Tuning the dielectric properties of PbNb2O6 perovskite through calcium substitution

Environment-friendly lead-free perovskites have gained immense interest in the scientific community now a days. Here, we report the synthesis of PbNb2O6 using the sol-gel auto-combustion method, where Pb is substituted with Ca, which reduced its toxicity and improved its energy storage capacity. XRD analysis confirmed the formation of a rhombohedral phase for parent composition which transformed to the orthorhombic phase when Pb is completely replaced by Ca. Depending on the relative concentrations of Pb and Ca, the intermediate compositions exhibited dual phases. The crystallite size of all the compositions is in the range of 26-53 nm. Platelet-like morphology, besides particle agglomeration, has been observed for Ca-free composition. However, as the Ca concentration increased, a rod-like morphology appeared with a significant reduction in particle size. The presence of all elements according to their stoichiometric compositions is confirmed by energy dispersive X-ray spectroscopy. The presence of all downward peaks in the FTIR spectra in the range of 400-1000 cm(-1) are associated with the stretching and bending of Nb-O bonds, except for one peak which appeared at 432.13 cm(-1) and originates from the Pb-O bond. Dielectric analysis revealed that Ca substitution improved the dielectric constant of PbNb2O6 over wide frequency range. Even a frequency of 1 MHz, the value of dielectric constant is remarkably high with a small value of tangent loss. These properties demonstrate the potential of Pb-free perovskites for energy storage applications.

Automated summary

Environment-friendly lead-free perovskites have attracted great interest in the scientific community. The synthesis of PbNb2O6 using the sol-gel auto-combustion method was reported, with Ca substituting Pb to reduce toxicity and improve energy storage capacity. XRD analysis confirmed the transformation of the composition from a rhombohedral phase to an orthorhombic phase with complete replacement of Pb by Ca. The presence of dual phases was observed depending on the relative concentrations of Pb and Ca. The crystallite size ranged from 26-53 nm. Platelet-like morphology was observed in Ca-free composition, while rod-like morphology appeared with increasing Ca concentration. Dielectric analysis showed that Ca substitution enhanced the dielectric constant of PbNb2O6 over a wide frequency range.