Effect of Q in Piezoelectric Transducers Based on Pb0.88 (Ln)0.08 Ti0.98 Mn0.02 O3 (Ln = La, Eu, Nd, Sm, Gd) Ceramics Used in Human Tissue

Abstract

The dependence of the mechanical quality factor Q is used in the design of piezoelectric transducers based on PbTiO 3 modified by the partial substitution of rare earths for Pb. The Pb 0.88 (Ln) 0.08 Ti 0.98 Mn 0.02 O 3 system (Ln = La, Eu, Nd, Sm, Gd) ceramics are studied in the design of medical ultrasound transducers used in human tissue. The Q value indicates the lack of balance between the piezoelectric ceramic acoustic impedence and the acoustic impedance of the mean wich is in contact with the ceramic. This impedance relationship is important when are designed medical ultrasound transducers used in pulse-echo or continuous Doppler effect systems. The equation of Filipczynsky et al . is used to obtain the Q of ultrasonic transducers coupled acoustically and the electromechanical coupling factor k t (thickness dilatational vibration). Particular case, is when the Eu substitutes for Pb, the ceramic presents ultrahigh electromechanical anisotropy k t /k p M X . Coupling factor for planar extensional vibration k p M 0.