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Quasi-longitudinal (QL) Anisimkin Jr.' modes discovered recently in quartz plates are found now in 2 other piezoelectric crystals, belonging to trigonal symmetry. In 128degY,X+90deg-LiNbO3, 2 different QL modes may propagate simultaneously for small plate thickness h/lambda = 0 to 0.06 (h is thickness, lambda is wavelength). The velocity of the 1st mode, v1, is close to the longitudinal bulk wave velocity vL. It is varied with h/lambda and piezoelectrically stiffened (maximum Kn 2 = 39% at h/lambda = 0.08). The velocity of the 2nd QL mode, v2, is close to the shear-horizontal bulk wave velocity vQSH, not varied with h/lambda and not stiffened (Kn 2 = 0). On the contrary, 210degY,X-Te crystal supports only one QL-mode, but it is unusually wideranging and low-dispersive: the mode exists for all h/lambda from 0 to 2.5 with velocity vn almost permanent and equal to vL in the whole range. This mode is piezoelectrically stiffened (maximum Kn 2 = 2% at h/lambda = 0.13). The variety of the Anisimkin Jr.' modes in different crystals makes them attractive for liquid sensors, where the amount of suitable waves is very restricted.
Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on (Volume:56 , Issue: 5 )
Date of Publication: May 2009