SELECTION AND REALIZATION OF PIEZOELECTRIC MATERIAL FOR AEROSPACE

APPLICATIONS

By

KRITTIKA KATTI

ANJALI COMAR

P.S.SUKRUTHA

CONTENTS

• Aim• Introduction a) Ring laser gyro (RLG) b) Path length control (PLC) c) Problem faced during PLC

• Experiment work a) Selection of lead-free piezoelectric material b) Preparation process of BaTiO3 • Results a) X-ray diffraction b) Microstructure c) SEM

• Conclusion• Future scope of work

AIM

• The main objective of this study is to replace “lead zirconate titanate” (PZT) with a “lead-free” piezo ceramic which does not undergo property degradation in any environment, including x-rays.

INTRODUCTION

• Ring laser gyro: A ring laser gyroscope (RLG) consists of a ring laser having two counter-propagating modes over the same path in order to detect rotation. It operates on the principle of the Sagnac effect.

• Path length control: The path length control mechanism is required to compensate for dimensional changes in the ring laser gyro block due to temperature variations or instabilities in the materials. Path length is commonly controlled utilizing piezoelectric devices which adjust the location of a movable mirror in the ring laser gyro cavity.

RING LASER GYRO

SET UP

PROBLEMS FACED DURING PATH LENGTH CONTROL

Three primary areas of concern are :1) The path length changes caused by x-ray heating of the

PLC transducer assembly2) The recovery time of the PLC subsystem from high intensity

x-radiation 3) The potential for unidentifiable mode changes caused by x-

ray heating.

Some “mode hopping” transient motions were produced by the PLC transducer when subject to x-ray exposure

LASER GYRO INPUT VS PATH LENGTH

WORK CARRIED OUT

• Selection of lead-free piezoelectric materials

A low atomic number (Z) material has been selected because for a given x-ray dosage, different atoms extract energy about as Z^4.

According to the average atomic mass and compared to the

PbZrO3 - PbTiO3 presently used in the PLC transducer 35 materials have been identified.

Out of 35 materials, 16 materials have been selected which have a perovskite structure.

Some of the materials identified under perovskite group were barium titanate, lithium tantalate, lithium niobate, potassium tantalate, lithium

iodate,potassium lithium niobate, potassium lithium tantalate etc.

From the extensive list of lead-free materials available, we have selected barium titanate for our study because of its high piezoelectric properties.

BaTiO3 is a ferroelectric ceramic material having the appearance of a whitepowder or transparent crystals.

STRUCTURE OF

BARIUM TITANATE

BaCO3 (S) + TiO2(S) BaTiO3 (S)+ CO2 (g)

BaCO3 + TiO2

Weighing

Grinding

Precalcination at 1000°C for 2hr

Reground to Powders

Uni-axial Pressing

(Pelletizing)

Final Sintering

1000°C for 0.5 hr

Final stage sintering at 1350

for 3hr

Two StepsDense BaTiO3

Flowchart for Preparation Processing of Dense BaTiO3 by

Solid State Reaction

Reaction Kinetics and equation

Characterizations

Precursors are taken in Mole % compositions

• Weighing of the constituent powders

Molecular weight of barium carbonate (BaCO3) = 197g Molecular weight of titanium dioxide (TiO2) = 79.87g

1mole of BaTiO3 = 0.5 moles of BaCO3 + 0.5 moles of TiO2 10 moles of BaTiO3 = 5 moles of BaCO3 + 5 moles of TiO2

Weight of TiO2 → (5*79.87) / 138.435 = 2.884 g Weight of BaCO3 → (5*197) / 138.435 = 7.115g Weight of BaTiO3→ 9.999g

• Sintering cycle

RESULTS

Powder X-Ray Diffraction Pattern of Barium Titanate

Crystal structure: Tetragonal

• X-RAY DIFFRACTION PATTERN

MICROSTRUCTURE

MAGNIFICATION- 200X

STANDARD ELECTRON MICROSCOPIC IMAGES (SEM)

Tetragonal Shaped BaTiO3

Grains

CONCLUSION

• The materials used in the PLC transducer were analyzed and the high atomic number lead zirconate-lead titanate (PZT) materials used in the transducer was considered as a cause for the mode hopping transient motions.

• Therefore, low average atomic mass piezoelectric ceramic materials were identified in this project which appear to have sufficient field-versus-displacement to be used in replacement of the present lead zirconate- lead titanate.

• Among the materials identified, barium titanate has been selected because of its good piezoelectric properties and ready availability.

FUTURE SCOPE OF WORK

• Poling of the already prepared barium titanate sample will be carried out.

• In order to build a stack actuator, additional barium titanate samples will be prepared.

• Realization of barium titanate stack actuator for RLG application.

• Realization of other lead-free materials (currently sodium potassium niobate) will be carried out.