Structural, optical, mechanical, and electronic properties of Cr-doped alumina
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Structural, optical, mechanical, and electronic properties of Cr-doped alumina Z. K. Heiba1 · Mohamed Bakr Mohamed1,2 · Adel Maher Wahba3 Received: 18 May 2020 / Revised: 13 July 2020 / Accepted: 15 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Cr-doped α-Al2O3 samples (Al2−xCrxO3, 0 ≤ x ≤ 0.25; step 0.05) were synthesized by citrate-precursor autocombustion method. The lattice parameters, bond distortion index, crystallite size, and lattice microstrain of the developed system were investigated using Rietveld profile method. The porous nature of the formed samples was elucidated by a scanning electron microscope. The effect of doping on the vibrational band positions was examined using Fourier-transform infrared technique. The photoluminescence emission showed that a red color was mainly exhibited by all samples, while that with x = 0.05 showed the highest intensity. Other colors appear with a small intensity for higher Cr-doped samples. The electronic, optical, and mechanical stability properties of undoped and doped samples were investigated using density-functional theory calculation.
1 Introduction Due to their outstanding characteristics, inorganic luminescent materials are extensively used in different applications including light-emitting display technologies, solar cells, and biomedical imaging [1]. Aluminum oxide is a well-known dielectric material featured by wide bandgap energy. It is also characterized by many polymorphic structures including gamma, delta, theta, and alpha; each could be produced through controlling annealing temperature [2]. Being practically superior, corundum phase of alumina, α-Al2O3 (also known as sapphire) has a wide variety of technological applications for its perfectly colorless, microwave transparency, mechanical properties, refractoriness, chemical stability at high temperatures, and wide bandgap dielectric material; Eg = 9.4 eV [3], due to the presence of several defects-related sub-energy levels in the bandgap [4]. The oxygen ( O2−) ions establish an almost close-packed hexagonal structure with two-thirds of the octahedral interstices * Mohamed Bakr Mohamed [email protected] 1
Physics Department, Faculty of Science, Ain Shams University, Cairo, Egypt
2
Physics Department, Faculty of Science, Taibah University, Al‑Madinah Al‑Munawara, Medina, Saudi Arabia
3
Department of Engineering Physics and Mathematics, Faculty of Engineering, Tanta University, Tanta, Egypt
filled with Al3+ ions [5]. The lattice of α-Al2O3 −has a trigonal Bravais configuration with a space group R 3 c , and the hexagonal unit cell includes six formula units [6]. On the other hand, doping α-Al2O3 with transition metal ions, such as Cr3+, Fe3+, Ti4+, … etc. can modify its physical, electronic, chemical, and/or optical behaviors [7]. Heiba et al. [8] reported that Fe-doped α-Al2O3 nanoparticles emit blue, red, violet colors which suggest their use in different potential applications such as ceramic nanopigments. Lin [9] proved that the hydro
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