23 May 2003 Apodization process of piezoelectric ceramics for ultrasound transducers
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The objective of this work was to optimize the process of apodization of piezoelectric ceramic discs, looking for the better relationship between oil bath temperature and time of electrical field application. The apodization was performed to reduce the diffraction in the acoustic field generated by ultrasonic transducers. We used 12.7mm diameter and 1mm thickness PZT-5A discs. The apodization field (2kV/mm thickness) has been shaped by a 5mm radius spherical electrode throughout the apodization processes we have used. The apodized ceramic discs which showed electromechanical coupling coefficient value, for the thickness mode of vibration, equal or larger than 0.37, were considered well apodized. We used initial oil bath temperatures from 120°C to 250°C and the electric field was applied for periods of at least 2 minutes to up to 4 hours. The results showed that if the poling electric field was applied to the piezoelectric ceramic even before the oil was heated, we obtained larger piezoelectric coupling coefficients; in higher temperatures (250°C) this was not necessary. We concluded that using higher temperatures (250°C) it was possible to reduce the apodization process, with satisfactory results, from 4-5 hours to 2 minutes. Ultrasound transducers were built with apodized ceramics and their acoustic fields showed larger depth of field relative to non apodized ones.
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Mauricio Gomes Duarte, Mauricio Gomes Duarte, Vera Lucia da Silveira Nantes Button, Vera Lucia da Silveira Nantes Button, Joaquim Miguel Maia, Joaquim Miguel Maia, Eduardo Tavares Costa, Eduardo Tavares Costa, Eduardo Jorge Valadares Oliveira, Eduardo Jorge Valadares Oliveira, } "Apodization process of piezoelectric ceramics for ultrasound transducers", Proc. SPIE 5035, Medical Imaging 2003: Ultrasonic Imaging and Signal Processing, (23 May 2003); doi: 10.1117/12.479921; https://doi.org/10.1117/12.479921

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