Mod_1_smart_mat_lec_2.pdf
- 1. Module 1: Overview of Smart Materials Module 1: Overview of Smart Materials Bishakh Bhattacharya & Nachiketa Tiwari Department of Mechanical Engineering Department of Mechanical Engineering Indian Institute of Technology, Kanpur
- 2. Lecture #2: Introduction to Piezoelectric Materials History of Piezoelectricty Piezoelectric Materials Piezoelectric Materials How to prepare a Pi i A t t ? Piezoceramic Actuator? Constitutive Relationship Co st tut e e at o s p Piezoceramic Polymers & Composites Composites Bimorphs & Piezostacks p
- 3. History of Piezoelectricity History of Piezoelectricity • Piezoelectricity i e Electricity from • Piezoelectricity i.e. Electricity from Pressure was discovered by Pierre and C Jacque Curie in 1880 • Contemporary: Contact Electricity – Static Contemporary: Contact Electricity Static Electricity generated from Friction P l t i it El t i it t d f • Pyroelectricity: Electricity generated from crystals while heating
- 4. Who’s who in Piezoelectricity? Who s who in Piezoelectricity? Pierre Curie (1859-1906), Nobel Prize in Physics, 1903 Direct Piezoelectric Effect Gabriel Lippmann (1845-1921), Nobel Prize in Physics, 1908 Reverse Piezoelectric Effect
- 5. Piezoelectricity – Time Line Piezoelectricity Time Line • The effect observed by Pierre and Jacque Curie is called as Direct Piezoelectric Effect (Hankel is called as Direct Piezoelectric Effect (Hankel 1881) Th di t ff t f d i Zi Bl d • The direct effect was found in Zinc Blende, Boracite, Tourmaline, Quartz, Cane Sugar and R h ll S lt Rochelle Salt • The reverse effect was theoretically predicted by Lippman (1881) and experimentally confirmed by Voight in 1894 • First application – Langvein (1917) in Sonar Transducer (composite made of steel plate & ( p p quartz) – later Ceramic Phonograph, Ceramic Electret Microphone
- 6. Piezoelectricity in Perovskites (1949-60) Perovskite: A Ternary (3 Component structure) Perovskite: A Ternary (3 Component structure) Example: BaTiO3 a common piezoelectric material Tetragonal Symmetry with Dipole moment below C i T Curie Temperature Similar material: PZT family LiNb family PbNb family YMn family Similar material: PZT family, LiNb family, PbNb family, YMn family, (NH4)Cd family (1970--)
- 8. How to prepare a Piezoceramic Actuator? St t ith fi d f t t l • Start with fine powders of component metal oxides (PZT or Barium Titanate family) e.g.. for PZT you need PbO ZrO and TiO powders PZT you need PbO, ZrO2 and TiO2 powders • Mix them in fixed proportions U i bi d • Use an organic binder • Form into specific shapes • Heat for a specific time and specified temperature 650-800oC • Cool – apply electrode (sputtering) • Polarize the sensor/actuator using a DC electric field
- 9. 4 steps for Powder Processing p g
- 10. Constitutive Equation of Piezoelectricity X E dX D E X Direct Effect Converse X-stress x-strain D-electric displacement/flux dE X S x E Converse Effect X stress, x strain, D electric displacement/flux density, S-compliance, E-Electric field intensity permittivity d piezoelectric constant -permittivity, d-piezoelectric constant Superscripts denote the measurement of itti it t t t t d li t permittivity at constant stress and compliance at constant electric field intensity
- 11. Response of a Piezo-fibre p
- 12. Electromechanical Coupling Coefficient Electromechanical Coupling Coefficient • Due to nonlinearity the equations represented in Variational form: p E d X S E X d D E x E d X S x E • Electromechanical coupling Coefficient: 2 2 2 1 12 2 2 / W W W k W12 – Piezoelectric Energy Density W1 W12 Piezoelectric Energy Density, W1 Mechanical and W2 Electrical energy density
- 13. Commercial Piezoelectric Material Property Set Commercial Piezoelectric Material Property Set Prp unit BaTiO3 PZT-A PZT-B Pb Nb2O6 LiNbO3 Pb Ti O3 Mg/m3 5 7 7 9 7 7 5 9 4 6 7 1 Mg/m 5.7 7.9 7.7 5.9 4.6 7.1 k31 .21 .33 .39 .04 .02 .05 k31 k33 .49 .68 .72 .38 .17 .35 d31 pCN-1 79 119 234 11 .85 7.4 S m2/N 8.6 12.2 14.5 29 5.8 11
- 14. A few observations A few observations • PZT family has highest piezoelectric coupling p g • Curie Point PZT family 220-315oC, same for Li family 600 1200oC for Li family 600-1200oC • Instead of polycrystalline Piezoceramics a single cut PMN could give k33 = 0.92 and d33 = 2070 pC/N give k33 0.92 and d33 2070 pC/N
- 15. Piezoelectric Polymer y • PVF2 (Poly Vinylidene Fluoride) a semi- crystalline polymer consist of long-chain y p y g molecules with the repeat unit of CF2CH2 • Form I PVDF (all trans) shows all chain • Form I PVDF (all trans) shows all chain oriented parallel to the axis of the unit cell and the dipoles pointing in the same direction • d31 4.2-19 pC/N (for PZT ~ 234) d31 4.2 19 pC/N (for PZT 234) • k31 3-14.7% • E – 1.6 – 3.8 GPa
- 16. Piezoelectric Composite Piezoelectric Composite • Composite made of a polymer and PZT • Polymer phase – lower density, permittivity and y p y p y increase elastic compliance • Smaller PZT particles (5-10 m) in Polyurethane Smaller PZT particles (5 10 m) in Polyurethane (PU) matrix • Larger 120m particles in a silicone rubber • Larger 120m particles in a silicone rubber matrix Skinner et al: Smaller particles generate series • Skinner et al: Smaller particles generate series connectivity, while larger parallel
- 17. Piezoelectric Composites Piezoelectric Composites • For series connection, even very low volume f ti f l (1%) d ti ll d ‘d’ fraction of polymer (1%) drastically reduces ‘d’ however ‘g’ remains unaffected • For parallel connection ‘d’ remains unchanged, ‘g’ increases • Replamineform process to enhance interconnectivity I i ti f C l Inspiration from Coral structure: Narrow pore-size p distribution, complete pore interconnectivity
- 18. Applications: Bimorph Applications: Bimorph D31 Actuator D31 Sensor
- 21. END OF LECTURE 2