 with layered crystal structure maintained. The use of polymerized-complex method for sample synthesis significantly reduces the calcination temperature as low as 900°C. La/Rh serves as efficient dopants for extending the light absorbance of Sr2TiO4 as far as 550nm. Photocatalytic hydrogen productions are also considerably improved after La/Rh co-doping under both full range (λ≥250nm) and visible light irradiation (λ≥420nm). An optimal doping level is reached at 3% (Sr1.97La0.03Ti0.97Rh0.03O4) which gives the highest average hydrogen production rate ∼100μmol/h and ∼40μmol/h under full range (λ≥250nm) and visible light irradiation (λ≥420nm), corresponding to apparent quantum efficiency ∼1.27% and ∼1.18%, respectively. Photoelectrochemical analysis reveals that charge separation and electron lifetime strongly depends on the level of La/Rh co-doping. Mott-Schottky analysis and theoretical calculations indicate that the improved light absorption of La/Rh co-doped Sr2TiO4 stems from the formation of new valence band with Rh 4d character which uplifts the valence band edge of Sr2TiO4.

Effect of polymerization/complexation agents molar ratio on structure and catalytic activity of La0.7Ba0.3Co0.3Ni0.7O3 nanocatalyst in low-temperature CO oxidation

Nano-sized perovskite-type oxides of La0.7Ba0.3CoxNi1-xO3 (LBCN) catalysts with x = 0.3, 0.5 and 0.7 were synthesized by polymerized complex method based on the Pechini-type reaction route wherein ethylene glycol and citric acid were used as polymerization/complexation agents. The effects of different ethylene glycol/citric acid molar ratio in the sol–gel process on the structure and catalytic activity of the synthesized La0.7Ba0.3Co0.3Ni0.7O3, which displayed superior catalytic performance toward CO oxidation, were examined. The structure, component band identification, morphology, reducibility, and specific surface area of the prepared LBCNs were investigated with X-ray diffraction, FT-IR, SEM, H2-TPR, and BET, respectively. According to H2-TPR results, the shift of reduction peaks of the LBCN nanocatalysts to the lower temperatures indicated that the reduction of Co3+ to Co2+ can be carried out at the lower temperatures, resulting in the improvement of the redox capacity of LBCNs. The results confirmed superiority of the prepared LBCNs over LaCoO3 especially for EG/CA = 5 for the CO oxidation, resulting in achievement of 90% CO oxidation at 180 °C.

The crystalline and magnetic properties of Zn doped strontium Z-type hexaferrite synthesized by polymerizable complex method

Polycrystalline samples of Sr3Co2-xZnxFe24O41 (x = 0.0, 0.5, 1.0, 1.5, 2.0) were synthesized by a polymerizable complex method. The crystallographic, and magnetic properties of samples were investigated using x-ray diffractometer (XRD), vibrating sample magnetometer (VSM), and Mössbauer spectroscopy. The crystal structures of all samples were determined to be hexagonal with the space group P63/mmc. The hysteresis curves under 10 kOe at 295 K showed that all samples were not saturated due to the high planar anisotropy of Sr ions. In addition, the coercivity (Hc) of samples decreased with increasing Zn ion contents. Mössbauer spectra of all samples were obtained at 295 K, and least-squares fitted below TC as six distinguishable sextets (4fIV, 4fIV*, 12kVI*, 4fVI*+ 4eIV, 12kVI, and 2dV + 2aVI + 4fVI + 4eVI).

Effect of Additive Size on the Densification and Thermal Conductivity of AlN Ceramics with MgO–CaO–Al2O3–SiO2 Additives

In this study, we investigate the effect of additive size on the densification and thermal conductivity of AlN ceramics with MgO–CaO–Al₂O₃–SiO₂ (MCAS) additives. Micro-sized MCAS powder prepared via melting and nano-sized MCAS powder synthesized via the polymeric complex method are used as sintering additives. We analyze the densification behavior of AlN added with 5 wt.% of MCAS by dilatometry as well as by isothermal sintering in the temperature range of 1300 ~ 1700℃. AlN exhibits higher sinterability with nano-MCAS than with micro-MCAS, and both specimens approach their maximum densities when sintered at 1600℃ for 4 h. The thermal conductivities of AlN with 5 wt% of nano- and micro-MCAS additives sintered at 1600℃ are 82.6 and 32.0 W/mK, respectively. We find that nano-MCAS is more effective in sintering of AlN ceramics at lower temperatures, and thus for enhancing their thermal conductivities.

Charge transfer-type fluorescence of Ti-doped Ca14Al10Zn6O35

The calcium aluminum zincates Ca14(Al1-2xTixZnx)10Zn6O35, in which Al3+ sites in the host material Ca14Al10Zn6O35 are simultaneously substituted by Ti4+ and Zn2+, were synthesized by a polymerized complex method. Al3+ ions could be replaced up to an x value of 0.1. The host material does not exhibit fluorescence, while the cation-substituted samples show an emission band centered at 383nm under excitation by UV light at 243nm. The emission intensity increases with x up to 0.1 and then gradually decreases as x is further increased. The emission wavelength also becomes longer with increasing temperature. Based on the properties of other Ti4+-containing fluorescent materials, the emission of Ca14(Al1-2xTixZnx)10Zn6O35 is attributed to charge transfer-type fluorescence resulting from [TiO6] octahedra.

Characterization and photoluminescence properties of ultrafine copper molybdate (α-CuMoO4) powders prepared via a combustion-like process

We report a simple method for preparing copper(II) molybdate (CuMoO4) powders via a combustion-like process. A gel was first prepared by the polymerizable complex method, where citric acid was used as a complexing and polymerizing agent and nitric acid was used as an oxidizing agent. The thermal decomposition behavior of the (CuMo)-precursor gel was studied by thermogravimetry–differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). We observed that the crystallization of CuMoO4 powder was completed at 450°C. The obtained homogeneous powder was composed of grains with sizes in the range from 150 to 500 nm and exhibited a specific surface area of approximately 5 m2/g. The average grain size increased with increasing annealing temperature. The as-prepared CuMoO4 crystals showed a strong green photoluminescence emission at room temperature under excitation at 290 nm, which we mainly interpreted on the basis of the Jahn-Teller effect on [MoO 4 2− ] complex anions. We also observed that the photoluminescence intensity increased with increasing crystallite size.

고상반응법과 착체중합법으로 합성된 SrAl2O4: Eu2+, Dy3+축광성 형광체의 특성 및 열적 안정성 평가

고상반응법과 착체중합법으로 합성된 SrAl₂O₄: Eu²⁺, Dy³⁺축광성 형광체의 특성 및 열적 안정성 평가

Synthesis and Characteristics of SrAl2O4: Eu2+, Dy3+ Long Afterglow Phosphors by Polymerized Complex Method

SrAl2O4: Eu2+ and Dy3+ phosphorescent phosphors were synthesized using the polymerized complex method. Generally, phosphorescent phosphors synthesized by conventional solid state reaction show a micro-sized particle diameter; thus, this process is restricted to applications such as phosphorescent ink and paint. However, it is possible to synthesize homogeneous multi-component powders with fine particle diameter by wet process such as the polymerized complex method. The characteristics of SrAl2O4: Eu2+ and Dy3+ powders prepared by polymerized complex method with one and two step calcination processes were comparatively analyzed. Temperatures of organic material removal and crystallization were observed through TG-DTA analysis. The crystalline phase and crystallite size of the SrAl2O4: Eu2+ and Dy3+ phosphorescent phosphors were analyzed by XRD. Microstructures and afterglow characteristics of the SrAl2O4: Eu2+ and Dy3+ phosphors were measured by SEM and spectrofluorometry, respectively.

Synthesis of MgO-CaO-Al2O3-SiO2 nanocomposite powder by polymeric complex method as a novel sintering additive of AlN ceramics

A MgO-CaO-Al2O3-SiO2 (MCAS) nanocomposite powder with a particle size of 50 nm and a specific surface area of 40.6 m2/g was successfully synthesized via heat-treatment of polymeric precursors containing Mg, Ca, Al and Si in air at 700 °C for 5 h. It was characterized as a novel sintering additive for the densification AlN ceramics at a low temperature below 1600 °C. It was found that the nanosized MCAS powder was suitable for the densification of AlN ceramics. In particular, full densification could be achieved when only 1.0 wt% MCAS additive-doped AlN powder compact was sintered for 1 h at 1600 °C, and a thermal conductivity of 84 W/m·K was attained.

Synthesis of Deep-Red La2MgGeO6:Mn4+ Phosphors for Indoor Plant Cultivation By Polymerized Complex Method

Phosphor converted white light-emitting diodes (LEDs) has been extensively practiced in lamps and displays as a next generation white light source, because it offer more benefits, including high luminescence efficiency, a long lifetime, compactness, and low environmental load. Recently, in the area of agricultural research, the LEDs have been actively studied as the light source for “indoor plant cultivation” [1]. Indoor plant cultivation is to grow plants within a controlled environment, meaning filtered air, steady temperature, and special growth media. The ideal environment permits stable supply of vegetables without the influence from the outside. The stable supply can hold the price increase, resulting from short supply, due to drought, loss caused by cold weather, and other disasters. Therefore, indoor cultivate is expected as a solution approach to the global food problem. Artificial light used in indoor plant cultivation is one of important factors. The growth of plant tissues requires three emitting colors: (1) blue light around 450 nm affecting the growth of chlorophyll, flower-bud formation, leaf morphogenesis, and phototropism, (2) red light around 660 nm helping budbreak and internodal elongation, and (3) far-red light around 730 nm promoting photosynthesis. Among them, far-red light is especially significant for preparation of higher-value vegetables, because it prevents aggravation of eating quality and the bitterness caused by the excessive growth of vegetables [2]. Convert-type white LEDs built up with blue LED emitting around of 450 nm and yellow Y3Al5O12:Ce3+ (YAG:Ce3+) have been studied as a prospective light source used in indoor plant cultivation, because of their suitable emission for the culture of plants. Currently, the combination of this the LED and the blue light excitable red LED emitting round 660 nm has been reported as a candidate for the next artificial light source redeemed red light [3]. However, the intensity of its far-red emission is insufficient. Novel blue light excitable deeper-red phosphors, therefore, are required in order to develop an artificial light source in indoor plant cultivation, achieving effective growth of plants and preparation of higher-value vegetables. Mn4+ doped phosphors are excited by blue light and exhibit red emission corresponding to the 4A2 → 4T2 and 2E → 4A2 transitions of Mn4+. La2MgGeO6:Mn4+ [4] is a good candidate for a deep-red phosphor of an artificial light source in indoor plant cultivation, because of their suitable excitation and emission spectra. In addition, it is obtained by easy synthetic condition compared to other Mn4+ doped phosphors such as CaAl12O9:Mn4+ [5], 3.5MgO・0.5MgF2・GeO2:Mn4+ [6]. La2MgGeO6:Mn4+ phosphors are usually synthesized by a conventional solid state reaction method. The method has two drawbacks: the high temperature (1350℃) needed in the heating condition and the concentration quenching, owing to Mn4+ions inhomogeneously distributed. In this study, overcome the drawbacks, we synthesized La2MgGeO6:Mn4+ phosphors by polymerized complex method. Polymerized complex method exploits polymerization between ethylene glycol and citric acid. They form the soluble metal-citric acid complexes. The complexes are immobilized in a rigid polyester network almost in the molecular level, reflecting the original solution [7]. Owing to this mechanism, this method has the advantage; the each ion is homogeneously distributed. Therefore, it is expected to be obtained the La2MgGeO6:Mn4+ samples homogeneously distributed Mn4+, resulting in high efficiency, at low temperature [8]. The luminescence properties of synthesized samples by polymerized complex method are compared with that prepared by the conventional solid state reaction method. [1] N. Yeh and J.-P. Chung, Renew. Sustain. Energy Rev., 2009, 13, 2175. [2] Y. Mori amd M. Takatsuji, Shokubutsu Kojo no tachiagekata・susumekata [How to establish/ forward the LED plant factory] (in japanese), (Nikkan kogyo shinbun, Tokyo), 2013. [3] M. Takatsuji and Y. Mori, Shokubutsu Kojo [the LED plant factory] (in japanese), (Nikkan Kogyo Shinbun, Tokyo), 2011. [4] K. Seki, K. Uematsu, T. Ishigaki, K. Toda, and M, Sato, J. Ceram. Process. Res., 2011, 12, s286. [5] T. Murata, T. Tanoue, M. Iwasaki, K. Morinaga and, T. Hase, J. Lumin., 2005, 114, 207. [6] W. Low, Phy. Rev., 1957, 105, 793. [7] M. Kakihana, J. Sol-Gel Sci. Tech., 1996, 6, 7. [8] T. Isobe, Development and Applications of Nanophosphors (in japanese), (CMC pub., Popular Ed.), 2012.

Lithium-Rich Layered Cathode Materials Containing 3d and 4d Transition Metals for Lithium Ion Battery

Layered rock salt type structure such as LiCoO2 and Li(Mn,Co,Ni)O2 have been used as the cathode materials for lithium ion battery. However, the practical capacity is not enough to require the future demand for the large-scaled energy devices such as electric vehicles or electricity storage systems. The high capacity cathode materials should be developed for the next generation battery system. Layered lithium-rich oxides (xLi2MnO3-(1-x)Li(Mn,Co,Ni)O2) are one of promising candidates and the many researchers have studied them [1-4]. For the practical applications, the irreversible reaction in the initial charge-discharge, the capacity fade and the voltage decrease should be addressed. Recently, the lithium-rich compounds containing 4d transition metals were reported as the interesting cathode materials [5]. In this study, layered lithium-rich compounds containing 3d and 4d transition metals were synthesized and the reaction mechanism was investigated. These knowledges will be useful to develop the next-generation cathode materials. The cathode materials were synthesized by the polymerized complex method. Metal sources were dissolved into nitric acid and citric acid and ethylene glycol were added into this solution with stirring and heated at 200 °C. The obtained polymer was calcined at 400°C for 3 hours. The precursor was pressed into pellets (10 mm diameter) and heated at 850°C for 48 hours. The obtained powders were characterized by X-ray diffraction and scanning electron microscopy. For the charge-discharge measurements, the prepared powder, acetylene black and polyvinylidene difluoride binder were mixed at a weight ratio of 8:1:1 with 1-methyl-2-pyrrolidone solvent. The slurry was coated on the Al foil and dried in a vacuum oven at 80°C. The electrodes were roll-pressed and used as the working electrode. Li foil was used as the counter electrode material and 1 mol/L LiPF6 in a 3:7 volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) was used as the electrolyte. The two-electrode cells were assembled in an argon-filled glove box. X-ray diffraction study showed the prepared samples exhibit the layered rock salt structure without distinct impurities. Scanning electron microscopy showed the particle size of the powder was sub-micrometer. The charge-discharge capacity of this material was about 200 mAh/g. The charge-discharge profile represented a gradual slope and low polarization compared with the case of xLi2MnO3-(1-x)Li(Mn,Co,Ni)O2. Moreover, the irreversible reaction at the high potential caused by oxygen evolution did not occur in the first cycle and showed good cycle performance. This result suggested that lithium-rich layered oxides containing 3d and 4d transition metals have one of promising cathode materials. We will discuss the reaction mechanism of this system in the presentation. [1] M.M. Thackeray, S.-H. Kang, C.S. Johnson, J.T. Vaughey, R. Benedek, S.A. Hackney, J. Mater. Chem., 17 (2007) 3112. [2] T.A. Arunkumar, Y. Wu, A. Manthiram, Chem. Mater., 19 (2007) 3067. [3] F. Mantia, F. Rosciano, N. Tran, P. Novák, J. Electrochem. Soc., 156 (2009) A823. [4] N. Yabuuchi, K. Yoshii, S. Myung, I. Nakai, S. Komaba, J. Am. Chem. Soc., 133 (2011) 4404. [5] M. Sathiya, G. Rousse, K. Ramesha, C. P. Laisa, H. Vezin, M. T. Sougrati, M. L. Doublet, D. Foix, D. Gonbeau, W. Walker, A. S. Prakash, M. Ben Hassine, L. DuPont, J. M. Tarascon, Nat. Mater., 12 (2013) 827.

ChemInform Abstract: The Structure Feature of Layered M1/3TiNbO5 (M: Fe, Ce) and Their Photocatalytic Oxidization Performance for Ethyl Mercaptan.

AbstractLayered photocatalytic M1/3TiNbO5 (M: Fe, Ce) is prepared by ion‐exchange of KTiNbO5 with 2 M M(NO3)3 (96 h).

Variations in the morphotropic phase boundary with Bi deficiency on Ba-substituted sodium bismuth titanate

We successfully demonstrated that a slight Bi deficiency causes the rhombohedral-tetragonal morphotropic phase boundary (MPB) to shift to the considerably lower Ba content in a (Na0.5Bi0.5)1−xBaxTiO3 (Ba-substituted NBT) system. Rietveld analysis revealed that the composition yielding the MPB was located at x = 0.10 when using the polymerizable complex method to prevent evaporation of sodium and bismuth and at x = 0.068 in samples of (Na0.5Bi0.5−z)1−xBaxTiO3−δ with a Bi deficiency of z = 0.03.