An explicit and novel structure, lattice dynamics, and photoemission of La-doped nanocrystalline SrZrO 3 perovskit
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Rare Met. https://doi.org/10.1007/s12598-019-01326-y
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An explicit and novel structure, lattice dynamics, and photoemission of La-doped nanocrystalline SrZrO3 perovskite Kamilia Sedeek, Nahed Makram, Hanan Hantour, Taghreed Zaghloul Amer, Shimaa Ali Said*
Received: 22 November 2018 / Revised: 12 February 2019 / Accepted: 20 August 2019 Ó The Nonferrous Metals Society of China and Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract As no complete and comprehensive studies have been previously reported for La-doped nanocrystalline SrZrO3 (SZO), we researched herein a detailed investigation for pure and La-doped samples. A modified solid-state reaction process, including successive cycles of milling and sintering at high temperature, was followed to produce SZO and Sr0.9La0.1ZrO3 (SLZO) powdered ingots. Rietveld analysis of X-ray diffractometer data predicts that the two samples exhibit orthorhombic structure with an increase in crystallite size by *25% for doped sample. A great reduction in Raman modes intensity (*60%) and an annihilation of several vibration modes were detected using Raman spectroscopy. The degree of ordering on the B-site was recorded to be higher in La-doped sample. According to ultraviolet–visible (UV–Vis) absorption, a decrease in the optical gap width (Eg) from 4.40 eV to 4.21 eV was achieved by La incorporation due to the presence of additional defect states such as oxygen and Sr vacancies at the band edge. The process of electron–hole recombination was studied using photoluminescence (PL) spectroscopy. Deconvolution of PL spectra yielded four emission bands: one green band, one blue band, and two violet bands. Highly intense violet emission at k = 393 nm approximately five times greater than that detected for pure SZO is realized as La3? substitutes for Sr2?. Such property nominates SLZO for technological applications requiring highly intense violet emission, e.g., light-emitting diodes. K. Sedeek, N. Makram, H. Hantour, Sh. A. Said* Nano-Materials Laboratory, Physics Department, Faculty of Science, Al-Azhar University, Nasr City, Cairo 11751, Egypt e-mail: [email protected] T. Z. Amer Physics Department, Faculty of Science, Al-Azhar University, Nasr City, Cairo 11751, Egypt
Keywords Orthorhombic perovskite structure; Lattice dynamics; Diffused reflectance; Photoluminescence; Highly intense violet emission
1 Introduction SrZrO3 (SZO) belongs to the perovskite family with the general formula A2?B4?O3 [1, 2]. SZO is stable in orthorhombic phase with Pnma symmetry. It exhibits important physical properties such as high melting point ([ 2600 °C) and proton conductivity at high temperatures, which nominates it to be used in electrochemical devices for solid oxide fuel cells (SOFCs) [3, 4]. La is a proper donor dopant at the A-site in the SrZrO3 perovskite due to its similar ionic radius. La is expected to give one delocalized electron doped for every atomic substitution of Sr. SrTiO3 doped with La has been attracted significant attention due to
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