Standard Solid-state Reaction Method Research Articles

Investigation of Structural, Dielectric and Electrical Properties of Barium Titanate Ceramics Co-Doped with Bismuth and Yttrium

Bismuth and Yttrium co-doped Barium Titanate (BaTiO3) ceramics with the general formula (Ba[Formula: see text]BiX) (YxTi[Formula: see text]) O3(where [Formula: see text], 0.01, 0.03, 0.05) have been synthesized at 1300∘C for 3[Formula: see text]h by the standard solid-state reaction method. The prepared samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Impedance Analyzer. Temperature-dependent dielectric properties of the samples were also measured. The XRD result revealed perovskite structure for un-doped and co-doped BaTiO3with tetragonal phase. However, with increasing doping concentration, a Pseudo cubic phase occurs also confirmed by the twin peaks (002) and (200) of XRD pattern. From SEM micrograph, submicron size particles were observed for all synthesized BaTiO3samples and exhibit a narrow size distribution with quiet uniform morphology. The crystalline size for un-doped BaTiO3found was 24.26[Formula: see text]nm, the size decreases (minimum 19.59[Formula: see text]nm for [Formula: see text]) for all compositions of co-doped BaTiO3. Dielectric constant values were apparently high and direct current (DC) resistivity follows a decreasing trend at higher doping concentration. The sample doped with [Formula: see text] shows minimum DC resistivity and maximum dielectric constant among the samples investigated.

Synthesis and Elucidation of Structural, Morphological, Magnetic, and Electrical Properties of Al3+ Substituted Ba0.7Sr0.3Ti1 − xAlxO3 Perovskites

In this paper, the structural, morphological, magnetic, and electrical properties of Al3+ substituted Ba0.7Sr0.3Ti1 − xAlxO3 (where x = 0, 0.05, 0.10, 0.15, 0.20) perovskites were properly elucidated which were successfully synthesized by the standard solid-state reaction method. All the compositions were calcined at 700 °C for 4 h and sintered at 1150 °C for 4 h. The XRD patterns of all the prepared compositions were of single phase and showed good crystallinity. The crystalline phase was indexed as a simple cubic structure preferentially oriented along (110) plane. The lattice constant increased for the sample with Al content; x = 0.05 then decreased with further increase of Al content. FESEM images confirmed good microstructural and morphological properties with a homogeneous distribution of grains in the sample which was surrounded by a visible grain boundary. The result observed from VSM showed that all the compositions exhibited weak ferromagnetic properties at room temperature. The real part of complex permeability showed that the resonance frequency shifted towards higher frequency because Al3+ substitution and the quality factor increased at high frequency which indicated that the prepared perovskites had high-frequency magnetic applications. A high-quality factor was observed at a higher frequency which confirmed high-frequency dielectric applications of the prepared compositions. AC resistivity increased with the increase in Al content which indicated that the prepared perovskites had low eddy current loss characteristics.

Cr-doping effects on optical and magnetic properties of BaSn1−xCrxO3

Polycrystalline bulk samples of BaSn1−xCrxO3 with different Cr concentrations were prepared by standard solid state reaction method. The effects of Cr concentration on crystal structure of BaSn1−xCrxO3, as well as optical and magnetic properties were investigated. Powder X-ray diffraction (XRD) shows that each of these samples possess a perovskite structure with $$ Pm\bar{3}m $$ space group. The Cr ions are located at the substitution Sn sites as revealed by the XRD, Diffuse reflectance spectra and Raman spectra. Moreover, it is found that room-temperature ferromagnetism (FM) can be reversed by annealing in the nitrogen atmosphere. This can be well explained by a modified model of F-center mediated FM.

Effects of structural transition on microwave dielectric properties of Sr3(Ti1-xSnx)2O7 ceramics

Sr3(Ti1-xSnx)2O7 (x = 0–1.0) ceramics were prepared via a standard solid-state reaction method. X-ray diffraction patterns and Rietveld refinement results indicated a composition induced onset of octahedral tilting when x > 0.2, and the crystal structure transformed in sequence: tetragonal (I4/mmm) → coexistence of tetragonal and orthorhombic (I4/mmm + Amam) → orthorhombic (Amam). The τf value could be successfully tuned towards zero and the effects of octahedral tilting on the evolution of τf value were emphasized. Meanwhile, the role of tolerance factor in tailoring the resultant τε of the present ceramics was revealed and compared with the empirical rule for complex perovskites. Qf value decreased monotonously with increasing x, which could be elucidated by the variations of extrinsic parameters and intrinsic dielectric loss extrapolated from the infrared reflectivity spectra. The optimum microwave dielectric properties were achieved at x = 0.8 (εr = 18.6, Qf = 45,250 GHz, τf =–14 ppm/oC).

Effects of (Mg1/3Nb2/3) substitution on the structure and microwave dielectric properties of Sr2TiO4 ceramics

Sr2Ti1−x(Mg1/3Nb2/3)xO4 (0 ≤ x ≤ 0.4) solid solutions were synthesized by standard solid-state reaction method for the first time, and their microwave dielectric properties were systematically investigated together with the microstructure. X-ray diffraction patterns revealed the formation of solid solutions in the whole composition range, while two kinds of secondary phases started to appear when x = 0.4. With increasing x , the dielectric constant (εr) was tuned from 42 to 26.3 and the temperature coefficient of resonant frequency (τf) could be successfully modified from 130 ppm/°C to 46.3 ppm/°C. Excellent combination of microwave dielectric properties with εr = 28.5, Qf = 83,300 GHz, and τf = 53 ppm/°C were obtained for the x = 0.3 composition after sintering at 1500 °C for 3 h.

Effect of temperature on physical properties of Bi2Fe4O9 polycrystalline materials

In the present study, Bi2Fe4O9 polycrystalline powders have been prepared using standard solid-state reaction method. The function of the processing parameters such as chemical reaction, heating and cooling temperature rate, and sintering time on the single-phase formation mechanism was investigated. The prepared Bi2Fe4O9 bulk has been sintered on different temperature from 500 to 800 °C in air to eliminate the organic impurity. The powder X-ray diffraction (PXRD) analysis confirms that Bi2Fe4O9 bulk has typical orthorhombic phase with few intermediate impurities Fe2O3/Bi2O3. The average crystallite size of Bi2Fe4O9 polycrystalline materials has been calculated from Scherer formula and found to be in the range of 60–100 nm. The atomic force microscopy (AFM) reveals that the spherical particles are closely packed to each other. The particle size increases with increasing the sintering temperature of Bi2Fe4O9 bulk. The M-H measurement shows that Bi2Fe4O9 materials have weak ferromagnetic behavior at room temperature. The dielectric constant e′ increases and the tangent loss decreases with increasing sintering temperature, which indicates that it improves the ferroelectric properties.

Magnetic Properties and Magnetic Entropy Changes of Eu-Doped La0.9Sr0.1MnO3 Perovskite Manganese Oxides

Polycrystalline samples of La0.9−xEuxSr0.1MnO3 (x = 0.00, 0.05) were prepared using the standard solid-state reaction method. The effects of Eu3+ doping on the magnetic properties, magnetic entropy changes, and critical behaviors of La0.9Sr0.1MnO3 polycrystalline samples were systematically investigated. Preformed cluster phases were present in both samples in the temperature ranges of 118–326 K and 121–329 K, respectively. Additionally, near the Curie temperature (TC), the samples exhibited a second-order transition. The critical behaviors of the two samples were best fitted with the mean field model. The maximum magnetic entropy changes $$ \left| {\Delta S_{\text{M}} } \right| $$ of the two tested samples at 7 T near TC were 2.76 J K−1 kg−1 and 2.53 J K−1 kg−1, respectively; in addition, their relative cooling power was 425.28 J kg−1 and 354.93 J kg−1, respectively. The maximum magnetic entropy change calculated from the fitted data was in close agreement with the experimental data. These results indicate that the samples have the potential to realize magnetic refrigeration in the high-temperature regime (T > 77 K).

Modeling of Micro-Hardness in the Au-Doped YBCO Bulk Superconductors

In this study, in order to investigate the effect of Au doping on mechanical properties of YBCO, Au-doped (from x = 1 wt% to x = 20 wt%) and pure YBa2Cu3O7-x samples were prepared by standard solid-state reaction method. The indentation load versus diagonal length of the samples under various indentation loads in the range of 0.245–2.940 N is measured. The micro-indentation measurements showed that the load-dependent micro-hardness value for Au-doped samples is lower in comparison with that of the pure sample. The values of the hardness are found to be load and Au content-dependent. For each sample, the reverse indentation size effect (RISE) is observed in which micro-hardness value increased with increasing the load. In addition, we extract the load-independent (true) micro-hardness using Meyer’s law, Kick’s law, proportional specimen resistance, modified proportional specimen resistance, the Hays-Kendall, and the indentation-induced cracking (IIC) models and compare the true hardness with the apparent hardness. Among the investigated models, IIC model is determined to be the most successful one describing the mechanical properties of our samples.

Giant electrocaloric effect in 0.75PbZrO3 - 0.25Bi(Mg1/2Ti1/2)O3 ceramics

Abstract Antiferroelectric (AFE)/ferroelectric (FE) materials with large electrocaloric effect (ECE) in a broad operating temperature range are potential candidates for next generation solid-state refrigeration applications due to its environmentally-friendly and high efficiency. In this work, we have experimentally investigated the electrocaloric response in 0.75PbZrO3-0.25Bi(Mg1/2Ti1/2)O3 in ceramics by prepared by a standard solid-state reaction method. Ferroelectric P-E hysteresis loops were measured over a broad range of temperature/electric field and the ECE was calculated by the indirect thermodynamic method. The maximum value of ECE ( Δ T) and the electrocaloric responsivity ( Δ T/ Δ E) were found to be 0.96K and 2.43 × 10−7 K.mV−1, respectively, at an operating temperature of 366 K under the external electric field of 40kV/cm. The observed ECE response has the great potential for their uses in solid state cooling technology applications.

Superconducting Properties of Te-Substituted (Tl<sub>2-</sub><i><sub>x</sub></i>Te<i><sub>x</sub></i>) Ba<sub>2</sub>CaCu<sub>2</sub>O<sub>8-δ</sub>

The Tl2-xTexBa2CaCu2O8-δ (Tl-2212) high temperature superconductors with x = 0.0-0.5 have been prepared by the standard solid-state reaction method. The precursor powder were sintered at 900°C for 24 h with several grindings and heating. The powder were then pressed into pellets and heated at 910°C in oxygen flow for 4 min followed by furnace cooling. The electrical resistance versus temperature dependence measurements showed metallic normal state behavior for all samples. Substitution of Te at the Tl-site led to multi-phasic samples. The x = 0.4 sample showed the highestTc zero= 98 K and Tconset= 111K. The Tl-2212 phase increased from 50% for x=0 up to 92% in the x= 0.4 sample.

Technology and electrophysical properties of the (K0.44Na0.52Li0.04)(Nb0.9–xTa0.1Sbx)O3 ceramics

ABSTRACTCompounds based on (KzNa1–z)NbO3 (KNN) are promising lead-free ferroelectric materials that reveal good electrophysical properties. In the present work, we report the results of the study influence of the doping effect of antimony on the technology, microstructure and electrophysical properties of potassium sodium niobate ceramics modified by lithium and tantalum ions (K0.44Na0.52Li0.04)(Nb0.9–xTa0.1Sbx)O3 (KNLNTSbx). The four KNLNTSbx ceramic compositions were designed:(K0.44Na0.52Li0.04)(Nb0.9Ta0.1)O3 (for xSb = 0),(K0.44Na0.52Li0.04)(Nb0.88Ta0.1Sb0.02)O3 (for xSb = 0.02),(K0.44Na0.52Li0.04) (Nb0.87Ta0.1Sb0.03)O3 (for xSb = 0.03),(K0.44Na0.52Li0.04) (Nb0.86Ta0.1Sb0.04)O3 (for xSb = 0.04).All ceramic powders were synthesised by the standard solid-state reaction method from the mixture of oxides and carbonates. The paper presents the technology and results of crystal structure, microstructural, dielectric properties, as well as DC electrical conductivity of the KNLNTSbx ceramics. The conducted research proved that suitable doping of the KNN materials improves the sinterability of the ceramic compositions and positively influences the useful electrophysical properties thereof.

Degradation in fundamental characteristic features of Bi-2212 superconducting ceramic material with Sr/Ti partial substitution

The present work investigates the vital differentiations in some basic characteristic properties including the crystallinity quality, flux pinning mechanism, superconducting, dc electrical features, grain boundary coupling problems and strength of connection between the superconducting grains in the poly-crystallized Bi2.1Sr2.0−xTixCa1.1Cu2.0Oy cuprate ceramic materials with the partial aliovalent substitution of Sr2+ impurities for the Ti4+ foreign additives in the crystal system. All the materials are prepared by the standard solid-state reaction method, and the characterization of samples produced is thoroughly performed by the typical experimental measurements such as dc electrical resistivity over the temperature, critical current density and powder X-ray diffraction investigations. It is obvious that all characteristic properties tend to diminish constantly with the augmentation of the aliovalent Sr/Ti partial replacement level, and in case of x = 0.10 they reach the global minimum values. To illustrate, the low Bi-2212 superconducting phase diverges from the stabilization because of new induced permanent crystal structure (crystallinity) problems such as the voids, porosity, defects, texturing, cracks, grain boundary coupling problems, grain alignment distributions, stress raisers, omnipresent flaws and crack initiation sites in the crystal system. Besides, the presence of Ti impurities leads to the formation of new impurity phases related to very low superconducting and characteristic TiO2 phase, being favored by either the decrement of c lattice cell parameter or increment of a-axis length. The similar findings are observed in the temperature dependent electrical resistivity measurements. Namely, the electrical resistivities at the normal state are found to increase dramatically from about 74.75–180.47 mΩcm whereas the offset and onset critical temperature values are recorded to diminish from 82.11 K (for the pure sample) to 50.52 K (for the sample prepared with x = 0.10 substitution level) and 84.03–75.14 K, respectively, with the enhancement in the substitution level. Likewise, the Sr/Ti partial replacement affects negatively not only the thermal fluxon motions of correlated two-dimensional pancake vortices but also the ability and strength of vortex lattice period, elasticity, effective and active energy barriers for the flux pinning centers in the Bi-2212 superconducting crystal lattice. In this respect, the Sr/Ti partial substitution mechanism is ploughed to improve the fundamental characteristic features.

Trap level analysis of Ce3+ and Sm3+ in Li6Y(BO3)3

Abstract The polycrystalline compounds of Li6Y(BO3)3: Ce3+ and Sm3+ co-doped polycrystalline samples were prepared by using standard solid state reaction method. The energy levels of the doped lanthanide ions (Ce3+ and Sm3+) in the borate host materials were investigated by Thermoluminescence (TL) glow peak analysis. The co-doped samples, exhibits the TL peak at higher temperature region around 511 K whereas the Ce3+ individually doped sample has peak around 433 K. The X-ray excited emission spectra were carried out for all the prepared samples and found the characteristic emission bands. The trap depths (E) were calculated by using several standard methods, namely peak shape method or chen's (PS), variable heating rate (VHR), initial rise (IR) and computerized glow curve deconvolution (CGCD). The mean activation energy of the co-doped samples found to be 1.21 (0.07±) eV and the frequency factor around 1.38 × 1011 Sec−1. The calculated trap depths and the predicted energy level values were compared and found in good agreement. This primarily results suggest that the energy level scheme can help in the development of new TL materials suitable in dosimetry.

Marked influence of low Bi doping levels on the structural and thermal transport properties of nonstoichiometric 0.98 PbTiO3 ceramics

Abstract X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric characterization methods were used to study the effect of Bismuth (Bi) on the phase structure, microstructure and electrical response of nonstoichiometric 0.98 PbTiO3 (PT) ceramics. Standard solid state reaction method was adopted for the preparation of compositions. Pre fired polycrystalline PT ceramics prepared with 0.98 Pb/Ti molar ratio were doped with Bismuth ( V o • • vacancies.

Magnetic properties and magnetic entropy change of perovskite manganites La0.9–xEuxSr0.1MnO3 (x=0.000, 0.075) by experimental method and numerical fitting

Polycrystalline samples La0.9-xEuxSr0.1MnO3 (x = 0.000, 0.075) were prepared by the standard solid-state reaction method. The results show that the samples preform a characteristic of clusters spin-glass state at low temperature. The samples show a characteristic of ferromagnetism (FM) characteristic in the temperature range of 15–125 K and 15–150 K respectively; the samples show preformed clusters in the temperature range of 125–343 K and 150–325 K, respectively, the samples show paramagnetism (PM) characteristic above 343 and 325 K, respectively. The second-order transitions are found at 118 and 135 K for undoped and doped sample, respectively. When the applied magnetic field is 7 T, the maximum magnetic entropy change |ΔSM| value of the samples is near the Curie temperature (TC), and the value of |ΔSM| reaches 2.76 and 3.03 J/(K·kg), respectively. In addition, the relative cooling power (RCP) is found to be 425.28 and 443.53 J/kg. The numerical fitting data fit well with experimental data. These results indicate that both the samples have the potential to realize magnetic refrigeration in the high temperature region (T > 77 K).

3Photoluminescence study of activator ions (Eu, Tb) co-doped in different host environments (CaO, CaSiO3, CaAl2O4 and CaSiAl2O6)

Abstract The present paper mainly reports on how the co-doped RE activator ions behaves especially the excitation and emission wavelengths, in different host environments. For this purpose, we have taken Eu and Tb rare-earth ions as activators or dopants at 1.5 mol%, 1.0 mol% respectively. These dopants are co-doped in different host materials like CaO, CaSiO3, CaAl2O4 and CaSiAl2O6 compounds and were synthesized by the standard solid state reaction method. The structure, morphology of the phosphors was characterized by X-ray diffraction and scanning electron microscopy. Luminescence properties of all the phosphors were investigated by the excitation and emission spectroscopy at the room temperature. The excitation spectra of all the synthesized phosphors monitored at 614nm wavelength were composed of a broadband around 310nm with high intensity which is attributed to charge transfer (CT) band from Eu – O and a series of sharp peaks with less intensity at 395nm and 467nm are observed which are assigned to f-f transitions of Eu ion. The emission spectra of prepared phosphors had transitions of Eu3+ ions i.e. 5D0 → 7F1 (590nm), 5D0 → 7F2 (614nm). CIE analysis and CCT were also done to see the colour coordinates and temperature of the phosphors. The prepared materials had bright red emitting optical properties that could be suitably applied in various display devices under UV excitation and also for w-LED applications under nUV, blue excitation.

Synthesis, crystal structure and microwave dielectric properties of Sr2LnMgNbO7 (Ln = La, Nd, Sm) novel compounds with Ruddlesden-Popper structure

Sr2LnMgNbO7 (Ln = La, Nd, Sm) novel compounds were prepared via standard solid-state reaction method, and their crystal structures and microwave dielectric properties were systematically investigated for the first time. X-ray diffraction (XRD) results indicated that pure Sr2LaMgNbO7 and Sr2NdMgNbO7 ceramics were synthesized, while some additional diffraction peaks corresponding to the perovskite-type secondary phases were observed in the Sm composition. Rietveld analyses indicated that Sr2LnMgNbO7 (Ln = La, Nd) compounds belonged to the n = 2 type Ruddlesden–Popper structure with general formula of An+1BnO3n+1, and their space groups were confirmed to be I4/mmm with tetragonal crystal symmetry. The detailed structural information of Sr2LaMgNbO7 and Sr2NdMgNbO7 compounds were revealed and their corresponding microwave dielectric properties were evaluated.

Structural, magnetic and electric properties of multiferroic NiFe2O4-BaTiO3 composites

Abstract The room-temperature magnetoelastic coupling has been demonstrated in (x)NiFe2O4 + (1 − x)BaTiO3 (where x = 0–1 with a difference of 0.1) composite system by investigating its structural, magnetic and ferroelectric properties. The samples were prepared by the standard solid-state reaction method and characterized by x-ray diffraction, backscattered scanning electron microscopy and energy dispersive x-ray spectroscopy techniques. The temperature dependent magnetization data clearly show significant jumps in magnetization curves at structural phase transitions of BaTiO3, signifying the strain-mediated converse magnetoelectric (CME) coupling in NiFe2O4-BaTiO3 multiferroic system. The substantial changes observed in the obtained parameters from structural, magnetic and ferroelectric properties clearly ensure the strain-mediated magnetoelectric (ME) as well as CME effects in this system. The present investigation indicates that the NiFe2O4-BaTiO3 composite system will be a potential candidate for the future low-power consumption device applications at room temperature.

Enhancement in magnetic and electrical properties of Ni substituted Mg ferrite

Abstract In this work, Ni substituted magnesium spinel ferrites having general formula Mg1−xNixFe2O4 (where x = 0.0, 0.1, 0.15, 0.2, 0.25 and 0.3) were synthesized by standard solid state reaction method. All the samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), DC resistivity measurements. X-ray diffraction analysis confirmed the single spinel phase. The lattice constant decreased with increasing Ni content due to the difference in the ionic radii of Mg2+ and Ni2+ ions. The FT-IR spectra reveled two prominent frequency bands in the wave number range of 400 cm−1 to 600 cm−1, which confirmed the cubic spinel structure of obtained compound and completion of chemical reaction. Magnetic studies revealed that the saturation magnetization increased with the substitution of Ni. The increase in magnetization was explained on the basis of distribution of magnetic and non-magnetic cations among A and B sites of the spinel lattice. A significant influence of cation distribution on DC electrical resistivity and activation energy was observed.

Synthesis of type-II based (1-x)Ba0.6(Ca1/2Sr1/2)0.4Ti0.5Fe0.5O3+(x)Ni0.40 Zn0.45Cu0.15Fe1.9Eu0.1O4 composites via standard solid state reaction method and investigation of multiferroic properties

A series of multiferroic composites, (1-x)Ba0.6(Ca1/2Sr1/2)0.4Ti0.5Fe0.5O3+(x)Ni0.4Zn0.45 Cu0.15Fe1.9Eu0.1O4 ((1-x)BCSTFO+(x)NZCFEO) where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0 have been synthesized by standard double sintering ceramic method sintered for 3 hours at 1200°C in air. The X-ray diffraction patterns reveal that the multiferroics and the parent ceramic samples crystallize in simple cubic structure with a slightly distored lattice parameter. The X-ray and bulk density increase with the increasing ferrite content. Consequently, the porosity decreases indicating better crystallization. A decreasing trend in dielectric constant is observed while the relative quality factor (RQF) increases significantly with the increasing ferromagnetic NZCFEO. At the same time, M–H hysteresis loops reveal that ferromagnetic property enhances with the addition of Ni0.40Zn0.45Cu0.15Fe1.9Eu0.1O4 (NZCFEO). The highest values of coercive field ∼ 92 O and saturation magnetization ∼1.37 emu/g are observed for x = 10% and x = 50% compositions respectively. Additionally, the permeability enhances up-to x = 30% but decreases with further doping. The room temperature resistivity rises due to the decrease in hopping mechanism. The samples exhibit a decreasing trend for resistivity with the increase of temperature. The dopant concentration has also shown an impressive impact on the activation energy. As a result, the multiferroic properties of (1-x)BCSTFO+(x)NZCFEO have been significantly improved considering the measured magnetic and ferroelectric properties.