Fabrication, modelling and use of porous ceramics for ultrasonic transducer applications

Journal of Electroceramics (Impact Factor: 1.74). 08/2007; 19(1):127-139. DOI: 10.1007/s10832-007-9117-3


Porous ceramics are of interest for ultrasonic transducer applications. Porosity allows to decrease acoustical impedance,
thus improving transfer of acoustical energy to water or biological tissues. For underwater applications, the dhgh figure of merit can also be improved as compared to dense materials. In the case of high frequency transducers, namely for
high resolution medical imaging, thick film technology can be used. The active films are generally porous and this porosity
must be controlled. An unpoled porous PZT substrate is also shown to be an interesting solution since it can be used in a
screen-printing process and as a backing for the transducer. This paper describes the fabrication process to obtain such materials,
presents microstructure analysis as well as functional properties of materials. Modelling is also performed and results are
compared to measurements. Finally, transducer issues are addressed through modelling and design of several configurations.
The key parameters are identified and their effect on transducer performance is discussed. A comparison with dense materials
is performed and results are discussed to highlight in which cases porous piezoceramics can improve transducer performance,
and improvements are quantified.

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    • "or 10–12 Â 10 6 V/m [25]) and results in a more uniform temperature throughout the sample. However, in the present work, samples that were poled in oil exhibited substantial hydrophobicity due to oil penetrating the pore surfaces. "
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    ABSTRACT: Membranes utilized for water and wastewater treatment are susceptible to fouling. Fouling leads to gradual flux decline, possible loss of selectivity and increased operational costs. Conventional de-fouling strategies such as backwashing and chemical cleaning can be effective, but have inherent disadvantages. Recently, application of ultrasound was shown to be an effective cleaning method but, thus far, has been applied only with the ultrasonic source in close proximity to the membrane. In this work we demonstrate for the first time, a new membrane design in which ultrasound for de-fouling is generated from within the membrane structure. To test the feasibility of this idea, we fabricated porous, poled and unpoled piezoelectric ceramic microfiltration membranes and performed filtration tests with a fouling dispersion containing 10 mg/L of 500 nm latex particles. To generate ultrasound from within the membrane, an alternating voltage was applied across the membrane with the feed side electrode located 1 mm from the membrane surface. In the absence of voltage, the flux decreased by 420% within 3 h of filtration. Conversely, when an alternating voltage was applied in intermittent pulses, no water flux decrease was observed over 3 h of filtration, demonstrating the feasibility of membranes with built-in de-fouling functionality.
    Journal of Membrane Science 08/2015; 494:130-135. DOI:10.1016/j.memsci.2015.07.058 · 5.06 Impact Factor
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    • "The backing was made of porous unpoled lead zirconate titanate (PZT) based on Ferroperm Pz37 composition (meggitt a/s) [19]. This porous material offers several advantages for transducer properties (in particular for the center element) [20]. "
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    ABSTRACT: Detection of high-order nonlinear components issued from microbubbles has emerged as a sensitive method for contrast agent imaging. Nevertheless, the detection of these high-frequency components, including the third, fourth, and fifth harmonics, remains challenging because of the lack of transducer sensitivity and bandwidth. In this context, we propose a new design of imaging transducer based on a simple fabrication process for high-frequency nonlinear imaging. The transducer is composed of two elements: the outer low-frequency (LF) element was centered at 4 MHz and used in transmit mode, whereas the inner high-frequency (HF) element centered at 14 MHz was used in receive mode. The center element was pad-printed using a lead zirconate titanate (PZT) paste. The outer element was molded using a commercial PZT, and curved porous unpoled PZT was used as backing. Each piezoelectric element was characterized to determine the electromechanical performance with thickness coupling factor around 45%. After the assembly of the two transducer elements, hydrophone measurements (electroacoustic responses and radiation patterns) were carried out and demonstrated a large bandwidth (70% at -3 dB) of the HF transducer. Finally, the transducer was evaluated for contrast agent imaging using contrast agent microbubbles. The results showed that harmonic components (up to the sixth harmonic) of the microbubbles were successfully detected. Moreover, images from a flow phantom were acquired and demonstrated the potential of the transducer for high-frequency nonlinear contrast imaging.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control 12/2013; 60(12):2634-44. DOI:10.1109/TUFFC.2013.2862 · 1.51 Impact Factor
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    • "Porous PZT ceramics have been of great interest and technological importance in ultrasonic applications such as hydrophones, actuators and underwater transducers [1] [2] [3]. This results from their ability to accomplish coupling between mechanical and electric signals as well as their possibility of obtaining very high values for some piezoelectric coefficients compared with dense materials. "
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    ABSTRACT: Porous lead zirconate titanate (PZT) ceramics with interconnected pores were fabricated by using a novel tert-butyl alcohol (TBA)-based gel-casting method. The resultant samples were sintered at different temperatures and subsequently characterized in terms of both microstructure and piezoelectric properties to study effects of sintering behavior. Both microstructure and piezoelectric properties exhibited obvious dependence on sintering temperature. It was noted that porosity and grain size played dominant roles in determining the magnitudes of dielectric constant (ɛ) and piezoelectric constant d33, respectively. With the increase of sintering temperature, the porosity declined and the grain size increased which exerted opposite influences on piezoelectric properties mainly via ɛ and d33. Since anti-interference ability of the ceramic correlates linearly with ɛ, it is possible to adjust sintering temperature to tailor porosity and pore morphology in order to achieve optimum piezoelectric properties as well as relatively high anti-interference ability.
    Ceramics International 03/2010; 36(2):549-554. DOI:10.1016/j.ceramint.2009.09.022 · 2.61 Impact Factor
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