Infotech Oulu Lecture Series
Advances in pb-free piezoelectric ceramics and transducers
Lecturer: Ahmad Safari, The Glen Howatt Electroceramic Laboratory, Department of Materials Science and Engineering, Rutgers, the State University of New Jersey, Piscataway, USA
Date: May 22, 2014
Time: 13:15 - 14:00
In this talk, the recent advances in processing and electromechanical properties of bulk ceramics, and acoustic properties of transducers of Pb-Free materials with BNT based compositions are reviewed.
The processing and electrocmechanical properties doped 0.88[Bi0.5Na0.5TiO3]-0.08[Bi0.5K0.5TiO3]-0.04[Bi0.5Li0.5TiO3] (abbreviated to BNKLT88) and 0.88[Bi0.5Na0.5TiO3]-0.08[Bi0.5K0.5TiO3]-0.04[BaTiO3] doped with Mn, Fe, and Sn ceramics were comprehensively studied. Different amounts of Mn and Fe were added to the BNKLT88 ceramics either in form of a dopant (B-site substitution) or an additive. Mn-addition led to a remarkable increase in the dielectric loss. On the other hand, Mn and Fe-doping in the Perovskite B-site resulted in a considerable enhancement of Qm as well as decreasing the planar coupling coefficient, dielectric constant, and dielectric loss. The performance of Mn-doped ceramics under high vibration velocity was evaluated by a high power measurement system. It was shown that Mn-doping effectively reduced the heat generation under high drive condition and resulted in a higher vibration velocity compared to the undoped samples.
The SnO doping of the barium site in BNT-BKT-BT sintered in air resulted in an improved coupling coefficient with increasing amounts of Sn. The dielectric properties of the compositions in which SnO was added were enhanced when sintered in flowing N2.
A single element ultrasonic transducer with the BNKBT88 and BNKLT88 (pure and Mn doped) ceramic as the active element was designed and fabricated. The ceramic was sandwiched between an epoxy-tungsten backing layer and a silver epoxy matching layer. An epoxy lens was also incorporated into the transducer’s design to focus the ultrasound beam. The focused transducer with a center frequency of about 25 MHz demonstrated a -6dB bandwidth of 55-68%, an insertion loss of -32 dB, and the -20dB pulsed length was about 150 ns. The performance of transducer is comparable with those of PZT.
More information: Jari Juuti
Last updated: 20.5.2014