Derek Sanderson

Tulane University

Chemical Engineering, Mathematics
Advisor: Dr. Keith Bowman

Project Title: Piezoelectric Materials

Introduction

The piezoelectric constant (d33 for our purposes) is the ratio of mechanical strain induced along the poling axis per unit of electric field applied along that same axis. It has been observed in this research group that the measured d33 value by the Pennebaker 8000 tester decreases with time. This decrease in a lithium niobate sample was shown to be about 15-20% in 40 min. but remained relatively constant after that. The reasons and possible mechanisms for this decrease will be investigated and hopefully determined in this project.

Project Objectives

  • Confirm previous results of decreasing constants
  • Determine possibility of equipment error
  • Gather data through various experiments to pinpoint mechanism of decrease

Experimental Approach

All experiments have been carried out on the Pennebaker Model 8000 Piezo d33 Tester from American Piezo Ceramics Inc. Numerous different combinations of variables were carried out such as varying tightness of clamping mechanism, amount of warming up time allowed for the tester, measurement time lengths, machine rest time in between measurements, etc.

Research Findings

Due to a modified timetable, as of this deadline only 3 days of research have been carried out. The data currently suggests that the decreasing readings are material related and not due to operator or equipment error. Further investigation is necessary however to completely rule out these possibilities before extensive research into possible internal mechanisms is carried out.


Fig.1: Plot of decreasing d33 constant vs. time for 3 hours measurements were taken as a range over 30 seconds at specified time.
Fig.2: Plot of the range in d33 values with respect to time, significance of this trend is unknown.

Final Presentation