Abstract
The different Na contents (0 ≤ Na ≤ 0.35, based on mole of NaOH) of doped Ba0.5Sr0.5TiO3(BST) powders synthesized via sol-gel process were studied. The substitution of Na+ions into a partial A-site of BST powders provided the reduction in vacancy defects as confirmed by electron paramagnetic resonance (EPR) and UV-visible spectroscopy. Photoluminescence (PL) spectra appeared in violet, blue, and green emissions. The phase structure, oxygen deficiency, and titanium deficiency of BST powders were further investigated as a function of Na content. X-ray diffraction (XRD) result was found that low Na content (0 ≤ Na ≤ 0.15) exhibited the tetragonal structure, while it was transformed to the cubic phase when high Na content. Moreover, X-ray photoelectron spectroscopy (XPS) result revealed that the partial oxidation of Ti3+ions to Ti4+ions was observed at Na content lower than 0.05 mole, while more addition of Na content resulted in the increasing of the oxygen and the titanium deficiency. Furthermore, the result indicated the oxygen deficiency significantly formed at the A-site of Sr atoms more than that of Ba atoms.
Highlights
The Na-doped BST powders were characterized by thermogravimetric analyzer (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), PL, ultraviolet-visible spectroscopy (UV-vis), and electron paramagnetic resonance (EPR)
At high Na content, that is, BST0.25 and BST0.35, the Na+ ions were randomly occupied into the A-site of BST powders and the BO6 octahedral distortion was decreased
The five peaks of PL spectra were found to be at 3.15, 2.95, 2.80, 2.55, and 2.33 eV. These can be assigned to the band gap, the fully ionized oxygen vacancy singly ionized oxygen vacancy
Summary
The Ba0.5Sr0.5TiO3 (BST) powders exhibit excellent electrical properties and have been extensively used in various electronic applications such as semiconductor, dynamic random access memory (DRAM), ceramic capacitors, pyroelectric sensors, and microwave devices [1, 2]. The metal doped perovskite materials can substitute into A- and/or B-site, relying on the ionic radii of metal dopant. The oxygen vacancy is a kind of anion vacancy that can be generated as well as the recombination of electrons and holes defect [12]. It plays an important role in the structurally order-disorder of perovskite materials [13]. It was found that the oxygen deficiency significantly affected the A-site of Sr atoms more than that of Ba atoms and the modified A/B-site of BST powders influenced the phase structure [3]. The Na-doped BST powders were characterized by TG, XRD, XPS, PL, UV-vis, and EPR
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