2020 Volume 128 Issue 8 Pages 475-480
A-site substituted (Ba1−x,Srx)TiO3 nanocubes (BSxT NC; x is Sr ratio) were synthesized by hydrothermal process with surfactant and additives. X-ray diffraction profiles of BSxT NCs showed single-phase of perovskite. Size of BSxT NCs was decreased with increasing Sr content under same hydrothermal condition. When synthesis temperature increased, size of BSxT NCs was enlarged. It revealed that the size of BSxT NCs was able to be controlled by optimizing the hydrothermal conditions. However, inhomogeneous substitution was observed by scanning transmission electron microscopy with energy dispersive X-ray spectroscopy. It suggested that reaction rate of Sr ions to form perovskite structure was faster than that of Ba ions under hydrothermal condition. Three-dimensional (3D) assemblies of BSxT NCs after heat-treatment at 850 °C had obscured interfaces between the NCs. Raman spectroscopy of NC assemblies revealed that symmetry of BSxT NCs differed from that of BaTiO3 (BT) NCs and did not change after heat-treatment at 850 °C. Piezoresponse curves became slim hysteresis behavior with increasing Sr ratio. These results suggested that Sr substitution of BT NCs caused phase transition from ferroelectric to paraelectric phase in 3D assemblies.