Solid-state Synthesis Method Research Articles

Phase transformations and changes in the dielectric properties of nanostructured perovskite-like LBZ composites as a result of thermal annealing

The paper presents the results of a study of changes in the phase composition and dielectric properties of perovskite-like composites of the LiBaZrOx type depending on the temperature of the heat treatment. According to the data obtained, the initial samples obtained by the solid-state synthesis method are a three-phase system with the dominance of the orthorhombic phase ZrO2, the average nanoparticle size of which consists of composites, does not exceed 90–110 nm. As a result of thermal annealing, the dependences of phase transformations, as well as the dynamics of structural ordering with the formation of core-shell structures at an annealing temperature of 1000 °C, were established. The reduction of distortions and deformations of the crystal structure as a result of thermal annealing leads to an improvement in ferroelectric properties, as well as a decrease in the Curie temperature characteristic of the maximum dielectric constant. The weak dependence of the change in the dielectric constant with increasing frequency in the temperature range exceeding the Curie temperature indicates the relaxor nature of the properties of composites.

Structural, photo, optical and thermal luminescent properties of beta barium metaborate

Barium borate compounds (BaB4O7 – β-BaB2O4) were produced by different synthesis methods, which include solution assisted solid state synthesis method (SAS), microwave assisted solid state synthesis method (MAS) and high temperature solid state synthesis method (HTS). These different synthesis methods were carried out in air atmosphere (AA) and nitrogen atmosphere (NA). Luminescence emission spectra of barium borate compounds exhibited a broad band around 400 nm (∼310 nm excitation). X- ray induced luminescence measurements have shown a similar emission band, supporting the PL measurements. Photoluminescence decay curve of β-BaB2O4 compound (excited with 365 nm) is well fitted with a double exponential function with lifetimes τ1=3,69 ms and τ2=29,45 ms. At around 365 nm, Quantum Efficiency (QE) of the luminescence emission from β-BaB2B4 was calculated as 8 ± 1 percent. In order to test the possibility of using in radiation dosimetry, Optically Stimulated Luminescence (OSL) properties of β-BaB2O4 were investigated by determining radiation dose response, fading and repeatability of response. The OSL signal intensity was observed to increase linearly with increasing beta dose from 5 Gy to 1000 Gy. Thermoluminescence (TL) glow curve of β-BaB2O4 phosphor consist of broad glow peak with an apparent maximum at around 240 °C; which is also growing with radiation dose. The results presented here are of preliminary in nature and for a better understanding of the luminescence properties of β-BaB2O4 deserves more attention with possible applications as a phosphor and optical and dosimeter material.

Crystal structure and XANES study of Sn-substituted YBa2Cu3O7-y powder prepared by solid-state synthesis method

In this research, the crystal and chemical characterizations of Sn-substituted YBa2Cu3O7-y (YBCO) powder were studied. The experimental powder samples of (Y1-xSnx)Ba2Cu3O7-y (0 ≤ x ≤ 0.2) were prepared using the solid-state synthesis method. The starting precursor powders in appropriate ratios were mixed and calcined at 880 °C for 12 h in a normal atmosphere. The calcined powders were investigated for phase content using the X-ray diffraction technique (XRD). The microstructure of the powders was investigated by scanning electron microscopy (SEM). The chemical composition was carried out by energy-dispersive X-ray analysis (EDX). In addition, the details of the oxidation state of Sn and Cu determined by X-ray absorption near-edge structure (XANES) spectroscopy was also analyzed and discussed in relation to the cationic site substitution and variation in the local structure. It was found that the indexing of the XRD pattern showed Sn-substituted YBCO main peaks, and the impurity peaks of BaSnO3 and BaCuO2 were also found in the pattern. The small solubility of Sn in YBCO matrix was the major factor which induced the formation of the latter secondary phase. SEM images of the particles indicated that they possessed an irregular shape with a particle-size range of 1–3 μm. Sn L3-edge XANES spectra indicated that the average formal valence of Sn was Sn2+/Sn4+. The Cu K-edge spectra helped confirm that the Sn ions could not substitute Cu site in YBCO structure.

Effect of Nb–Sm co-doping on the ionic conductivity of Li7La3Zr2O12 electrolytes

Li-conducting oxide material Li7La3Zr2O12 is a promising solid electrolyte due to its relatively high conductivity. In this work, Li7−x+yLa3Zr2−x−yNbxSmyO12 (0 ≤ x ≤ 0.4, 0 ≤ y ≤ 0.1) was prepared using a solid-state synthesis method, and the effects of Nb–Sm co-doping on the structure, microstructure, and conductivity of Li7La3Zr2O12 were investigated. Results showed that the co-doping of supervalent cation Nb and low-valent cation Sm was able to facilitate the formation of cubic garnet modification. The optimized composition Li6.7La3Zr1.5Nb0.4Sm0.1O12 showed the highest relative density at 94.3%, and reached the highest total conductivity of 1.06 × 10−3 S/cm at 30 °C, with the lowest activation energy of 0.39 eV. Based on SEM and above results, it can be found that the Nb–Sm co-doping can enhance sinterability and increase density, leading to lower impedance and higher conductivity. Although a small amount of impurity phase LaNbO4 was observed in the XRD patterns, its overall influence on ionic conductivity was negligible.

EFFECT OF Gd2O3 DOPING ON DIELECTRIC PROPERTIES OF Ba(Zr0.1Ti0.9)O3 CERAMICS

Using BaCO3, TiO2, ZrO2 and Gd2O3 as the starting materials, the Ba(Zr0.1Ti0.9)O3 ceramics are prepared using solid state synthesis method, and effects of Gd2O3 dopant on microstructure and dielectric properties of Ba(Zr0.1Ti0.9)O3 ceramics are investigated. The results show that the crystal structure for Ba(Zr0.1Ti0.9)O3 ceramics is a single perovskite structure, and the doping of Gd3+ does not generate new phase. With the Gd2O3 concentration increasing, the grain size increases continuously, when the doping amount x ≥ 0.5 mol %, the grain size basically remains unchanged, the grain size is uniform. With the Gd2O3 content increasing, the dielectric constants rose first and then decreased under different sintering conditions of 1280 °C, 1300 °C, 1330 °C, and 1350 °C. When the sintering temperature is 1350 °C and the Gd3+ doping amount is x = 0.5 mol %, the dielectric loss is minimal, the dielectric constant is the highest, and the dielectric performance at room temperature is optimal. Gd2O3 doping has little effect on the movement of the Curie point of BZT ceramics, but the doping of Gd2O3 can increase the peak of the dielectric peak at the Curie point.

Adverse Effect of Europium Doping on Magneto-Optical Properties of Cr2O3

The article describes in detail the effect of doping Europium (Eu) on magnetic and optical properties of Cr2O3. Undoped and Eu (1–5 mol%) doped Cr2O3 samples were synthesized using solid state synthesis method. The structural, magnetic and optical properties of undoped and Europium (Eu) doped chromium oxide powder were studied by X-ray diffractometer (XRD), vibrating sample magnetometer (VSM) and photoluminescence (PL) measurements. The X-ray diffraction pattern confirms the polycrystalline nature of undoped and Europium (Eu) doped chromium oxide powder. The magnetic measurements revealed decline in magnetism with increasing Eu concentration. With increasing Eu concentration, the visible luminescence of Cr2O3 improved. The study highlighted that Eu as a dopant is not suitable for improving the magnetic properties of Cr2O3.

EFFECT OF HOLDING TIME DURING SINTERING ON DIELECTRIC AND PIEZOELECTRIC PROPERTIES OF 0.96KNN-0.04 LiSbO3 CERAMICS

K2CO3, Na2CO3, Li2CO3, Sb2O3 and Nb2O5 were used as the starting materials, the 0.96(Na0.5K0.5)NbO3-0.04LiSbO3 ceramics are prepared using solid state synthesis method, and effects of holding time during sintering on dielectric and piezoelectric properties of 0.96KNN-0.04 LiSbO3 ceramics are investigated. The crystal structure was detected using X-ray diffraction characterization, and the micrographs were observed by field emission scanning electron microscopy. The results show that the crystal structure for 0.96KNN-0.04 LiSbO3 ceramics with different holding time is all perovskite structure, with the extension of holding time, the proportion of the two diffraction peaks decreases gradually, and presents the trend of gradually merging into a single peak. With the extension of the holding time, the relative dielectric constant increases first and then decreases, reaching the maximum value of 1015 at 5 h. With the increase of holding time, the Curie temperature Tc moves to high temperature, Tc rises from 295 oC to 350 oC, at the same time, the dielectric constant at Curie point reaches 4869 when the holding time is 5 h. Afterwards, the piezoelectric constant increases first and then decreases with the increase of holding time, and the holding time is 5 h, d33 = 147 pC/N, reaching the maximum value. So the dielectric and piezoelectric properties of 0.96KNN-0.04 LiSbO3 ceramics are optimized when the holding time is 5 h.

Air stability of tetragonal solid-state electrolyte Li7La3Zr2O12

Solid-state synthesis method used to prepare pure (98%) tetragonal Li7La3Zr2O12 as a material with high lithium ion conductivity. Calcined at 900 °C for 6 h powder material has little amount impurity of La2O3. Energy-dispersive X-ray spectroscopy shows uniform distribution of Zr, La and O at material particles. Then powder put to desiccator with air atmosphere and pressure of 105 Pa for 3 months. Further X-ray diffraction test revealed increasing of impurity amount of La2O3 and formation of La(OH)3 impurity.

Quantitative assessment of degradation, cytocompatibility, and in vivo bone regeneration of silicon-incorporated magnesium phosphate bioceramics

Abstract

Luminescence and color properties of Ho3+ co-activated Sr4Al14O25: Eu2+, Dy3+ phosphors

We report on the photoluminescence properties of Sr4Al14O25:Eu2+,Dy3+ (SAED) phosphors modified by adding Ho3+ in excess and partially substituting Dy3+ with Ho3+ (SAEDHs). Samples were produced using an established solid-state synthesis method known to consistently yield long-persistent afterglow phoshors. Substitutions were performed in stoichiometrically modified host lattices (Al/Sr = 3.2, 3.5, 3.7). Partially substituting Dy3+ with Ho3+ resulted in a remarkable increase in photoluminescence (PL) intensity, Ho3+ co-doping caused a shift in the main emission peaks between 494 and 497 nm and introduced new peaks as well. Important from the security application point of view, the PL intensity was significantly improved under both purple (400 nm) and blue (445 nm) illumination. Color shift of the powders from green to a yellowish and pale pink shade resulted from the Ho3+ addition. Afterglow (AG) properties and thermoluminescence (TL) response decreased non-gradually as Dy3+ was substituted by Ho3+, due to possible charge transfer effects caused by Ho3+. AG and TL properties remained more intact in the presence of Ho3+ when the Al/Sr ratio differed from the ideal 3.5 ratio. Rearrangements of trap energy levels, and energy transfer induced by Ho3+ co-doping were analysed by TL. Dy3+/Ho3+ co-dopants and Al/Sr stoichiometric ratios asymmetrically influenced the trapping/detrapping and energy transfer processes of the SAEDH phosphors. The developed new materials meet the general characteristics of long-persistent phosphors: charging by sunlight, efficient light conversion, chemical stability, all-night afterglow observable by the human eye.

Effect of La3+ Substitution at Bi-Site on Transport Properties of Bi0.3-xLaxPr0.3Ca0.4Mn0.1Cr0.9MnO3

Magnetic and electronic transport properties of Bi0.3-xLaxPr0.3Ca0.4Mn0.1Cr0.9O3 (0≤x≤0.2) manganites have been investigated by measurements of AC-susceptibility, resistivity and magnetoresistance. The samples were prepared using conventional solid-state synthesis method. Magnetic susceptibility versus temperature measurements showed all samples exhibit ferromagnetic to paramagnetic transition with Curie temperature, Tc enhanced from 111 K (x=0) to 174 K (x=0.2). Electrical resistivity measurements of the samples in zero field showed increase of metal-insulator (MI) transition temperature from 58 K(x=0) to 88 K(x=0.2). The increase in both Tc and TMI indicates enhancement of double exchange (DE) interaction involving Mn3+ and Mn4+ ions as a result of weakening of the hybridization effect between Bi3+ 6s2 lone pair with O orbital due to La3+ substitution. La substitution in the Bi-based compound is suggested reduce MnO6 octahedral distortion hence increasing delocalization of charge carriers. The observed variation in MR behavior due to La substitution indicates the substitution influence the MR mechanism of extrinsic and intrinsic behavior in Bi0.3-xLaxPr0.3Ca0.4Mn0.1Cr0.9O3 .Â

New fabricated electrolytes based on Dy3+-Tm3+ double-doped δ-Bi2O3-type cubic phase

(Bi2O3)1-x-y(Dy2O3)x(Tm2O3)y ternary systems as electrolytes were synthesized at 750 °C by the solid-state ceramic synthesis method. Eight (Bi2O3)1-x-y(Dy2O3)x(Tm2O3)y (x = 0.1, 0.2) and (y = 0.05, 0.1, 0.15, 0.2) electrolytes at different ratios were investigated. The structural, electrical, and thermal properties of these eight electrolytes for solid oxide fuel cells (SOFCs) were characterized by means of a X-ray powder diffractometer (XRD), the four point-probe technique (4PPT), and thermal gravimetry/differential thermal analysis (TG/DTA). Results of XRD measurements showed that the δ-Bi2O3 (cubic) phase with a stable structure was dominantly obtained for all of the samples. As a result of the temperature-dependent electrical measurements of these ternary systems, it was found that electrical conductivity decreases with increasing molar ratio of Tm2O3. The highest electrical conductivity was found for the sample of the (Bi2O3)0.85(Dy2O3)0.10(Tm2O3)0.05 system as 0.349 (Ω cm)−1 at 750 °C. The lowest activation energy was found for the same sample as 0.68 eV.

Thermoelectric performance of (GeTe)1−x(Sb2Te3)x fabricated by high pressure sintering method

(GeTe)1−x(Sb2Te3)x is one of good middle temperature thermoelectric materials. Here, the effects of x values and heat treatment (673 K 24 h) on the thermoelectric property of (GeTe)1−x(Sb2Te3)x (x = 0, 0.02, 0.04, 0.06) prepared by solid-state synthesis (873 K) and high pressure sintering (6 GPa) method were studied, the composition, microstructure, and the thermoelectric properties in temperature range of 300–731 K were investigated. The results indicate that high pressure sintering (HPS) is beneficial to the dissolution of Sb2Te3 in GeTe and the acquisition of nanocrystalline (GeTe)1−x(Sb2Te3)x. Soluble Sb2Te3 can greatly change the crystal structure of GeTe, and results in the high pressure phase and different thermoelectric property in (GeTe)1−x(Sb2Te3)x (x ≠ 0). Heat treatment does not change the high pressure phase of (GeTe)1−x(Sb2Te3)x (x ≠ 0), meanwhile it increases the crystal grain size of (GeTe)1−x(Sb2Te3)x (x ≠ 0). Samples of x = 0.04 and x = 0.06 show the maximum Seebeck coefficient value at 724 K, and (GeTe)0.98(Sb2Te3)0.02 shows the highest power factor (PF = 3.70 μW/mmK2 at 724 K). The largest value of ZT = 0.56 at 724 K is obtained for (GeTe)0.94(Sb2Te3)0.06.

Fabricated Electrochemical Sensory Platform Based on the Boron Nitride Ternary Nanocomposite Film Electrode for Paraquat Detection.

Hexagonal boron nitride (BN), an effective diffusion material for mass transport, was functionalized with molybdenum disulfide (MoS2) and Au nanoparticles (Au NPs). Then, the working electrodes with developed nanomaterials were applied to construct an electrochemical paraquat sensor. BN was prepared using a solid-state synthesis method combined with solvent-cutting. The electrochemical properties of the BN/MoS2/Au NP-based glassy carbon electrode (GCE) were investigated using differential pulse voltammetry and cyclic voltammetry. An excellent response signal to paraquat was found from 0.1 to 100 μM with a limit of detection of 0.074 μM, and it had acceptable reproducibility (relative standard deviation = 2.99%, n = 5) and good anti-interference ability. The modified GCE showed superior performance owing to the synergistic effects among all three given nanomaterials. With the proposed method, paraquat in grass samples from an orchard was then investigated. The results of the electrochemical analysis agreed with those of experiments and obtained a 96.28% confidence level via high-performance liquid chromatography, exhibiting relatively high stability. Therefore, the fabricated sensor can be a candidate for the determination of paraquat.

Effect of Fe3+ for Ru4+ substitution in disordered Na1.33Ru0.67O2 cathode for sodium-ion batteries: Structural and electrochemical characterizations

Sodium ruthenium oxides (Na2RuO3 and Na1.33Ru0.67O2) belong to a special Na-rich type of cathode material which show high specific capacities and structural stability. Even though these Na-rich materials possess attractive electrochemical properties, owing to the low abundance of ruthenium (Ru) within the Earth’s crust, commercialization of sodium ruthenium oxide (NRO) cathodes is extremely difficult. To mitigate this disadvantage, we have substituted Ru in NRO using Fe, which is electrochemically active in many cathode materials for sodium-ion batteries (SIBs), Earth-abundant and cheap. Herein, a series of Fe-substituted (Fe% = 5 mol. %, 10 mol. %, 20 mol. %, and 30 mol. %) sodium ruthenium iron oxide (NRFOx) phases were synthesized using a conventional solid-state synthesis method. When used as a cathode material, among these novel Fe substituted phases, the composition with the lowest Fe mol. % displays the highest specific discharge capacities of 115 mAh g−1 and 61 mAh g−1, at 0.2C and 2C rate respectively, within a 2.0–3.7 V potential range. It was seen that the Fe substitution level significantly influences structural stability and discharge capacities. Cyclic voltammetry displays that Fe3+ is surprisingly electrochemically inert inside the NRO matrix and only plays a structural role.

Uniaxial negative thermal expansion in the mullite- and borax-type PbAlBO4 polymorphs

This study presents an investigation on the axial negative thermal expansion of α-PbAlBO4 and β-PbAlBO4. Polycrystalline and single-crystal samples were prepared by solid-state synthesis method, characterized by temperature- and pressure-dependent X-ray and neutron diffraction experiments. The axial negative linear compressibility (NLC) is known for the α-polymorph, although structurally different the β-polymorph also shows similar NLC phenomenon. The lattice thermal expansion was described using the first-order Gruneisen equation of state, where the vibrational energy was calculated using the Debye–Einstein-Anharmonicity model. The density functional theory (DFT)-based phonon density of states and Raman spectra helped to choose the characteristic frequency to model the metric parameters. Lattice thermal expansion was additionally simulated in the quasi-harmonic approximation using the plane-wave DFT approach at the PBEsol level. The apparent departure of the quasi-harmonic approximation model has been discussed in terms of associated thermodynamic functions. The interplay between the topology-induced negative cross-compliance and anisotropic Gruneisen parameter has been identified as the driving force for the axial negative linear compressibility and axial negative thermal expansion.

On Improving the Cycling Stability of P2-Type Na0.67Ni0.33Mn0.67O2 Cathode Material By Ti-Substitution for Na-Ion Batteries

The extensive studies over the last decade have established Na-ion batteries (NIBs) as one of the cheaper alternatives to Li-ion batteries (LIBs) [1-2]. P2-type Na0.67Ni0.33Mn0.67O2 has stood out among layered oxide based electrode materials providing the best over-all electrochemical performance. The electrodes can exert up to 92.5% of its theoretical capacity (160 mAhg-1) at a voltage higher than 3 V accounted for the Ni2+/Ni4+ redox. However, at higher voltages, electrodes suffer irreversibility due to P2-O2 structural transition [3]. Recent studies in suppressing this transition by partial substitution with various metals on either Ni or Mn lattice site have suggested enhancing cycling stability [4-7]. In this study, a novel cathode material with Ti-substitution on Ni site, P2-type Na0.67Ni0.25Ti0.08Mn0.67O2 has been synthesized via solid-state synthesis method and characterized electrochemically. Na0.67Ni0.25Ti0.08Mn0.67O2 electrodes have been observed to be highly reversible at higher voltage ranges. The electrodes have an initial discharge capacity of 125 mAhg-1 and can retain around 84% of this capacity (105 mAhg-1) even after 50 cycles at 0.1C when cycled at an upper cut-off voltage of 4.3 V (Figure 1). Na0.67Ni0.25Ti0.08Mn0.67O2 electrodes are believed to suppress the irreversible P2-O2 transformation by diverting the charging reaction through a more reversible P2-OP4 transition.

Single Step Solid-State Synthesis of Lanthanum Molybdate

Abstract In this study, LaxMoyOz powders were synthesized by a cost-effective solid-state synthesis method. Four different heating cycles were designed to investigate the effects of synthesis temperature and holding time on lanthanum molybdate (LMO) formation, phase assemblies, particle size and morphology. X-Ray Diffraction (XRD) and scanning electron microscopy (SEM) studies were performed to observe crystal structure and particle morphology of synthesized powders. The results showed that nearly ninety percent β - La2Mo2O9 (43,3 nm crystal size) phase was obtained at 1000 °C for 6 h holding time. Longer holding times at 1000 °C favor more oxygen-rich compounds which cause recrystallization of various new crystalline phases. The grain size of the synthesized powder was increased from 0,2 µm to 1,5 µm with increasing holding time. In summary, it is possible to manufacture LMO powders rich in β - La2Mo2O9 by one - step solid - state synthesis method. The phase assembles and particle size of LMO powders could also be tailored by optimization of heat treatment cycle.

Correction to: Crystal Structure and XANES Study of Defect Perovskite (Y1−xPrx)1+δBa2−δCu3O7−y Compounds Prepared by Solid State Synthesis Method

In this research, the processing and characterization of (Y1−xPrx)1+δBa2−δCu3O7−y cuprate perovskite powder were studied. The experimental powder samples of (Y1−xPrx)1+δBa2−δCu3O7−y (0 ≤ x ≤ 1) were prepared using a conventional solid-state reaction method. The starting powders in appropriate ratios were mixed with 6 mol% excess of A-site ions to reduce the amount of BaCuO2 and PrBaO3 second phases and calcined at 880 °C for 12 h in normal atmosphere. The calcined powders were investigated for phase content using X-ray diffraction technique and detailed structural parameters were obtained by Rietveld refinement. The microstructure of the powders was investigated by scanning electron microscopy (SEM). The chemical composition was carried out by energy dispersive X-ray analysis (EDS). The oxidation state and coordination of Pr and Cu were determined by X-ray absorption near edge structure (XANES) spectroscopy. It was found that high-purity (Y,Pr)BCO powders could be obtained. By the Rietveld refinement, the overall unit cell volume increased with increasing Pr content. SEM–EDS images showed that the particle size was about 1–5 μm and the elemental composition of (Y + Pr):Ba:Cu = 1:2:3. Pr and Cu XANES spectra indicated that the average formal valence was larger than 3 for Pr and 2 for Cu. However, the peak shifted to lower valence state at higher concentration of Pr.

Effect of Sintering Additives on Structural, Magnetic, and Dielectric Properties of Ba3Co2Fe24O41 Ferrite

Z-type Ba3Co2Fe24O41 (Co2Z) ferrite with different additives (Bi2O3, SiO2, Al2O3, and MgO) was prepared by solid-state synthesis method. Effect of sintering additives on structural, magnetic, and dielectric properties has been investigated. All XRD patterns confirmed the single-phase Z-type ferrite; however, a minor trace of M-type ferrite was observed with SiO2 additive. FTIR studies verified that the additive ions do not occupy any crystallographic sites of Co2Z ferrite. SEM micrographs revealed that SiO2, Al2O3, and Bi2O3 promote hexagonal platelet-shaped structure of different size. Magnetic measurements showed that coercivity increased and saturation magnetization decreased with sintering additives. All the sintering additives effectively reduced complex permittivity and dielectric losses of Co2Z ferrite.