Invariants of electromechanical coupling coefficients in piezoceramics

Abstract

The relationships between coefficients of electromechanical coupling (CEMC) of various types of piezoceramic resonator (PR) vibrations are considered. Being constant for a given piezoceramic state, the range of variation of piezoceramics dielectric permittivity from a mechanically "free" condition at relatively low frequencies up to an "overall clamped" condition at high frequencies is determined by a consecutive "clamping", caused by a complex of CEMCs of various particular vibrational modes peculiar to the resonator. As the difference between "free" and "overall clamped" permittivities is always determined by the maximal piezomaterial k i3 coupling coefficient, the difference does not depend on the path that was gone through the low-high frequency range, which includes all the vibrational modes possible for a particular PR. The influence of the piezoelectric and elastic anisotropy of lead-zirconatetitanate (PZT) piezoceramic materials on relative CEMC variations was experimentally investigated.

Large Effective-Strain Piezoelectric Actuators Using Nested Cellular Architecture With Exponential Strain Amplification Mechanisms

“…where N film is the number of PZT films along the actuation direction, d 33 is piezoelectric coefficient, and V (>0) is voltage applied to each PZT film. Strictly speaking, the piezoelectric coefficient d 33 is not a constant; according to [24] it may vary significantly as strain gets larger. In this paper, however, it is assumed to be constant.…”

Piezoelectric transformer parameters evaluation

“…[6], creating a convenient electrical equivalent circuit that will represent the PT behavior, is not a simple matter. Such a circuit could estimate the equivalent PT parameters only under the very narrow range of frequencies and electrical loads.…”

Quality factor concept in piezoceramic transformer performance description

“…where s is the total dynamic PT compliance, s 1 is the compliance of the input PT section, s 2 is the dynamic compliance of the output PT section, which changes from min s 2 = s E 33 1 − k 2 33 = s D 33 for the open-circuited (o.c.) output PT section up to max s 2 = s E 33 for the short-circuit (s.c.) condition, and:…”

“…According to (12), (13), a method based on amplitude measurements [10] of the PT resonance admittance Y in (r) , or PT conductance Re Y in(r) , takes into account the dielectric losses; a method based on susceptance Im Y in (f ) extreme frequencies measurement [32] are not under influence of the dielectric losses. For an elementary unloaded piezoceramic resonator, the dielectric loss factor typically δ 33 k 2 (j) Q m , and the quality factors difference is extremely low. However, for a loaded and/or strong field excited PT, the dielectric loss factor greatly increases and the system's vibrational quality factor reaches as low as ∼10 units; in such a situation the quality factors difference is significant.…”