Tailoring the structural and optical properties of lead-free Na0.5(Bi1-xSmx)0.5TiO3 multifunctional ceramics by Sm-doping

• Published in: Journal of alloys and compounds Vol. 1005; p. 175963
• Main Authors: Volpi, F.M., Castro, T.J., Franco, A., Lira, S.O., Morais, P.C., da Silva, S.W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-11-2024
• Subjects: Diluted magnetic semiconductor; Nanoparticles; Room-temperature ferromagnetism; Sm-doped sodium bismuth titanate; Diluted magnetic semiconductor; Nanoparticles; Sm-doped sodium bismuth titanate; Room-temperature ferromagnetism
• DOI: 10.1016/j.jallcom.2024.175963
• ISSN: 0925-8388

In this study, the effects of Sm3+-content on the structural and optical properties of the Na0.5(Bi1-xSmx)0.5TiO3 multifunctional lead-free system were investigated using x-ray diffraction (XRD), ultraviolet-visible (UV-Vis), Raman spectroscopy and photoluminescence (PL) spectroscopy. The Na0.5(Bi1-xSmx)0.5TiO3 (x = 0.000, 0.005, 0.010, 0.015, and 0.020) ceramics were synthesized by the solid-state reaction method with subsequent annealing. The Rietveld method was used to refine the XRD data. The results of these refinements indicated that pure NBT (Na0.5Bi0.5TiO3) and the Sm3+-doped samples showed the coexistence of the rhombohedral (R3c) and tetragonal (P4bm) phases in different fractions, which depend on the Sm3+-content. The UV-Vis data revealed that the optical band gap of the Na0.5(Bi1-xSmx)0.5TiO3 samples monotonically decreases with increasing Sm3+-content, providing evidence of replacement of Bi3+- by Sm3+-ions. Furthermore, Raman spectroscopy confirmed that substitution of Bi3+- by Sm3+-ions leads to a shortening of the Na/Bi-O bond length. It was demonstrated that this behavior is responsible for the increase in the local symmetry of the TiO6 octahedron and the consequent decrease in the ratio between both rhombohedral and tetragonal phases, as observed by the XRD data. The findings from the PL data revealed typical emissions corresponding to transitions between the 4G5/2 → 6Hj (j = 5/2, 7/2, 9/2, 11/2, 13/2) states of the Sm3+-ion. Additionally, the presence of non-radiative recombination processes was found to depend on both laser pumping power and Sm3+-content.
•The Na0.5(Bi1-xSmx)0.5TiO3 ceramics were synthesized by the solid state method.•Unit cell volume, band gap and vibrational properties depend on the Sm3+-content.•The rhombohedral and tetragonal phases coexist and depend on the Sm3+-content.•The photoluminescence (PL) data were studied at increasing laser pump power.•Sm3+ PL-emissions are governed by Förster and Dexter energy transfer processes.