FATIGUE BEHAVIOR OF PIEZOELECTRIC CERAMICS MATERIAL

Abstract

Piezoelectric ceramics materials are extensively used in many electromechanical systems as sensing and actuating devices. The performance of these devices deteriorates due to cyclic loading either mechanical, electrical, electromechanical, thermo-mechanical, and under thermal shocking conditions. Earlier the effect of electrical and mechanical cycling loadings on the functional performance has been investigated. The properties of commercial lead zirconate titanate degrade during such cycling. However degradation phenomenon of piezoelectric material during thermal shocking is still an area which has to be explored. The decay in functional properties of materials is somewhat called degradation and this terminology used to describe the loss in performance with time due to stress and temperature. The common phenomenon of degradation is aging of the material, which affects the performance of the material with time. This change in performance is thought to be due to re-orientation of dipoles in different configurations. Environment is another degradation phenomenon influence the performance of piezo devices. Output performance of piezoelectric materials changes frequently with the change in temperature, pressure, humidity and moisture. Recently many studies show that water has the profound effect on the performance of piezoelectric materials. Reliability of these smart materials is important and hence there is a requirement to have an extensive study on its functional performance and properties. In actuators mostly disc shaped piezoelectric are used due to their improved properties. A part of this particular research work was to investigate the degradation of thin lead zirconate titanate piezoelectric discs through a series of experimentation to observe its function at variable frequencies in simple tap water, de-ionized water and sodium chloride (NaCl) solutions. Output viperformance has been monitored in real time as peak-peak voltage change. PZT disc found sensitive in performance in various solutions at different frequencies. The results obtained can be utilized as qualitative data for designing of micro electro- mechanical systems. The change in capacitance has been measured by using relevant instrumentation during thermal shocking in de- ionized water. The change in capacitance is a measure of dielectric constant and other piezoelectric properties. Dielectric constant, impedance, tangent loss and dissipation factors are the required parameters and can be measured by using suitable size and shape of piezoelectric materials. In general, piezoelectric ceramics posses the largest electromechanical coupling factor, dielectric constant and lowest dielectric loss. The sudden change in temperature may experience a thermal stress which further changes its above stated properties. Most of the properties are attributed to change in capacitance values at resonance and anti resonance frequencies. In a part of this research work, focus was to determine the various piezoelectric properties by thermal shocking in de-ionized water at resonance frequencies. In another phase piezoelectric ceramics disc has been investigated for its sensitivity at different temperatures and at different frequencies and resistances. A model has been developed to indicate the effect of resistance band at different temperatures. The model of performance characteristics of thin PZT disc under different temperature conditions is a unique finding and may used in selection of particular frequency and resistance range for many piezo devices for the stated conditions. The objective of this research work was to explore the degradation of thin PZT piezoelectric ceramics disc in its performance and change of various piezoelectric viiproperties during thermal cycling and shocking. The present work uncovers the various unattended thermal cycling and shocking condition of stated piezoelectric material. Comprehensive data obtained by real time experimentation may useful for designing of various micro-electromechanical systems.