Papers by Keyword: Sr-Doped

Abstract: Perovskite La_1-xSr_xFe_0.7Ni_0.3O_3-δ with x = 0.0, 0.1 &0.2 denoted LSFN_x has been investigated as potential symmetrical electrode in solid fuel cells (SOFCs). The crystal structure is in pure orthorhombic phase for x = 0.0, orthorhombic-cubic phase coexist for x = 0.1 and pure cubic phase for x = 0.2. Structural properties are studied by X-ray powder diffraction (XRPD), refined by Rietveld analysis. SEM images show the morphology of as prepared and calcined samples either the compatibility between those electrodes and LSGM electrolyte in presence of 50% wt of Ce_0.8Gd_0.2O_2-δ, so that, lower chemical reactivity was found. Total conductivity, impedance in high, medium and low frequencies HF, MF and LF respectively, and resistance polarization (Rp) are determined in air. LaFe_0.7Ni_0.3O_3-δ has a good response in all ranges of frequencies but La_0.9Sr_0.1Fe_0.7Ni_0.3O_3-δ and La_0.8Sr_0.2Fe_0.7Ni_0.3O_3-δ have response only in HF and MF and exhibit Rp values as low as LaFe_0.7Ni_0.3O_3-δ .

Abstract: Strontium-modified lead zirconate titanate ceramics was prepared by the polymeric precursor method. The effect of Pb (II) substitution by Sr (II) in A site of the perovskite structure at molar percentages of 0.0, 0.2, 0.4 and 0.6 mol% was investigated through XRD and Rietveld method. The increasing of strontium amount displaces the morphotropic phase boundary toward to tetragonal phase and that results can be associated to the tetragonal lattice expansion besides the rhombohedral opposite phenomenon. The effect of strontium substitution on the dielectric properties for sintered ceramics is also investigated and showed the strontium substitution leads to reduction of weight loss and increasing of density for sintered ceramic. The Kc and Tc oscillates as function of ceramic morphology and is not possible to verify the existence of conductive intergrains defects by loss tangent curves. An intrinsic event can be occurring because considerable lattice distortion was verified in tetragonal and rhombohedral structures for powder samples.

Abstract: Perovskite type ferrite doped with Sr²⁺, Dy_1-xM_xFeO₃(x = 0.0, 0.05, 0.15, 0.25) were prepared by the conventional solid-state reaction. The structure and electromagnetic properties of the calcined samples were studied using powder X-ray diffraction (XRD, Rigaku D/Max-2500) and network analyzer (Agilent 8722ET). All the XRD patterns showed the single phase of the perovskite type ferrite without other intermediate phase when x≤0.25. The electromagnetic properties of the samples have been studied at the frequency range from 2 GHz to 18 GHz. The ε′ and ε′′ values were improved significantly. Both the values of ε′ and ε′′ increase with the increasing content of the doped cations Sr²⁺, and the peak value of ε′′ was about 2.2 at 12.1 GHz position when x = 0.25.

Abstract: In this paper, Sr-doped BaTiO3 based X7R ceramic was prepared. This material has dielectric constant of about 2000, temperature coefficients of capacitance (TCC) at 125°C of 11%, insulation resistivity of 12 × 1012 Ω⋅cm and grain size of 350 nm. The effects of Sr doping on the properties of the ceramics were also investigated.