Increase Of Sr2 Research Articles

Ultra-high energy storage density in PBSLZS antiferroelectric thick film ceramics

Superior recoverable energy density (Wrec) and efficiency (η) are crucial parameters for capacitors used in pulse-power devices. Here, we achieved an ultrahigh Wrec and high η in (Pb0.95-xBa0.02SrxLa0.02)(Zr0.65Sn0.35)O3 (PBSLZS) antiferroelectric thick film ceramics. All ceramics exhibit an orthorhombic structure, and the forward switching field increases with the increase of Sr2+ ionic content. The PBSLZS (x = 0.03) ceramics exhibit maximum value of total energy density (Wtot) and Wrec of 14.9 J/cm3 and 12.9 J/cm3, respectively, along with a high η of 86.6% at 570 kV/cm. Furthermore, we investigated the impact of multi-field coupling, i.e., the electric field and temperature, on the energy storage performance. An electric field (E) versus temperature (T) phase diagram was also obtained. The outstanding energy storage performance observed in PBSLZS ceramics demonstrates the potential for energy storage capacitors.

Effect of Sr2+doping on the microwave dielectric properties of BaZrO3 ceramics

ABSTRACT In this study, undoped and Sr2+ doped BaZrO3 ceramics were prepared by solid-state reaction using 3 wt-% B2O3 as sintering aid. The phase composition and microstructure of BaZrO3 were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that introducing an appropriate amount of Sr2+ makes BaZrO3 ceramics Q × f value and density increase. In addition, the dielectric constant of BaZrO3 ceramics increases with the increase of Sr2+ addition. With excellent microwave dielectric properties, ϵ r = 34.17 and Q × f value of 39,070 GHz(@ 7.8 GHz) τf = + 140 ppm/°C were obtained in 6 at.-% Sr2+ doped BaZrO3 with 3 wt-% B2O3 sintering aid at 1275°C for 5 h. Using this material as the medium, the simulation of GPS antenna by HFSS software shows that this material has the potential to be used as the antenna medium material.

The effect of (Ni2+ + Sr2+) co-doping on structure and dielectric properties of Bi1.5MgNb1.5O7 pyrochlores

The dielectric properties of bismuth-based cubic pyrochlore largely depend on the A-site cation. The effect of (Ni2+ + Sr2+) co-doping on the structure and dielectric properties of Bi1.5MgNb1.5O7 (BMN) was investigated. It reveals that the Ni2+ and Sr2+ in the co-doped Bi1.5Mg0.5NixSryNb1.5O7 (BNSN, x = 0.0–0.3 mol%, y = 0.0–0.2 mol%) ceramics preferentially replaced the Mg2+ on the A-site. For the samples with x = 0.3 and y < 0.2, it showed a very low dielectric loss (∼0.0003, 1 MHz). The dielectric loss of BNSN gradually increased with the increase of Sr2+ doping. However, the dielectric constant increased with increasing Sr2+ content. The BNSN exhibited a large dielectric constant (∼166, 1 MHz) at x < 0.3 and y = 0.2. Ni-doping would reduce the oxygen vacancy, which in turn decrease the dielectric loss. While, the increasing dielectric constant is attributed to the high ion polarizability of Sr2+ ions.

Synergistic effect of dielectric resonance and plasma oscillation on negative permittivity behavior in La1-xSrxMnO3 single-phase ceramic

Ceramic-based composites with negative permittivity property can be realized by dielectric resonance or plasma oscillation, but it is still a challenge to integrate two kinds of negative permittivity into a single-phase material. In this study, the La1-xSrxMnO3 (LSMO) single-phase ceramic (x = 0.3, 0.4, 0.5, 0.6 and 0.7) was successfully fabricated by a sol-gel auto-combustion and pressureless sintering method. Just by adjusting the content of Sr2+, the Lorentz-like and Drude-like negative permittivity were simultaneously observed in LSMO ceramic under the synergistic effect of dielectric resonance and plasma oscillation. The amplitude of dielectric resonance was lessened because of the increase of damping factor, and the resonance frequency gradually moved to a lower frequency region with the increase of Sr2+. When the content of Sr2+ reached 0.7, the Drude-like negative permittivity played an overwhelming role due to an enhanced double-exchange effect in La1-xSrxMnO3. Meanwhile, the tanδ of LSMO was as low as 0.085, which was scarcely observed in previous investigations. The generation and regulation mechanism of negative permittivity was further clarified. This work opened up a way to adjust negative permittivity behavior in single-phase ceramic material which has great value in high-power microwave filters and wireless ring resonators.

Dielectric and microwave absorption properties of Na0.5Bi0.5TiO3–SrTiO3 system

In this work, we have investigated the structural, dielectric and microwave properties of Sr x (Na0.5Bi0.5)1– x TiO3 (0.25 ≤ x ≤ 0.75) prepared using the solid state reaction technique. The Rietveld refinement of the X-ray diffraction pattern at room temperature of the samples is performed to confirm the phase formation as well as the crystal structure of the materials. All the materials are synthesized in cubic Pm3m phase. The low-frequency dielectric properties of the materials are investigated using alternate current impedance spectroscopy in the frequency range from 50 to 1 MHz. The temperature dependence of the dielectric constant at different frequencies gives diffuse peaks which have been attributed to the occurrence of relaxor behavior in these materials. The magnitudes of ε′m, the maximum value of dielectric constant and T m, the temperature corresponding to ε′m are decreased with an increase of Sr2+ ion in the materials. The Vogel-Fulcher relation has been considered to explain the relaxor behavior of the materials. The microwave dielectric properties as well as reflection loss of the materials have also been studied in the frequency range from 1 GHz to 15 GHz.

Photoluminescence evolution and high thermal stability of orange red-emitting Ba3-xSrxZnNb2O9: Eu3+ phosphors

A series of Ba3-xSrxZnNb2O9: 0.3Eu3+ (x ​= ​0, 0.5, 1, 1.5, 2, 2.5, 3) orange-red phosphors were synthesized by high-temperature solid-phase reaction. In order to identify and describe the crystal structure, luminescence characteristics and thermal stability of the samples, XRD and luminescence spectroscopy tests were carried out. The refined XRD results showed that Eu3+ ions have been successfully doped into Ba3-xSrxZnNb2O9 matrix and occupied partly the sites of Eu3+ ions. Under UV excitation of 396 ​nm, the emission spectra of the samples are composed of two emission peaks near 593 ​nm and 612 ​nm with a slight blue shift, attributed to the increase in splitting degree of 5d electron orbit of Eu3+ ions. At 523 ​K, the thermal stabilities of phosphors with Sr2+ ion doping concentration of 2 and 3 are 82.14% and 84.33%, respectively. With the increase of Sr2+ ion concentration, the activation energy increases from 0.198 ​eV to 0.230 ​eV, better than the other reports. In addition, the CCT (below 2000 K) and color purity (above 95%) of the samples are calculated. A WLED device can be obtained by combining the as-prepared orange red-emitting phosphor with commercial blue (BaMgAl10O17: Eu2+) and green ((Sr, Ba)2SiO4: Eu2+) phosphors. All these indicated that the self-made phosphors are promising to be used in UV/n-UV pumped WLEDs requiring low CCT.

Investigation of flame spray synthesized La1-xSrxCoO3 perovskites with promotional catalytic performances on CO oxidation

To enhance the activity of catalysts for CO removal, the perovskite-type catalysts La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, and 0.8) with different Sr2+ doping amount were synthesized by flame spray synthesis (FSS) method. The perovskite-type catalyst synthesized by FSS has a much larger specific surface area (SSA) than that prepared by other conventional methods. The SSA of catalyst increases with the increase of Sr2+ doping amount and the SSA of La0.2Sr0.8CoO3 reaches 31.65 m2/g. Compared with other conventional methods, FSS method significantly improves the activity of catalyst and makes it close to the performances of catalysts with surface modification. The substitution of La3+ by Sr2+ promotes the generation of secondary phase Co3O4 and SrCO3. The catalytic activity of La1-xSrxCoO3 increases with the addition of Sr2+, which results from the increasing active sites and oxygen vacancies. Interestingly, La0.4Sr0.6CoO3 performs the highest activity for CO oxidation and the CO conversion reaches 50% at 148.6 °C and 90% at 165.9 °C. The oxidation of CO over La1-xSrxCoO3 catalyst may follow a combination of MvK and L-H mechanisms according to the experimental results of H2-TPR. Moreover, the catalyst exhibits good catalytic activity in consecutive oxidation cycles. In consecutive oxidation experiments with La0.4Sr0.6CoO3, the CO conversion reaches 50% at 168.8 °C and 90% at 197.8 °C in the eighth oxidation cycle. These results prove that FSS method can further improve the activity of catalysts and is suitable for the preparation of efficient catalysts.

A novel bright blue emitting (Ba/Sr)Al2Si3O4N4: Eu2+ phosphors synthesized with BaAlO4 as precursor

Abstract A series of novel blue-emitting Ba1-xAl2Si3O4N4: xEu2+ phosphors were successfully prepared by two-steps high temperature solid state reaction. The results of XRD and SEM showed that the two-steps method obtain less impurities than the traditional one-step method. The electronic band structure of BaAl2Si3O4N4 (BASON) host was calculated as a direct band gap of 3.662eV by the DFT method. The PLE spectrum of B1-xASON: xEu2+ showed a wide band excitation in the wavelength range of 250–450 nm, which can be well matched with n-UV chips. Based on crystal structural and fluorescence lifetime analysis, three emission peaks were obtained by gaussian fitting to explain the asymmetry of Eu2+ emission in the BASON phosphor. The optimal doping concentration of Eu2+ was x = 0.04. According to calculated critical distance (3.24 A) and a little overlap between PLE and PL spectra, the concentration quenching mechanism was confirmed as both of dipole-dipole interaction and radiation reabsorption. In addition, with the incorporation of Eu2+, the diffuse reflection spectrum of B1-xASON: xEu2+ presented a wide absorption peak in the range of 200–500 nm. The PL intensity of Ba0.96-ySryAl2Si3O4N4: 0.04Eu2+ tended to rise first and then fall with the increase of Sr2+ concentration. Impressively, the relative emission intensity at 473K still maintained 95.7% compared with room temperature (293K), which indicated the excellent thermal stability of BASON phosphor. Finally, the density of state (DOS) of Ba1-ySryAl2Si3O4N4 (y = 0, 0.5, 1) were calculated and analyzed to explain the deterioration of thermal stability with the increase of Sr2+ substitution.

Partial cation substitution of tunable blue‐cyan‐emitting Ba2B2O5:Ce3+ for near‐UV white LEDs

AbstractIn this study, Sr2+, Ca2+, Zn2+, and Mg2+ ions act to tune the emission band to the blue‐cyan region in BaxSryB2O5:Ce3+ (BSBO), BaxCazB2O5:Ce3+ (BCBO), BaxZnuB2O5:Ce3+ (BZBO), and BaxMgvB2O5:Ce3+ (BMBO) phosphors. A red shift occurs with the increase of Sr2+, Ca2+, Zn2+, and Mg2+ concentration, and a blue shift occurs when the concentrations of Sr2+, Ca2+, Zn2+, and Mg2+ exceed the critical value. The emission color can be tuned from deep blue (0.15, 0.12) to cyan (0.16, 0.27) upon 365 nm UV lamp excitation due to the crystal field splitting and centroid shifts. The excitation band shift to long wavelength by introducing ions, so that the synthesized phosphor can be better matched with the n‐UV chip. The emission intensity slowly decreases with the temperature increasing. Therefore, the BMBO:Ce3+, BZBO:Ce3+, BCBO:Ce3+, and BSBO:Ce3+ phosphors with relatively good thermal stability were synthesized, which could have potential applications in the n‐UV white LEDs.

Tunable photoluminescence in Ba1-xSrxSi3O4N2: Eu2+/ Ce3+, Li+ solid solution phosphors induced by linear structural evolution

A series of oxynitride phosphors, Ba1-xSrxSi3O4N2: Eu2+/ Ce3+, Li+ (0 ≤ x ≤ 0.5) have been synthesized through a solid state reaction method at a high temperature. The influence of Sr2+-doping on the structure and photoluminescence properties of Ba1-xSrxSi3O4N2: Eu2+/ Ce3+, Li+ was studied systemically. All of the samples were found to retain their hexagonal crystal structures with the linear lattice shrinking upon the increase of Sr2+ concentration, indicating that Ba2+ is substituted by Sr2+ to form the intermediate solid-solution compositions of Ba1-xSrxSi3O4N2. It is noteworthy that red shifts of about 30 and 7 nm in the emission spectra of Eu2+ and Ce3+-activated samples were observed, respectively, through the Sr substitution at Ba sites from 0 to 0.5, originating from the increment of crystal field strength and Stokes shift. The thermal quenching stability, fluorescence decay behavior and CIE values were discussed and compared. Based on these results, the Ba1-xSrxSi3O4N2: Eu2+ phosphors are considered to be potential candidate phosphors applicable to n-UV LED for solid-state lighting.

Structure and defect interaction mediated transport mechanism of mixed di-tri valent cation containing ceria-based Ionic conductors

The aim of this study is to investigate structure and electrical response of mixed di-tri valent cation containing Ce1-xHo0.1SrxO2-δ (x = 0.02–0.1) ionic conductor. The Rietveld analysis of X-ray diffraction profiles confirms the solubility limit of Sr2+ ions into ceria lattice upto x = 0.06 and the co-existence of secondary phase SrCeO3 afterwards. With the increase of Sr2+ ions into ceria, formation of defect cluster increases and concentration of free oxygen vacancies decreases. The composition x = 0.06 shows lowest conductivity due the highest association energy of defect clusters. The dielectric constant plays a crucial role for the formation of defect clusters and conductivities of the compositions. The presence of SrCeO3 and depletion of oxygen vacancies at grain boundary region enhance the grain boundary resistances. The dielectric constant of grain boundary region affects the grain boundary conductivity.

An insight into the structure, conductivity and ion dynamics of Sr-Sm co-doped ceria oxygen ion conductors: Effect of defect interaction

In this work, we investigate the structure, conductivity and ion dynamics of mixed di and tri-valent doped Ce0.8Sm0.2-xSrxO2-δ (x = 0–0.2) oxygen ion conductors. The lattice parameter and root mean square strain are significantly affected by the ionic radius of dopants and their solubility into ceria lattice. Due to the solubility limit of Sr2+ ions, SrCeO3 phase increases with the doping concentration of Sr2+. The increase of Sr2+ ions into ceria lattice promotes the formation of large defect clusters by expense of formed oxygen vacancies. The coulombic interaction between oxygen vacancies with substituted dopant cations enhances with Sr2+ ions due to decrease of the value of dielectric constant of the compositions. The defect interaction significantly affects the conductivity values by means of increase of SrCeO3 phase and defect clusters. The conductivity values are found to be consistent with the migration and association energy. The scaled spectra of dielectric tangent loss and real part of complex conductivity confirm the temperature and defect interaction independent nature of hoping mechanism in the compositions.

Investigation on thermoelectric properties of screen-printed La1-xSrxCrO3-In2O3 thermocouples for high temperature sensing

La1-xSrxCrO3-In2O3 thick film thermocouples were fabricated by screen-printing method for high temperature sensing and the effects of Sr2+ content were investigated systematically. All La1-xSrxCrO3 thick films showed well crystallization with orthorhombic unit cell. Their average particle sizes showed the tendency of first increase then decrease gradually with the increase of Sr2+ content, and the maximum of average particle size was 1.76 μm. At the same time, the conductivities were improved with the increase of Sr2+ content. The thermoelectric properties of La1-xSrxCrO3 depended on the Sr2+ content and the average Seebeck coefficients had an exponential decay tendency with the increase of Sr2+ content. For La1-xSrxCrO3 (x = 0.1–0.4)-In2O3 thermocouples, excellent repeatability and stability were observed through multi-cycles and long-time usage testing at high temperature. The La0.7Sr0.3CrO3-In2O3 thick film thermocouple with excellent thermal stability (drift rate: 0.81 °C/h) and reliability makes it become a promising candidate high sensitivity thermal sensor.

Photoluminescence behavior on Sr2+ modified CaCu3Ti4O12 based ceramics

Sr2+ modified CaSrxCu3-xTi4O12ceramic powders with x = ranging from 0.00 to 3.00 were prepared by solid-state reaction. The effects of Sr2+ CCTO powders were evaluated by X-ray diffraction (XRD) with Rietveld refinement revealing a mixture of multiple phases. The Raman spectroscopy analysis pointed out that Sr2+ addition produces an emission in the blue region, associated to TiO6 clusters. Optical properties by means of PL analysis showed emission near to blue region for the samples with x = 0.00, x = 0.15, x = 0.30, corresponding to oxygen vacancies. The emission in the violet region is associated to deep defects while emission in the other samples is linked to shallow defects typical of disordered crystalline structures. Less prominent emission in the green region with the increase of Sr2+ corresponds to less self-trapped charges, less interaction between electron and hole, and donor–acceptor recombination.

Kinetics of Sr2+ sorption on clinoptilolite-containing tuffs of different deposits from the surface drinking water

Previously Sr2+ion-exchange isotherms were obtained from the surface drinking water and the corresponding Sr2+ distribution coefficients (Kd) were calculated for linear part of the isotherms of the studied CLT. The comparative kinetic data of Sr2+ ion-exchange sorption on NH4+- forms of the clinoptilolite-containing tuffs from deposits of Russia and Bulgaria on the sample of the surface drinking water was investigated in detail with the known method of the "thin layer". It was shown, that the kinetic process of the Sr-sorption on the clinoptilolite- containing tuffs is characterized with the features and includes 3 stages. The first stage is described with the particle diffusion law, the second stage –a slowing down, the ion-exchange process reaches a plateau, then an increase of Sr2+ sorption is observed again. The particle diffusion coefficients of Sr2+ describing the first stage of the sorption process on CLT of different deposits were calculated. The obtained data are the initial one for the development of a mathematical model of the dynamic ion-exchange process on NH4+-form of the clinoptilolite- containing tuffs from the surface drinking waters, that makes possible to generate the computer program and thereupon to calculate the break-through curves of Sr2+ sorption on NH4+- clinoptilolite- containing tuffs for the different dynamic conditions, including the sorption dynamic conditions on the permeable reactive barrier

Effects of strontium adding on the drug delivery behavior of silica nanoparticles synthesized by P123-assisted sol-gel method

In the present research, the effects of Sr2+ addition on the drug delivery behavior of nanoporous silica nanoparticles (NSNPs) synthesized by P123-assisted sol-gel were investigated. The XRD results showed that by adding Sr2+ to NSNPs, SrSi2O6H2 and Sr2Si2O9H6 phases were appeared. NSNPs had particle size of about 20 nm. With the increase of Sr2+ content in the NSNPs, the average particles size is significantly increased. The drug loading results exhibited that although NSNPs had higher surface area in comparison with strontium modified NSNPs samples, the latter particles had higher capacity for drug loading. The drug delivery results showed that with the increase of Sr2+ contents, the release rate reduced. A possible mechanism for drug delivery in this system was discussed.

Enhanced luminescence properties of double perovskite (Ba, Sr)LaMgSbO6:Eu3+ phosphors based on composition modulation

Eu3+-doped double perovskite (Ba, Sr)LaMgSbO6 phosphors were synthesized by the traditional solid-state reaction method. Structure evolution was investigated by X-ray diffraction and Rietveld structure refinement. The crystallographic data of powders were given in detail. Also, the photoluminescence properties, including excitation spectra, emission spectra, intensity ratios of I (5D0-7F2)/I (5D0-7F1), Commission International de L'Eclairage (CIE) chromaticity coordinates, UV–vis diffuse reflectance spectra, lifetimes, and the thermal quenching properties were thoroughly discussed. With the increase of Sr2+ concentration, the emission intensities increased and the decay times decreased. Band gap was calculated to explain the phenomenon of the increased emission intensity. The phosphors showed temperature-sensitive luminescent properties based on the thermal quenching performance. The configurational coordinate diagram was used to explain the thermal quenching mechanism.

Structural and Physical Properties Study of Some Phosphate Glasses Used for Radiation Shielding

Mossbauer Effect (ME) and Infrared (IR) spectroscopes are used to study the structure of some iron-sodium phosphate glasses containing strontium, with composition [(70-x) mol% P2O5. x mol% SrO, 15 mol% Fe2O3.15 mol% Na2O, where x= 3, 6,9,12 and 15]. These glasses can have many interesting applications especially as gamma ray attenuators.The amorphous nature and the glassy state character of these glasses can be confirmed from comparing the experimental and empirical values of both their density and molar volume. It was found that, as SrO was gradually increased the density increased while the molar volume decreased which may be due to the gradual decrease of the number of oxygen ion density in the glass networks.The micro-hardness and magnetic susceptibility are also increased, which can be attributed to the gradual migration of iron from glass network modifier (GNM) to glass network former (GNF) positions, as confirmed by IR and ME results. IR and ME analysis indicated that both ferric and ferrous have tetrahedral and octahedral symmetry respectively and acting as GNF and GNM at different SrO contents. The gradual replacement of P2O5 by SrO force the iron to transfer from GNM to GNF.The gamma-ray mass attenuation coefficient increased with the gradual increase of Sr2+ as heavy metal, while the HVL decreased. On the other hand the attenuation coefficient decreased with the increase of gamma-ray photon energy. So, these glasses can be used as transparent shielding materials for low gamma-ray energies and to capsulate the radio-active wastes, while the sample containing 15 mol% SrO, exhibits the highest attenuation coefficient. Â

Structural refinement, Raman spectroscopy, optical and electrical properties of (Ba1−xSrx)MoO4 ceramics

In this paper, structural refinement, Raman spectroscopy, optical and electrical properties of barium strontium molybdate [(Ba1−x Sr x )MoO4] ceramics with different (x) contents (x = 0; 0.1; 0.2; 0.3; 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; and 1) were synthesized by the solid state reaction method. These ceramics were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, and micro-Raman spectroscopy. The shape of the grains for these ceramics was observed by means of scanning electron microscopy (SEM) images. The optical properties were investigated using ultraviolet–visible (UV–Vis) absorption spectroscopy and photoluminescence (PL) measurements. The dielectric and ferroelectric properties were analyzed by permittivity (er), loss tangent (tan δ) and polarization versus electric field (P–E) hysteresis loop. XRD patterns, Rietveld refinement, and micro-Raman spectra showed that all ceramics are monophasic with a scheelite-type tetragonal structure. A decreased of lattice parameters and unit cell volume was observed with the increase of Sr2+ ions into BaMoO4 lattice. Rietveld data were employed to model the [BaO8], [SrO8] and [MoO4] clusters in the tetragonal lattices. The SEM images indicate that increased x content promotes a decrease in the grain size and modifications in the shape. UV–Vis spectra indicated a decrease in the optical band gap values with an increase in x content in the (Ba1−x Sr x )MoO4 ceramics. PL emissions exhibit a non-linear behavior to increase or decrease with the increase of Sr2+ ions in the tetragonal lattices, when excited by a wavelength of 350 nm. The P–E decreases along with slim hysteresis loop towards higher Sr2+ ions concentration. These effects are correlated with decrease in lattice parameters and c/a ratio in this tetragonal lattice. The microwave dielectric constant and quality factor were measured using the method proposed by Hakki–Coleman. Temperature coefficient and quality factor of these materials were measured by vector network analyzer.

The effect of Sr2+ on the structure and magnetic properties of nanocrystalline cobalt ferrite

We report the effect of Sr2+ on the structure, morphology and magnetic properties of CoFe2O4 synthesized by microwave-assisted combustion method. Results from X-ray diffraction and Mössbauer spectroscopy at 298K suggest the formation of a mixed spinel Sr2+ substituted CoFe2O4. However, secondary phases like CoO, SrCO3 and SrFeO2.96 were also observed. A decrease in the lattice parameter and particle size were observed with the addition of Sr2+. The crystallite size of ferrite phase ranged from 53 to 62nm. Magnetic studies showed a gradual decrease in the saturation magnetization and remanence with the increase of Sr2+ content, and an increasing value of the coercive field.