Hydroxide Co-precipitation Route Research Articles

Impact of the atmosphere on the sintering capability and chemical durability of Nd-doped UO2+x mixed oxides

In this study, the influence of the working atmosphere on the sinterability and chemical durability of Nd-doped UO2 mixed oxides was investigated. To this end, the starting powder was first prepared by a hydroxide co-precipitation route, resulting in a nano-sized granulometry combined with a high specific surface area. The powders were then converted to oxides by heating and sintered in pellet form at 1600°C under an argon or reducing (Ar-4 %H2) atmosphere. The use of argon or reducing atmosphere resulted in very different densification pathways and final microstructures. The reducing sintering atmosphere hindered the uranium (IV) oxidation that could occur at high temperature, leading to the formation of U3O8, as was the case when working under argon atmosphere. Regarding the microstructure of the sintered pellets, the use of an argon sintering atmosphere resulted in an average grain size ten times larger than that of a reducing sintering atmosphere, while macroscopic properties such as relative density, porosity and homogeneity of cation distribution at the pellet scale remained the same. Nevertheless, a slight local enrichment of Nd at the grain boundaries was observed for the pellet sintered under Ar-4 %H2. In a second step, the study of the chemical durability of these sintered samples showed a significant influence of the sintering atmosphere on the dissolution kinetics and mechanism. These differences could be related to the microstructural properties of the pellets, i.e. the average grain size and the occurrence of grain boundaries. The cation distribution in the pellets could also influence their chemical durability, such as local Nd enrichment, the formation of defects in the oxygen sublattice and the presence of a different fraction of U(V) depending on the sintering atmosphere, as shown by HERFD-XANES measurements. The use of reducing or argon sintering atmospheres could even direct the charge compensation mechanisms that occur into the solid, thereby simultaneously affecting the sinterability and chemical durability of the samples.

Understanding the solid/liquid interface evolution during the dissolution of Nd-doped UO2 by macro-/microscopic dual approach

The chemical durability of Nd-doped UO2 samples was studied using an innovative macro-/microscopic dual approach method. The starting precursor was first prepared by a hydroxide co-precipitation route leading to a nano-sized powder associated to high specific surface area. The powder was then converted into U0.8Nd0.2O2±y solid solution by calcination. After shaping of the oxide powder into the pellet form through uniaxial pressing at 500 MPa, the pellets were sintered at 1600 °C under inert (Ar) or reducing (Ar-4%H2) atmosphere. At the macroscopic scale, multiparametric dissolution tests were carried out under static conditions in 2 mol.L−1 HNO3 at 60 °C. Simultaneously, an operando monitoring of the solid/liquid interface evolution during dissolution was also performed by ESEM at the microscopic scale, in order to follow the consequences of the dissolution on the ceramics microstructure. This dual approach was validated by comparing the calculated normalized dissolution rates obtained for each series of experiments. Changing the sintering atmosphere did not appear to significantly affect the dissolution kinetics of Nd-doped UO2 samples at the macroscopic scale whereas notorious differences in the dissolution mechanisms have been highlighted at the microscopic scale by ESEM monitoring solid/liquid interface.

Synthesis and electrochemical properties of P2–Na2/3[Ni1/3Mn2/3]O2 microspheres as cathode materials for sodium-ion batteries

P2–Na2/3 [Ni1/3Mn2/3]O2 microspheres with well-distributed particle size and high tapping density have been successfully prepared via a hydroxide co-precipitation route associated with the solid-state reaction. The as-prepared P2–Na2/3 [Ni1/3Mn2/3]O2 sample has a high tapping density of 2.23 g cm−3 and hexagonal morphology indexed to P63/mmc space group. At the same time, it consists of monodisperse microspheres with a diameter of 5–8 μm, which are closely assembled by many plate-like primary nanoparticles. As cathode material for sodium-ion batteries (abbreviated as SIBs), it exhibits a high initial capacity of 87.8 mAh g−1 at 0.1 C in the voltage window of 2.3–4.1 V and demonstrates excellent capacity retention of 97.5% after 100 cycles. Therefore, P2–Na2/3 [Ni1/3Mn2/3]O2 microspheres will be a hopeful cathode material for the application of sodium-ion batteries.

Structural, dielectric and magnetoelectric properties of (BSPT–LSMO) composites

The paper discuses mainly P-E and M-H hysteresis loops and magnetoelectric effect in Ba0.8−xSrxPb0.2TiO3 (BSPTx)–La0.7Sr0.3MnO3 (LSMO) composites. BSPTx powder is synthesized using solid state reaction method while, LSMO is synthesized using hydroxide co-precipitation route. The (BSPTx–LSMO) composites are prepared by mixing the respective powder in their weight proportion and sintering at 1100 °C. The resulting composites are investigated for crystal structure, microstructure, dielectric properties and magnetoelectric coupling. The results are understood employing qualitative approach.

Dielectric and magnetodielectric properties of LSMO-BCZT composites

The paper reports the synthesis of Ba0.95Ca0.05Ti0.90Zr0.10O3 (BCZT) composition via ceramic route of synthesis to result into the BCZT composite. The La0.67Sr0.33MnO3 (LSMO) is synthesized using hydroxide co-precipitation route Further, the magnetodielectric (MD) composites of Ba0.95Ca0.05Ti0.90Zr0.10O3(BCZT) are formed by addition of LSMO at y = 0.10, 0.15 and 0.20. The parent BCZT composition is analyzed for its dielectric properties. The composites LSMO-BCZT (LBCZT) are investigated for the variation of dielectric constant and impedance spectra as a function of applied magnetic field for the frequency between 20 Hz and 1 MHz. The observations on MD effect show that the dielectric constant possesses contributions due to magnetic field dependant interfacial polarization and variations due to the induced stress.

Multiferroic properties of SBN–LSMO, SBN–NZCFO and SBN–LSMO–NZCFO particulate composites

Recent studies on nanocrystalline magnetodielectric (MD) composites have shown interesting results. Further, the Sr0.5Ba0.5Nb2O6 (0.5SBN) has proved to be a promising lead free ferroelectric phase to form the magnetoelectric (ME) composites. However, no detailed report on the investigations of MD properties of these composites is available in the literature. Therefore, the present paper reports synthesis and characterization of Sr0.5Ba0.5Nb2O6 (0.5SBN) based ME and MD composites. The ferromagnetic phases La0.67Sr0.33MnO3 (0.33LSMO) and Ni0.85Zn0.1Co0.05Fe2O4 (0.1NZCFO) are so synthesized that both the compositions possess crystallites of nearly 80 nm. 0.5SBN is synthesized using conventional ceramic sintering process, while 0.33LSMO and 0.1NZCFO are synthesized via hydroxide co-precipitation route followed by annealing at higher temperatures. The crystal structure is determined to confirm correct phases of individual compositions. The composites are investigated for the crystal structure, microstructure, dielectric properties, ME coefficients and MD properties. Further, the magnetoelectric coefficient α is sufficiently large. Here, the magnetodielectric properties show presence of stress induced and interfacial polarization induced contributions to the magnetocapacitance (Mc).

Magnetoelectric and magnetodielectric properties of LSMO–(BCT–BZT) composites

The present paper reports magnetoelectric and magnetodielectric properties of La0.67Sr0.33MnO3 and (Ba0.7Ca0.3TiO3)–(BaZr0.2Ti0.8O3) composites. y(La0.67Sr0.33MnO3) + (1 − y)[x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] particulate composites are prepared for x = 0.40, 0.45, and 0.50 and for y = 0.1 and 0.175. Ferroelectric compositions [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] are synthesized via ceramic route, while La0.67Sr0.33MnO3 is synthesized via hydroxide co-precipitation route. Composites of La0.67Sr0.33MnO3 and (Ba0.7Ca0.3TiO3)–(BaZr0.2Ti0.8O3) are synthesized using ceramic method. The crystal structures of La0.67Sr0.33MnO3, [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)], and composites are investigated using X-ray diffractograms, while microstructures are investigated using scanning electron microscope. The dielectric properties of [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] are determined as a function of temperature between 30 and 150 °C and at frequencies 1, 10, 100 kHz, and 1 MHz. The investigations on P–E hysteresis loops of [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] show useful values of maximum polarization (Pmax) and remanent polarization (Pr). Dielectric study on composites is carried out as a function of frequencies between 1 kHz and 1 MHz and for magnetic field between 0 and 6 KOe. The linear magnetoelectric coefficient “α” and quadratic magnetoelectric coefficient “β” are measured with the help of custom-designed setup. The results on magnetoelectric and magnetodielectric properties of composites are interesting.

Synthesis of nanosized LiNi0.7Mn0.2Co0.1O2 cathode material for lithium ion batteries by combination method of forced hydrolytic and hydroxide coprecipitation

A uniform LiNi0.7Mn0.2Co0.1O2 cathode material was synthesised with 0.7 Ni(OH)2–0.3(Mn2/3Co1/3)(OH)2 as precursors prepared using forced hydrolytic route and hydroxide coprecipitation route. The Ni(OH)2 precipitation was first obtained by forced hydrolytic method and then the (Mn2/3Co1/3)(OH)2 coprecipitation was prepared in the suspended solution. The crystal structure and morphology of LiNi0.7Mn0.2Co0.1O2 were characterised by X-ray diffraction and scanning electron microscopy techniques. Spherical-like single phase LiNi0.7Mn0.2Co0.1O2 was synthesised at 750°C for 20 h and delivered excellent electrochemical performance. The high initial discharge capacity was 147.62 mA h g−1 in the potential range of 2.8–4.2 V and 192.89 mA h g−1 in the potential range of 2.8–4.6 V. The reversible capacity after 50 cycles at 0.2 C ratio was 139.8 mA h g−1 at the cutoff potential of 4.2 V and 146.9 mA h g−1 at the cutoff potential of 4.6 V.

Na-doped Ni-rich LiNi0.5Co0.2Mn0.3O2 cathode material with both high rate capability and high tap density for lithium ion batteries.

Na-doped Ni-rich LiNi0.5Co0.2Mn0.3O2 cathode material, Li0.97Na0.03Ni0.5Co0.2Mn0.3O2, is synthesized by a hydroxide co-precipitation route. The structural characterization reveals that the substitution of Na for Li results in a more ordered α-NaFeO2 structure, enlarges Li layer spacing, and reduces the degree of cation mixing. The Li0.97Na0.03Ni0.5Co0.2Mn0.3O2 material has a high tap density of 2.17 g cm(-3) that meets the commercial requirement in lithium ion batteries (LIBs). The galvanostatic charge/discharge results show that the electrochemical performance of the Li0.97Na0.03Ni0.5Co0.2Mn0.3O2 is significantly improved. At 0.2, 1, 10, 30 and 50 C, the specific capacities of the Li0.97Na0.03Ni0.5Co0.2Mn0.3O2 are 228.43, 163.12, 121.43, 95.56 and 60.09 mA h g(-1), respectively, which are superior to those of the undoped LiNi0.5Co0.2Mn0.3O2 due to the enlargement of Li layer spacing, the decreased degree of cation mixing, and the rapid diffusion of Li-ion in the bulk lattice after the substitution of Na for Li. Therefore, the Na-doped Ni-rich LiNi0.5Co0.2Mn0.3O2 material is a promising cathode candidate for the next generation of LIBs.

Magnetoelectric and magnetodielectric effect in BST–LSMO ferromagnetic/ferroelectric composites

Ba1−xSrxTiO3 (BST) for x = 0.20, 0.25 and 0.30 and La0.67Sr0.33MnO3 (LSMO) are synthesized using hydroxide co-precipitation route to lead to nanocrystalline particles of BST and LSMO respectively. Further the magnetoelectric (ME) and magnetodielectric (MD) composites of BST0.20, BST0.25 and BST0.30 are formed by addition of the LSMO at y = 0.1 and y = 0.2. The parent BST compositions are studied for its dielectric properties as a function of temperature and frequency up to 1 MHz. The AC conductivity of LSMO–BST (LBST) is studied and it confirms the conduction to be due to small polarons. The paper also presents ME and MD properties of LBST composites. The observation on MD properties show that the dielectric constant possesses contribution due to magnetic field dependant interfacial polarization and variation due to the stress induced because of the applied magnetic field. Further from the ME study, the maximum value of magnetoelectric coefficient is 15.51 mV/Oe/cm is observed for LBST composites.

Dielectric, magnetoelectric and magnetodielectric properties in CMFO-SBN composites

The paper reports synthesis of Sr0.5Ba0.5Nb2O6 (SBN) and Co1.2−xMnxFe1.8O4 (CMFO) via ceramic and hydroxide co-precipitation routes respectively. The nanopowders of SBN-CMFO0.1 (MSBN0.1) and SBN-CMFO0.3 (MSBN0.3) are compacted to form the desired magnetoelectric (ME)/magnetodielectric (MD) composites. The Bi2O3 is used as a sintering aid. The Bi2O3 at three weight percent is observed to cause agglomeration of SBN and CMFO particles and improve the magneto-mechanical coupling. The composites are investigated for their ferroelectric, ferromagnetic, dielectric, magnetoelectric (ME) and magnetodielectric (MD) properties. The results on the magnetocapacitance (Mc) are observed interesting and could be correctly understood in terms of the stress induced variation in the dielectric constant. The MC is observed to remain fairly constant between 10 to 500kHz and possess a useful magnitude of Mc nearly 4%.

Magnetoelectric and magnetodielectric effect in Ba1−xSrxTiO3 and Co0.9Ni0.1Fe2−xMnxO4 composites

Ba1−xSrxTiO3 (BST) is a ferroelectric material known to possess ferroelectric transition temperature Tc in the vicinity of room temperature ∼30 °C for x = 0.3. As the BST with x in the vicinity of 0.3 is elastically soft at 30 °C, the compositions with x = 0.2, 0.25 and 0.3 are chosen to investigate their possible magnetoelectric (ME) and magnetodielectric (MD) applications. The (CoNi) FeMn2O4 (CNFMO) is selected to be a piezo-magnetic phase. Here hydroxide co-precipitation route is adopted so as to synthesize BST and CNFMO of nearly 100 nm crystallite size. Starting with the BST and CNFMO powders, the composites yCNBST = yCNFMO + (1 − y) BST are synthesized for y = 0.3 and 0.4. The parent compositions of BST as well as the CNFMO are characterized for dielectric and magnetic properties to confirm the formation of the desire ferroelectric and magnetostrictive phases. The composites are investigated for the crystal structure, dielectric, magnetoelectric and magnetodielectric properties. The results show that the composite Ba0.75Sr0.25TiO3–Co0.9Ni0.1Fe1.7Mn0.3O4 exhibit excellent ME and MD properties simultaneously. The results on the ME and MD properties are understood in terms of the stress induced variations in polarization and dielectric constant ɛ respectively.

Investigations on nanocrystalline BST-LSMO magnetodielectric composites

The paper reports the synthesis of Ba1−xSrxTiO3 (BST) for x = 0.20, 0.25, and 0.30 via hydroxide co-precipitation route to result into the BST nanoparticles of size nearly 50 nm. The La0.67Sr0.33MnO3 (LSMO) is also synthesized using co-precipitation route to achieve nanocrystaline particles. Further, the magnetodielectric (MD) composites of BST0.20, BST0.25, and BST0.30 are formed by addition of the LSMO at y = 0.1 and 0.2. The parent BST compositions are analysed for its dielectric properties. The composite LSMO-BST (LBST) is investigated for the variation of dielectric constant and impedance spectra as a function of applied magnetic field for the frequency between 500 Hz to 1 MHz. The observations on MD effect show that the dielectric constant possesses contributions due to magnetic field dependant interfacial polarization and variations due to the induced stress.

Magnetoelectric and magnetodielectric properties of SBN–CMFO nanocomposites

The paper reports synthesis of nanoparticles of Sr0.5Ba0.5Nb2O6 (SBN) and Co1.2−xMnxFe1.8O4 (CMFO) via ceramic and hydroxide co-precipitation routes, respectively. The nanopowders of SBN–CMFO0.1 (MSBN0.1) and SBN–CMFO0.3 (MSBN0.3) are compacted together to form the desired magnetoelectric/magnetodielectric (ME/MD) composites. The Bi2O3 is used as a sintering aid. The Bi2O3 at three weight percent is observed to cause agglomeration of SBN and CMFO particles and improve the magnetomechanical coupling. The paper reports synthesis, structural and morphological studies on the MSBN composites. The composites are investigated for their dielectric, ME and MD properties. The results on the magnetocapacitance (MC) are observed interesting and could be correctly understood in terms of the stress-induced variation in the dielectric constant. The MC is observed to remain fairly constant between 10 and 500 kHz and possess a useful magnitude of nearly 4 %.

DIELECTRIC BEHAVIOUR, COMPLEX IMPEDANCE SPECTROSCOPY AND MAGNETOELECTRIC EFFECT IN LSMO-BT COMPOSITES

The paper deals with Dielectric Behaviour, Complex Impedance Spectroscopy and Magnetoelectric effect in La 0.7 Sr 0.3 MnO 3(LSMO) and BaTiO 3 (BT) Composites. The LSMO and BT are synthesized by hydroxide co-precipitation route. The nanocomposites are prepared by two series x LSMO + (1-x) BT + 2 wt % Bi 2 O 3, for x = 0.05, 0.1, 0.15 and 0.2 ……series 1. x LSMO + (1-x) BT + 3 wt % Bi 2 O 3, for x = 0.05, 0.1, 0.15 and 0.2 ……series 2. and sintered at Ts=1000°C and 1080°C. The composites are termed as LSMO - BT . The paper reports the crystal structure, micro-structural analysis, dielectric constant, complex impedance spectroscopy and magnetoelectric properties of LSMO - BT composites. It has been observed that the ε r passes through a broad maximum at T ~ 124° C, which is nearly the ferroelectric transition temperature of BT . Both ε r and ε rmax increases as x increases from 0.05 to 0.2. The ε r ' and ε r '' decreases sharply for all the compositions at low frequencies. This feature is typical of the presence of interfacial polarization. The variation of 4πMs is almost linear with x , the 4πMs increases with x as well as sintering aid. The 4πMs of respective compositions reduce as the sintering temperature is increased. The value of α increases for increase in sintering temperature as well as increase in wt % of the sintering aid. The magnitude of α is in the range as reported earlier for composites based on BT .

Synthesis and Characterization of La0.7Sr0.3MnO3 And Pbzr0.5Ti0.5O3 Nanopowders Using Hydroxide Co-Precipitation Route

Synthesis and Characterization of La0.7Sr0.3MnO3 And Pbzr0.5Ti0.5O3 Nanopowders Using Hydroxide Co-Precipitation Route

Hydroxide Co-Precipitation Route for Synthesis of La0.7Sr0.3MnO3 - BatiO3 Nanocomposites

Hydroxide Co-Precipitation Route for Synthesis of La0.7Sr0.3MnO3 - BatiO3 Nanocomposites

Oxidative Dehydrogenation of Ethylbenzene over Cu1-xCoxFe2O4Catalyst System: Influence of Acid–Base Property

A series of Cu–Co ferrites with the general formula Cu1-xCoxFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1.0) was prepared by a low-temperature hydroxide coprecipitation route. The catalyst systems were characterized by adopting various physicochemical techniques. The acid–base properties were studied in detail, and the catalytic activity as well as the selectivity for oxidative dehydrogenation of ethylbenzene was compared for various compositions. FTIR adsorption of pyridine is carried out to understand the relative acidity of various compositions of the systems. IR studies of spinel surface with adsorbed CO2 and adsorption studies of electron acceptors such as 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro-1-4-benzoquinone and p-dinitrobenzene are carried out to evaluate the nature of basic sites and the strength and distribution of electron donor sites present on the spinel surface. It is found that acidity (basicity) of the Cu1-xCoxFe2O4 spinel system increases (decreases) from x = 0 to 1. A good correlation was found between the activity for this reaction and the surface acid–base properties of the catalysts. Intermediate compositions show better catalytic performance, among which x = 0.50 is superior and demonstrates an intermediate acid–base character. It was observed that dehydrogenation of ethylbenzene to styrene proceeds mainly on an acid–base pair site.

Selective synthesis of 3-picoline via the vapor-phase methylation of pyridine with methanol over Ni1-xCoxFe2O4 (x = 0, 0.2, 0.5, 0.8 and 1.0) type ferrites

A series of Ni–Co ferrites with the general formula Ni1-x Co x Fe2O4 (x = 0, 0.2, 0.5, 0.8 and 1.0) was prepared by a low-temperature hydroxide coprecipitation route. The catalyst systems were characterized by adopting various physico-chemical techniques. Alkylation of pyridine with methanol was carried out in a down-flow vapor-phase reactor. The influence of surface acid–base properties, cation distribution in the spinel lattice and various reaction parameters are discussed. It was observed that the systems possessing x values ≥0.5 are selective for 3-picoline formation, whereas the ones with x values 0 and 0.2 give a mixture of 2- and 3-picolines. Pyridine conversion increased with the progressive substitution of Ni2+ ions by Co2+ ions. Cation distribution in the spinel lattice influences their acidic and basic properties, and these factors have been adequately considered as helpful to evaluate the activity of the systems.

Hydroxide coprecipitation route to the piezoelectric oxide Pb(Zr,Ti)O3(PZT)

A homogeneous and stoichiometric fine powder of the piezoelectric oxide Pb(Zr0.52Ti0.48)O3(PZT) has been prepared by the hydroxide coprecipitation route. By considering the thermodynamic equilibrium constants, the solubility and ionic equilibria relationships for individual metal hydroxides in aqueous media could be theoretically evaluated as a function of solution pH and metal ion concentration. An optimal pH of 9 for the coprecipitation of the ternary Pb-Zr-Ti system as hydroxides was predicted from the solubility diagrams, and the quantitative coprecipitation of metal hydroxides was confirmed experimentally. Pb(Zr0.52Ti0.48)O3 as a single phase was obtained by thermal decomposition of the coprecipitated hydroxide precursor above 500 °C. The calcined powders at various temperatures were characterized by inductively coupled plasma (ICP) studies, thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements.