Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

New PNNZT composition (high permittivity and low loss)

A new piezoelectric composition has been developed with an unusual combination of high permittivity and coupling on one hand and low dielectric and mechanical losses on the other hand. The composition system chosen for this work is the relaxor-based Pb[(Ni_1/3 Nb_2/3 )_x Zr_y Ti_1-x-y ]O_3 system, commonly abbreviated PNNZT. Very high permittivities can be obtained in this system without sacrificing too much in terms of Curie point, and the novelty is that the dielectric and mechanical losses have been reduced by doping.

Selected properties for the new compositions are: high free and clamped permittivities (2800 and 1400, respectively), dielectric loss tan delta of only 0.003, mechanical quality factor Q_m above 1500, Curie point T_C of 225ºC, high planar and thickness coupling factors (k_p = 0.59, k_t = 0.48) and high piezoelectric coefficients (e.g., d_33 ~ 500pC/N). The new composition is already being commercialised with the type number Pz54.

The new material will find use in applications where a combination of the traditional soft and hard PZT properties is requested, namely high permittivity for electrical impedance matching and high sensitivity for good efficiency or signal/noise ratio as well as low dielectric and mechanical losses for high-power operation. An important example is the growing field of high-intensity focussed ultrasound (HIFU), and also underwater acoustics and medical diagnostics are very interesting application fields.

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Hejreskovvej, 18A
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