Synthesis of Bax(Bi0.5Na0.5)1−xTiO3 perovskite mesocrystals via a solvothermal topochemical process

Abstract

The Ba_x(Bi_0.5Na_0.5)_1−xTiO₃ (BBNT) perovskite is a promising lead-free piezoelectric material. In the present study, a two-step topochemical process was developed for the synthesis of BBNT mesocrystal particles with a plate-like morphology. In the first step, a layered titanate H_1.07Ti_1.73O₄·nH₂O (HTO) precursor was solvothermally treated in Ba(OH)₂ solution to obtain a BaTiO₃/HTO (BT/HTO) nanocomposite. In the second step, the BT/HTO nanocomposite was hydrothermally treated in a mixed BiCl₃–NaOH solution to obtain a BBNT mesocrystal. The formation, reaction mechanism, and nanostructure of the BBNT mesocrystal were studied by XRD, FE-SEM, TEM, and SAED. The plate-like BBNT mesocrystal was constructed from [110]-oriented BBNT nanocrystals with crystal sizes of about 30 nm. All BBNT nanocrystals in one plate-like BBNT mesocrystal showed the same orientation in the [110]-direction. The reactions for the formation of the BT/HTO nanocomposite from the HTO precursor and the BBNT mesocrystal from the BT/HTO nanocomposite were topochemical, which retained the plate-like morphology of the HTO precursor particle during synthesis. The BT nanocrystals in the BT/HTO nanocomposite acted as anchors that maintained the plate-like morphology during the formation of the BBNT mesocrystal.