Fluorophlogopite was stripped to a

Fluorophlogopite was stripped to a thickness of 100 μm to prepare the substrate. A high-temperature silver paste was used to print a thick film on the substrate (Fig. 1), followed by sintering at 800 °C for 15 min to prepare the bottom electrode. Then the BST thick films were prepared on the bottom electrode. The first layer of the BST film was dried in an oven at 100 °C for 30 s. The second layer was then printed on the first one and moderately dried; a total of four layers were printed. A 300-mesh silk screen (pore size: 8.47 μm) was used for the experiment. The distance between screen and substrate was approximately 0.7–1 cm, the scraper angle was 45°, and the speed ranged from 10 to 15 cm/s. After that, the thick films were annealed. The temperature was increased to 400 °C at a rate of 1 °C/min, and the samples were kept at 400 °C for 90 min. Then, the temperature was further increased to 950 °C at a rate of 3 °C/min, and the samples were sintered at 950 °C for 30 min. At last, A medium-temperature silver paste was used to print the upper electrode, and the printed electrode was sintered at 500 °C for 15 min.