D max 2600 pc

X-ray diffraction (XRD) utilized a Rigaku DMax-2600 PC (Japan) diffractometer of 2θ range 10–90 by a CuKα source of wavelength, λ = 1.5406 Å. Scanning electron microscopy (SEM) images were obtained on Hitachi Su-70, and transmission electron microscope (TEM) images, high-resolution TEM (HRTEM) and energy dispersive X-ray spectroscopy (EDS) were performed by a FEI Tecnai G2 F20 TEM with an accelerator voltage of 200 kV. The TEM sample was prepared by dropping a diluted suspension in ethanol on a Cu grid supported by carbon film. UV-vis spectroscopy was operated on a Shimadzu UV-2600 spectrometer to monitor the reduction of 4-NP. X-ray photoelectron spectroscopy (XPS) was acquired on an AXIS Ultra DLD using monochromatic Al Kα radiation.

Ba_0.7Sr_0.3TiO₃ (BST) and Ba_0.7Sr_0.295Pr_0.005TiO₃ (BST:Pr³⁺) nanoparticles were synthesized by a hydrothermal method. Firstly, 40 ml aqueous solution of strontium nitrates and barium nitrates (1.119375 mol L⁻¹, 99%, Aladdin) and praseodymium nitrates (0.005625 mol L⁻¹, 99%, Aladdin) were mixed with 23 ml ethanol solution of tetrabutyl titanate (1.25 mol L⁻¹, 99%, Aladdin). The pH value of the mixed solution was adjusted to be 13.5 by adding NaOH. The reactive solution was then sealed in a Teflon autoclave at 200 °C for 48 h. After cooling down to room temperature, the obtained product was thoroughly washed by deionized water and ethanol, eventually dried overnight in air.
The crystallization nature and morphology of the samples were characterized using powder X-ray diffraction (Rigaku D/MAX-2600/PC with Cu Kα radiation) and scanning electron microscopy (SEM; JEOL 6700F). Photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the samples were measured using a spectrofluorometer (HORIBA, Fluoromax-4). The polarization vs. electric field (P–E) hysteresis loop was obtained at 50 Hz using a Precision Premier II tester (Radiant Technology USA) at room temperature (30 kV cm⁻¹).