Novel piezoelectric ceramic-polymer aligned composites via the freeze casting method for high frequency transducer applications

Abstract

Novel piezoelectric ceramic-polymer aligned (2-2) composites were prepared via the freeze casting method. The dielectric constant of the composites versus temperature was determined. The polarization versus field plots for the PZT-5A and the PMN-10PT aligned composite samples show an good ferroelectric behavior for both samples. K t of PZT-5A composite was measured to be 0.54, which is similar to that of single phase ceramic. The piezoelectric coefficient (d 33 ) of PZT-5H composite was determined to be ~250 pC/N. The measured pulse echo waveform and the normalized frequency spectrum of the PZT-5A aligned composite single element ultrasound transducer showed that the center frequency of the transducer was 58 MHz and the bandwidth at -6dB was around 70%.

Freeze casting – A review of processing, microstructure and properties via the open data repository, FreezeCasting.net

“…The most commonly utilized dispersants for aqueous Al2O3 suspensions contain a carboxylic acid functional group (e.g. Darvan dispersants) [369][370][371]. In this case, as the pH of the suspension is increased, greater dissociation of the functional group is realized; repulsion between particles is achieved because particle surfaces are negatively charged due to the adsorption of dispersant molecules and ζ of the suspension decreases.…”

High piezoelectric sensitivity and hydrostatic figures of merit in unidirectional porous ferroelectric ceramics fabricated by freeze casting

“…In this paper, we exploit the inspiration drawn from the high strength of natural nacre with a layered microstructure [17], and the ability of freeze casting, also called ice-templating [18][19][20] as an effective way to mimic the structure of nacre by building an oriented ceramic structure within a unidirectional temperature gradient, with the realisation of anisotropic properties in directions parallel and perpendicular to the temperature gradient/pore channel. To date, there have been a number of studies on freeze-cast piezoelectric ceramics that have utilised camphene-based [21][22][23], tert-butyl alcohol (TBA)-based [24][25][26][27][28][29][30][31][32][33][34] suspensions to achieve 3-1, 3-2 and 3-3 connectivity piezoceramic-based composites, and water-based [34][35][36][37][38][39][40] suspensions for 2-2 connectivity composites. The majority of the investigations above were focused on the properties of the freeze-cast parallel to the temperature gradient/pore channel, and there is little work on comparing the piezoelectric properties of freeze-cast ceramics both parallel and perpendicular to the temperature gradient/pore channel.…”