Potassium sodium niobate based lead-free ceramic for high-frequency ultrasound transducer applications

摘要

The BiAlO_(3) (BA) and (Bi_(0.5)Na_(0.5))ZrO_(3) (BNZ) are selected to form a solid solution with (K_(0.48)Na_(0.52))NbO_(3) via traditional solid state technique to optimize the electrical performance and temperature stability of KNN-based lead-free ceramics, simultaneously. Here we show that doped BA has a great influence on phase structure, morphologies, and electrical properties. The XRD patterns and dielectric constant versus temperature curves reveal that an increase in the BA content results in a transform of phase structures from a coexistence state of rhombohedral, orthorhombic and tetragonal phases to pseudocubic phase. Owing to the construction of R-O-T phase boundary, optimized performances ( T _(C)?～?336?°C, d _(33) ～ 306?pC/N, k _(p)?=?0.48) are obtained in 0.962(K_(0.48)Na_(0.52))NbO_(3)-0.003BiAlO_(3)-0.035(Bi_(0.5)Na_(0.5))ZrO_(3) (KNN-3) ceramics. Based on the sintered KNN-3 ceramic samples, high-frequency ultrasound imaging transducers are designed and fabricated, which exhibits a high center frequency of 24.5?MHz, a broad??6 dB bandwidth of 97% and a high-sensitivity. Finally, the imaging characteristic of the lead-free transducers is demonstrated via ex?vivo imaging of biological tissue structure. As environment friendly materials, the excellent electrical and acoustic performance of developed KNN-based ceramics has great potential for practical applications.