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Bi-based Piezoelectric Thin Films via Chemical Solution Deposition

Bi-based Piezoelectric Thin Films via Chemical Solution Deposition

Wednesday, November 7, 2012 at 4:00 pm
Weniger 304
Prof. Brady Gibbons, OSU Materials Science
The highest performing piezoelectric materials include lead as a major constituent. Worldwide, increased restrictions on the use of lead have resulted in a search for candidates to replace these lead-based piezoelectric materials. One promising material is the solid solution of (Bi0.5Na0.5)TiO3 – (Bi0.5K0.5)TiO3 (BNT-BKT). Although promising behavior has been observed in bulk materials, similar results have been elusive for BNTBKT thin films. In this work, 0.8 BNT – 0.2 BKT thin films (near morphotropic phase boundary composition) were synthesized on platinized silicon substrates via chemical solution deposition. Well-crystallized BNT – BKT thin films were grown at varying processing conditions. Phase purity was confirmed by X-ray diffraction. As Bi, Na, and K are volatile elements, overdoping of these cations (addition of excess cation precursors) was introduced to compensate for volatilization during synthesis. Quantitative compositional analysis of films was performed with electron probe microanalysis and compositional depth profiling to confirm atomic ratios via X-ray photoelectron spectroscopy. The composition data from both measurements were consistent and indicated stoichiometric films were achieved. Dependent on the overdoping and annealing conditions, dense, smooth, crack-free films were achieved with relative dielectric constants from 390 to 730 and low dielectric loss of 2 - 5% at 1 kHz. Additionally, maximum and remanent polarizations of 45 and 16 μC/cm2, respectively, were recorded at 200 Hz. The addition of Bi(Mg0.5Ti0.5)O3 (BMgT) was also explored, as promising piezoelectric response in bulk compositions has been observed. BNT-BKT-BMgT thin films were prepared, showing very promising piezoelectric response with d33,f up to 90 pm/V and strain values of 0.35%.
Oksana