Phase transformation, nanorod-like morphology, wide bandgap, and dielectric properties of 1-x (Al_(0.2)La_(0.8)TiO_3) + ⅹ (BaTiO_3) (x= 0.2-0.8) nanocomposites

摘要

A series of 1 - ⅹ (Al_(0.2)La_(0.8)TiO_3)+x (BaTiO_3) (x = 0.2, 0.4, 0.6, and 0.8)/ALTBT nanocomposites were prepared via the hydrothermal technique at 150 °C/6 h. The phase identification and structural transformation from tetragonal to cubic were confirmed using the X-ray diffraction pattern (XRD). Particularly, the low BaTiO_3 contents (x = 0.2 and 0.4) revealed the tetragonal structure, while the high BaTiO_3 contents (x = 0.6 and 0.8) showed the predominant cubic phases. Furthermore, the nanorod-like surface morphology was evidenced from the field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The optical properties ensured the presence of metal oxide (M-O) bonds and wide optical bandgap (E_g～3.975-3.899 eV) values. The frequency dependence of dielectric properties was described as a function of composition. The results expressed that the high dielectric constant (ε') of 260.8 was noticed at 10 kHz for ⅹ = 0.8 composite. The dc-electrical conductivity (σ_(dc)) and exponent (n) parameters were determined by applying power law fit to the log σ_(ac) versus log ω plots. The temperature dependence of dielectric constant plots indicated the dielectric transition temperature from 723 to 623 K with the increase of V.