Improved room temperature dielectric properties of Gd3+ and Nb5+ co-doped Barium Titanate ceramics

In this paper, we report the synthesis of gadolinium (Gd) and niobium (Nb) co-doped barium titanate (BT) ceramic oxides prepared using a conventional solid-state reaction method. The X-ray diffraction pattern confirmed the formation of tetragonal phase – with the space group P4mm – in all samples. X-ray photoelectron spectroscopy shows the formation of oxygen vacancies with a variable concentration that depends on the site preference of Gd ions. Fourier – Transform infrared analysis shows the presence of the most prominent peak between 544 cm−1 and 588 cm−1. Raman spectroscopy shows the tetragonal phase, with a most prominent peak around 514 cm−1 due to A1(TO3)E(TO4) mode. Shifting of this peak suggests the formation of GdBa defects. UV measurement suggests an increase in bandgap from 2.928 eV to 3.047 eV with Gd doping. Photoluminescence shows the presence of multiple level emission mechanisms for all samples. The dielectric constant increases while dielectric loss decreased with increasing dopant concentration, which is attributed to the self-compensation mechanism and defect dipole formation. Impedance spectra, Z′and Z′′vs frequency, suggest the presence of space charge polarization. Modulus spectra, M′and M′′vs frequency indicates the presence of short-range mobility at low frequency and long-range mobility at high frequency. AC conductivity shows almost negligible change with variable dopants concentration. Thus, electrical properties were observed to improve with Gd and Nb co-doping on BT ceramic oxides.