Influence Of Sr Doping Research Articles

Influence of Sr doping on BaTiO3 properties: A combined DFT and experimental approach

Barium titanate (BaTiO3) has been extensively used as a compound due to its potential for optoelectronics and electronic applications. The density functional theory (DFT) calculations as well as chemically prepared thin films were used to investigate the effect of the alkaline earth metal Sr on the electronic, thermoelectric, structural, morphological, and optical properties of the BaTiO3 host matrix.It was found in band structure analysis that the bandgap nature changed from indirect to direct bandgap upon incorporation of the Sr atom into the BaTiO3 host lattice. Thermoelectric characteristics showed notable changes in response to temperature and doping. The investigation demonstrated that optimized electrical conductivity, reduced thermal conductivity, and an enhanced Seebeck coefficient were achieved with a precise (5.55 %) Sr content. XRD analysis revealed the cubic phase of the prepared thin films. Morphological investigation showed the evolution of grain with the increase in dopant contents. The theoretical and experimentally measured optical characteristics also revealed that Sr doping improved the material’s refractive index, conductivity, and absorption coefficient in the visible and ultraviolet energy ranges. Significant enhancements in electronic, thermoelectric, and optical properties suggest that doped BaTiO3 could be considered a potential applicant for optoelectronic as well as thermoelectric applications.

Influence of Sr doping on structural and electrical properties of ceria and performance of a single solid oxide fuel cell

Influence of Sr doping on structural and electrical properties of ceria and performance of a single solid oxide fuel cell

Influence of Sr-doping on the metal–insulator transition temperature and magnetoelectric properties of La0.67Ca0.33Mn0.98V0.02O3 polycrystalline ceramics

Influence of Sr-doping on the metal–insulator transition temperature and magnetoelectric properties of La0.67Ca0.33Mn0.98V0.02O3 polycrystalline ceramics

Influence of Sr doping on the photoelectronic properties of CsPbX3 (X = Cl, Br, or I): a DFT investigation.

To broaden the application of cesium lead halide perovskites, doping technology has been widely proposed. In this study, we calculated a 12.5% concentration of a Sr-doped CsPbX3 (X = Cl, Br, or I) perovskite via density functional theory. The results showed that the bandgap energy of the perovskite increased by 0.2-0.3 eV. The high symmetry points of the energy band changed from R to Γ after Sr doping because the Sr doping affected the initial distribution of atomic orbital hybridization. In addition, optical absorption spectra after doping showed an obvious blueshift, whereas the absorption coefficient of CsPb0.875Sr0.125X3 had the same magnitude as undoped CsPbX3. Moreover, the effective masses of electrons and holes changed within a small range (0.01-0.03 m0) after Sr doping. According to the findings of this study, the CsPb0.875Sr0.125X3 perovskite is expected to become an ideal candidate material for designing photovoltaic and photoelectric devices.

Influence of Sr-doping on structural, optical and photocatalytic properties of synthesized Ca3(PO4)2

Well-crystallized Ca3(PO4)2 doped and un-doped nano-particles with the maximum strontium content (40 wt% Sr) followed by calcination at 800 °C for 3 h were synthesized via facile co-precipitation method. DTA/TGA, X-ray diffraction (XRD), energy dispersive scanning electron microscopy (SEM/EDX), UV–vis diffuse reflectance spectrum (UV–vis DRS), Raman spectroscopy and photoluminescence (PL) techniques were used for material characterization. The (XRD) patterns of as-synthesized Sr-doped Ca3(PO4)2 solid solution samples exhibited a systematic shift toward lower angles by possessing a single rhombohedral crystal structure without any secondary phases. The UV light driven photocatalytic activity was assessed for rhodamine B (RhB) degradation. As a result, ultrafast photodegradation activity was observed after Sr doping. Moreover, the 30 wt% Sr-Ca3(PO4)2 sample showed the highest photocatalytic degradation among the Sr-doped Ca3(PO4)2 samples toward RhB. It was further suggested that as-synthesized 30 wt% Sr-Ca3(PO4)2 superior photocatalytic performance is ascribed to the more proficient partition of photogenerated electron-hole pairs. Furthermore, the involved mechanism of superior photocatalytic performance of the 30 wt% Sr-Ca3(PO4)2 solid solution was also investigated. In addition, regeneration cycles indicated the higher stability of the photocatalyst to be effectively recycled up to four times without any considerable reduction in photocatalytic performance. Thus, these informations further provides us a scalable pathway to fabricate Sr doped Ca3(PO4)2 and its consequent use as an efficient photocatalyst for rhodamine B (RhB) contaminated wastewater treatment.

Influence of Sr Doping on Magnetic and Magnetocaloric Properties of Nd0.6Sr0.4MnO3

Nd0.6Sr0.4MnO3 sample is fabricated by a solid-state reaction method and its magnetic, magnetocaloric properties are investigated. The Curie temperature, TC, at which a ferromagnetic-paramagnetic transition occurs is about 270 K. Based on an analysis using the Banejee’s criterion for the experiment results of magnetic-field dependences of magnetization and the universal curves of the normalized entropy change versus reduced temperature, we assess magnetic order existing in this sample. Furthermore, the maximum magnetic entropy change, which occurs near TC, measured at a magnetic field span of 50 kOe is about 6.0 J/kg.K corresponds to relative cooling power of 250 J/kg. These values are comparable to those of other manganites.

Enhanced room-temperature TCR of La0.67Ca0.33-xSrxMnO3 (0.06 ≤ x ≤ 0.11) polycrystalline ceramics by Sr content adjustment

Herein, the influence of Sr doping on chemical composition, microstructure, and electrical transport properties of La0.67Ca0.33-xSrxMnO3 (LCSMO, 0.06 ≤ x ≤ 0.11) polycrystalline ceramics is systematically investigated. The study was performed by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), elemental mapping, energy dispersive spectrometry (EDS), X-ray photoemission spectroscopy (XPS), and four-probe method (ρ-T). XRD results verified the synthesis of high-purity orthogonal perovskite structure with Pnma space group. EDS and XPS results confirmed presence and uniform distribution of La, Ca, Sr, Mn and O. Furthermore, ρ-T curves indicated that the resistivity decreased with increasing Sr content, whereas metal-insulator transition temperature (TMI) gradually increased. Moreover, cell volume (V) and electron bandwidth (W) increased with the increase in Sr content, which effectively reduced the resistivity of LCSMO ceramics. One should note that double exchange (DE) enhancement between Mn3+ and Mn4+ is responsible for gradually increasing TMI. Finally, maximum TCR value of 14.3% K−1 was achieved at x = 0.08, which rendered TCR peak temperature of 299.0 K. High room-temperature TCR of LCSMO ceramics is promising for next-generation infrared bolometers, operating at room-temperature.

Electronic structure and bonding interactions in Ba1−xSrxZr0.1Ti0.9O3 ceramics

An investigation on the precise electronic structure and bonding interactions has been carried out on Ba1−xSr x Zr0.1Ti0.9O3 (short for BSZT, x = 0, 0.05, 0.07 and 0.14) ceramic systems prepared via high-temperature solid state reaction technique. The influence of Sr doping on the BSZT structure has been examined by characterizing the prepared samples using PXRD, UV-visible spectrophotometry, SEM and EDS. Powder profile refinement of X-ray data confirms that all the synthesized samples have been crystallized in cubic perovskite structure with single phase. Charge density distribution of the BSZT systems has been completely analyzed by the maximum entropy method (MEM). Co-substitution of Sr at the Ba site and Zr at the Ti site into the BaTiO3 structure presents the ionic nature between Ba and O ions and the covalent nature between Ti and O ions, revealed from MEM calculations. Optical band gap values have been evaluated from UV-visible absorption spectra. Particles with irregular shapes and well defined grain boundaries are clearly visualized from SEM images. The phase purity of the prepared samples is further confirmed by EDS qualitative spectral analysis.

Electronic structure and chemical bonding in La1−xSrxMnO3 perovskite ceramics

This study reports on the synthesis of La1−xSrxMnO3 (x = 0.3, 0.4 and 0.5) manganites by high temperature solid state reaction method using lanthanum oxide, strontium carbonate and manganese oxide as starting materials. The synthesized samples were characterized by XRD, UV-vis, SEM/EDS and VSM. Structural characterization shows that all the prepared samples have the perovskite rhombohedral structure. Influence of Sr doping on electron density distributions in the lattice structure of LaMnO3 were analyzed through maximum entropy method (MEM). Cell parameters are found to be decreasing with the addition of Sr content. The qualitative and quantitative analysis by MEM reveals that, incorporation of Sr into LaMnO3 lattice enhances the ionic nature between La and O ions and decreases the covalent nature between Mn and O ions. Optical band gap values are determined from the UV–visible absorption spectra. Particles with polygonal form are observed from the SEM micrographs. The elemental compositions of the synthesized samples are confirmed by EDS. The magnetic properties studied from the M-H plot taken at room temperature indicated that, the prepared samples are exhibited ferromagnetic behavior.

Density functional theory calculations of atomic, electronic and thermodynamic properties of cubic LaCoO3and La1−xSrxCoO3surfaces

Spin-polarized DFT calculations were used to investigate the atomic, electronic structures of LaCoO3and La1−xSrxCoO3surfaces. The thermodynamic stability of these surfaces was analyzed with phase diagrams. Influence of Sr-doping was also examined.

Influence of Sr-doping on the photocatalytic activities of CdS–ZnS solid solution photocatalysts

Alkaline earth metal Sr was successfully doped into CdS–ZnS solid solutions for the first time. The as-prepared photocatalysts were characterized by X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface areas, UV–vis diffuse reflectance spectra (UV–vis), photoluminescence spectra (PL), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), etc. BET characterization indicated that all the prepared samples possessed mesoporous structures with large specific surface areas. Photocatalytic H 2 evolution results showed that Sr-doping can efficiently improve the photocatalytic activities while the molar ratio of Zn was greater than 20% in the absence of noble metal as co-catalyst. The correlation between the Zn/Cd ratio of solid solution and the Sr-doping amount was investigated in detail. Results showed that the recombination of photoelectrons and holes could be efficiently suppressed by doping metal ions on the shallow surface of CdS–ZnS, which could become the centers of shallow electrons or holes traps, thus significantly improve the efficiency of charge separation.

Influence of Sr doping on the second magnetization peak and the critical current density of YBa 2Cu 3O 7− δ single crystals

Magnetic hystheresis loops of a series of YBa 2− x Sr x Cu 3O 7− δ ( x=0.1, 0.25, 0.37 and 0.5) single crystals reveal a huge “peak effect” over a wide range of low temperatures. Previous magnetoresistivity and magnetic irreversibility measurements already have evidenced that the superconducting state of these samples has a granular character and that their magnetic irreversibility line crosses over from the high field flux-creep (fc) regime to low field regimes, characterized by the intergrain Josephson flux-dynamics in a frustrated superconducting-grain aggregate. The present work adds to this that the peak effect vanishes at the temperature limit where the crossover from the fc to the low field regimes takes place. This is a clear indication that the peak effect is entirely related to the intragrain Abrikosov flux-dynamics.

Influence of Sr-doping in Ba7Rh6O18, a new one-dimensional oxide of the homologous series (A3Rh2O6)alpha(A3Rh3O9)beta.

The synthesis and microstructural characterization, by means of selected-area electron diffraction and high-resolution electron microscopy, of Ba7Rh6O18 is reported. This material, isostructural to Ba7Co6O18, is formed by rows of one trigonal prism and five face-sharing octahedra running parallel to the c-axis of a trigonal unit cell with parameters a = 1.004(5) and c = 3.165(7) nm. The substitution of Sr by Ba is accommodated by means of twin formation due to a rearrangement of the rows of polyhedra.

On the role of nonstoichiometry on the photostimulated luminescence in Ba(1−x)SrxFBr:Eu

The influence of Sr-doping and changing the F/Br-ratio on the properties of the widely used X-ray storage phosphor BaFBr:Eu is investigated. It is confirmed that Sr-doping considerably increases sensitivity and it is shown that Sr gives rise to new stimulation bands at 1.92 and 2.28eV. In order to increase the phosphor performance for stimulation at 633nm a Sr concentration between 15–20% is most favorable. Further results indicate that for storage phosphors synthesized from BaBr2, SrBr2, BaF2 and SrF2 an F/Br-ratio of 107/93 seems to be most favorable for practical application.

Influence of Sr doping on the free carrier absorption in high-T c superconductors La2?x SrxCuO4

The reflectance spectra of polycrystalline La2−xSr x CuO4 samples were investigated in the energy range between 50 meV and 4 eV in dependence of the Sr content. The spectra are attributed to free carrier absorption of the Drude type, superimposed by optical phonon excitations below 0.1 eV and intrinsic absorption above 1 eV. From the influence of Sr doping onto the plasma energy it is deduced that La2−xSr x CuO4 is ap-type conductor with a maximum carrier concentration of 2.0×1021 cm−3 forx=0.15. The results are interpreted in terms of a Hubbard model with an empty upper and ap-doped lower Hubbard band with a width of 1.9 eV.