Synthesis and properties of layered perovskite-like compounds PbBi2Nb2O9 and PbBi3Ti2NbO12

Abstract

Two lead-containing compounds of the Aurivillus family: PbBi2Nb2O9 and PbBi3Ti2NbO12 were synthesized using a conventional high-temperature solid-state (ss) method and ion-exchange (ie) method. The phase and chemical purity of synthesized compounds were confirmed by XRD and EDX, respectively. The second harmonic generation experiment confirmed that all synthesized compounds have a non-centrosymmetric crystal structure. Rietveld refinement of samples prepared by different methods confirmed that ion-exchange and solid-state products share the same crystal structures; however, indirect evidence for different distributions of Pb/Bi between crystallographic positions was observed. Phase transitions, corresponding to the Curie temperatures were detected using high-temperature XRD. Thermal expansion of ion-exchange reaction products was studied in the temperature range of 298–1273 K. The optical band gap, electronegativity, valence band (EVB), and conduction band (ECB) potentials of materials were calculated from UV–vis spectroscopy data. Both PbBi2Nb2O9 (ss) and PbBi2Nb2O9 (ie) can be used for the decomposition of organic molecules under visible light, while PbBi3Ti2NbO12 (ss) and PbBi3Ti2NbO12 (ie) can work only under UV light irradiation due to their wider band gaps.