Development of Lead-free Piezoelectric Ceramic Resonators for High-frequency Oscillator Applications

Download or read book Development of Lead-free Piezoelectric Ceramic Resonators for High-frequency Oscillator Applications written by Ho-yan Wong and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Because of the good piezoelectric properties and low sintering temperature, CBT-Cu/Ba-0.30 and MBT-Cu/Ba-0.40 have been used to fabricate high-frequency double-layered ceramic resonators. The resonator has a pair of top and bottom electrodes and an inner electrode in between them; all of them are of the same dimensions (2 mm and 3 mm in diameter) and smaller than the lateral dimension of the resonator (~5.4mm {604} 4.5 mm). As the sintering temperature for CBT-Cu/Ba-0.30 and MBT-Cu/Ba-0.40 are below 1000°C, Ag70/Pd30 inner electrode, instead of Pt, can be used for cofiring with the ceramics, and hence there is a great saving in the production cost. Our results reveal that the spurious vibrations of the resonators have been successfully suppressed. This should be party due to the smaller electrodes which is one of the typical approaches in the energy trapping technique to confine the vibrations in the electroded region and hence to reduce the standing waves formed by the reflected waves from the sample edge. This should also partly due to the second harmonic thickness extension mode vibrations. Our results also reveal that although the MBT-Cu/Ba-0.4 ceramic has better piezoelectric properties, its performance as a resonator is not as good as CBT-Cu/Ba-0.30. For the CBT-Cu/Ba-0.30 double-layered resonator, it has a relatively "clean" resonance response and a lower temperature coefficient of frequency (TCF =-39.3 ppm/°C). It also has a relatively low impedance at resonance (14 and 30] for 3-mm and 2-mm electrodes, respectively), which is very close to the value for a commercially available PZT resonator. These suggest that the CBT-Cu/Ba-0.30 lead-free double-layered resonators have good potential to replace the lead-based resonators.