Dielectric, Piezoelectric, and Vibration Properties of the LiF-Doped (Ba 0.95 Ca 0.05 )(Ti 0.93 Sn 0.07 )O₃ Lead-Free Piezoceramic Sheets

• Published in: Materials 2018-01, Vol.11 (2), p.182
• Main Authors: Cheng, Chien-Min, Chen, Kai-Huang, Lee, Da-Huei, Jong, Fuh-Cheng, Chen, Mei-Li, Chang, Jhih-Kai
• Format: Article
• Language: English
• Subjects: Coupling coefficients; Curie temperature; Dielectric loss; Dielectric properties; Electron microscopes; Energy harvesting; Lead free; Lithium; Lithium fluoride; Piezoelectricity; Sheets; Sintering; Vibration; X-ray diffraction
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma11020182

By the conventional solid state reaction method, a small amount of lithium fluoride (LiF) was used as the sintering promoter to improve the sintering and piezoelectric characteristics of (Ba Ca )(Ti Sn )O₃ (BCTS) lead-free piezoceramic sheets. Using X-ray diffraction (XRD) and a scanning electron microscope (SEM), the inferences of the crystalline and surface microstructures were obtained and analyzed. Then, the impedance analyzer and d -meter were used to measure the dielectric and piezoelectric characteristics. In this study, the optimum sintering temperature of the BCTS sheets decreased from 1450 °C to 1390 °C due to LiF doping. For the 0.07 wt % LiF-doped BCTS sheets sintered at 1390 °C, the piezoelectric constant (d ) is 413 pC/N, the electric-mechanical coupling coefficient (k ) is 47.5%, the dielectric loss (tan δ) is 3.9%, and the dielectric constant (ε ) is 8100, which are all close to or even better than that of the pure undoped BCTS ceramics. The Curie temperature also improved, from 85 °C for pure BCTS to 140 °C for BCTS-0.07 LiF sheets. Furthermore, by using the vibration system and fixing 1.5 g tip mass at the end of the sheets, as the vibration frequency is 20 Hz, the proposed piezoelectric ceramic sheets also reveal a good energy harvesting performance at the maximum output peak voltage of 4.6 V, which is large enough and can be applied in modern low-power electronic products.