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The crystal structure, morphology, and linear and nonlinear optical properties of Co-doped Ba1−xCoxTiO3 (x = 0.00, 0.02, 0.03, 0.04, and 0.06) were investigated using x-ray diffraction (XRD), scanning electron microscopy, and UV–visible spectroscopy measurements. The XRD patterns confirmed that the Ba1−xCoxTiO3 samples crystallized in the perovskite phase, and a transition from quadratic to pseudo-cubic phase was observed with Co doping. Upon doping, the band gap (Eg) decreased from 3.14 eV to 2.11 eV, indicating that Co doping into BaTiO3 caused a change in their electronic levels associated with lattice defects. Additionally, the optical parameters including linear refractive index, extinction coefficient, dielectric coefficient, optical conductivity (σopt), and the static index (n0) were extracted and linked to the Co content. Finally, analysis of the linear (LOp) and nonlinear optical (NLOp) parameters of Ba1−xCoxTiO3 revealed that the increase in Co content induces an increase in the NLOp refractive index (n2) and third-order NLOp susceptibility χ(3). [ABSTRACT FROM AUTHOR]

As a lead-free ceramic, lanthanum-modified barium titanate (BLT) has attracted significant attention among researchers in recent years due to its interesting ferroelectric and piezoelectric properties and insulating behavior, which can be improved by the doping effect. For that, (Ba0.7La0.3) (Ti1−xNix)O3 (where x = 0%, 1%, 3%, 5%, 7% or 10%), denoted as BLTNx, were synthesized via the sol-gel process. The effect of the divalent ion Ni2+ on the structural, microstructural and dielectric properties was investigated by x-ray diffraction (XRD) and Fourier transform infrared (FTIR), Raman, and impedance spectroscopy (IS). Surface morphology analysis is done by scanning electronic microscopy (SEM). Dielectric properties were determined in the ranges 28°C to 400°C and 1 kHz to 2 MHz. The results showed that a low doping amount of Ni (x < 5%) increases the dielectric constant. The sample with x = 5% exhibited, at 400°C, a relatively high dielectric constant (ɛ′ = 2202), the sample with x = 3% exhibited, at 100°C, low dielectric loss (tan(δ) = 0.009), and high insulating character, indicating a suitable material for multilayer ceramic capacitors (MLCCs) and energy storage. [ABSTRACT FROM AUTHOR]