Effect of Pyrolysis Temperature on K_(0.5)Na_(0.5)NbO_3 Thick Films Derived from Polyvinylpyrrolidone-Modified Chemical Solution

摘要

Lead-free ferroelectric K_(0.5)Na_(0.5)NbO_3 (KNN) thick films with improved performances have been successfully prepared by poly-vinylpyrrolidone-modified chemical solution deposition method. The KNN thick films were obtained by pyrolyzing at different temperatures and annealing at 600℃. The effect of pyrolysis temperature on structures and electrical properties of KNN thick films is studied. The crystallinity of KNN films decreased with the increasing of the pyrolysis temperature, and the porous morphology is observed in the KNN films pyrolyzed at 480℃. However, the film pyrolyzed at 330℃ is dense. With the analysis of X-ray photoelectron spectroscopy for K ions, it was found that a low pyrolysis temperature favors the formation of per-ovskite KNN phase. Therefore, the electrical properties of the KNN films became improved at the low pyrolysis temperature. The KNN film pyrolyzed at 330℃ and annealed at 600℃ exhibits the large dielectric constant of 68S and low dielectric loss of 6.95%. The film also shows the saturated and symmetric polarization-electric field (P-E) loops with remnant polarization of 12 μC/cm~2 and piezoelectric coefficient d_(33) of 56 pm/V.