FABRICATION AND TESTING OF PIEZOELECTRIC BISMUTH TITANATE FOR USE AS A HIGH TEMEPRATURE ULTRASONIC
Open Access
- Author:
- Searfass, Clifford
- Graduate Program:
- Engineering Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 20, 2008
- Committee Members:
- Bernhard R Tittmann, Thesis Advisor/Co-Advisor
Bernhard R Tittmann, Dissertation Advisor/Co-Advisor - Keywords:
- Ultrasound
Bismuth titanate
sol-gel
microwave sintering
high temperature - Abstract:
- Bismuth titanate (Bi4Ti3O12) is a material with potential use as an ultrasonic transducer in high temperature (>400 oC) environments and as a replacement of lead containing materials such as lead zirconate titanate compounds. The objective of this study is to validate bismuth titanate for use as an ultrasonic transducer in ambient conditions and at elevated temperatures. This includes testing the capabilities of generating longitudinal, Lamb, and Rayleigh waves. A spray on sol-gel deposition technique of bismuth titanate is adapted and used for material fabrication because it eliminates needs for ultrasonic couplants at high temperatures and shows promise for use in the evaluation of structures with complicated geometries. Substrate adhesion and transduction efficiency are improved by incorporating microwave sintering and high intensity ultrasonic mixing into the fabrication process. Tested sample substrates include stainless steel and titanium. Tested samples show large preference to generate vibration modes in the direction of strongest polarization. This makes bismuth titanate an excellent candidate as a longitudinal wave transducer. Longitudinal wave transducers with signal-to-noise ratios as high as 64 dB have been fabricated. Results presented in this thesis show that longitudinal wave transducers can achieve operation up to 680 oC and Lamb wave transducers can achieve operation up to 617 oC.