The investigation of structural and vibrational properties and optical behavior of Ti-doped La0.67Ba0.25Ca0.08Mn(1−x)TixO3 (x = 0.00, 0.05 and 0.10) manganites

Abstract

The influence of Ti⁴⁺ ions incorporated into the B site on the structural, vibrational and optical properties of La_0.67Ba_0.25Ca_0.08Mn_(1−x)Ti_xO₃ (LBCM_(1−x)T_x), a polycrystalline compound prepared by a molten salt method, was discussed. The X-ray diffraction (XRD) studies confirmed that at room temperature these compounds crystallize in the rhombohedral phases of Rc. Rietveld refinement indicated that the octahedron (Mn/Ti)O₆ underwent a slight deformation and the θ_{(Mn/Ti)–O–(Mn/Ti)} bond angles decreased with the increase in the Ti content. Furthermore, Raman spectra were recorded at room temperature for the LBCM_(1−x)T_x ceramics to investigate the influence of incorporated Ti⁴⁺ ions in LBCM_(1−x)T_x. Moreover, we controlled the frequency and damping of the optic modes based on Ti incorporation. The infrared (IR) absorption spectrum (FTIR) analysis in the span of 420–750 cm⁻¹ supports the XRD results. The diffuse reflectance data at room temperature verified that both transition levels (⁵E_g → ⁵T_5g) and (⁴A_2g → ⁴T_2g) correspond to the Mn³⁺ and Mn⁴⁺ ions. The optical band gap (E_g) values decreased from 2.90 eV to 2.70 eV with the increase in the Ti⁴⁺ content, implying that our samples could be good candidates for some applications in luminescent devices, such as ultrafast optoelectronic devices. Moreover, the photoluminescence spectra (PL) features at room temperature decreased for all samples. CIE were estimated for all the concentrations of Ti⁴⁺ ions. The results indicated that are a shifts in the CIE values of the compounds.