Influence of Bi Excess on the Structural and Morphological Properties of Bi_0.5K_0.5TiO₃ Synthesized by Using the Hydrothermal Method and Its Nanogenerator Properties

This study investigated the effects of an excess of bismuth in Bi_0.5K_0.5TiO₃ (BKT) on its structural and morphological properties. Two types of BKT samples were prepared using bismuth stoichiometry, where one with a Bi:K molar ratio of 1:1 (S-BKT) and the other with a ratio of 1.1:1 with 10 mol% excess of Bi (10% BKT). These samples were prepared using the hydrothermal synthesis method. When the X-ray diffraction (XRD) data for the two samples were compared, the 10% BKT shows a 1.3 times larger than that for the S-BKT sample in the ratio of the secondary phase peak to the BKT (101) peak at approximately 29.3°. Morphology analysis showed that both samples had agglomerations with diameters of approximately 200 nm and nanowires with lengths of 1–2 μm and diameters of 8 nm. The fractions of the total area occupied by agglomerations in the two samples were estimated at approximately 95% for 10% BKT and approximately 45% for S-BKT. These results indicate that an excess of bismuth affects the secondary phase and agglomeration formation. Nanogenerators were prepared by mixing S-BKT, and their output voltages were 1.8 V and their outputs currents were 4 nA.