Piezoelectric_Materials_Flashcards
(29 cards)
What are the two key properties of piezoelectric materials?
When deformed, they generate a measurable electrical charge. When subjected to an electric field, they elongate.
What applications are based on the properties of piezoelectric materials?
Sensor and actuator applications.
What is spontaneous polarization (Ps) linked to?
The pyroelectric effect.
How does spontaneous polarization behave under thermal changes?
It depends on temperature and affects ferroelectric materials’ stability.
What is the Curie point?
The temperature above which materials lose their permanent magnetic properties.
What is the formula for the direct piezoelectric effect?
P = dT, where d is the piezoelectric charge constant and T is applied mechanical stress.
How do piezoelectric materials convert mechanical energy?
They convert mechanical energy into electrical energy.
What is the formula for electric displacement in the direct piezoelectric effect?
D = dT + eT E, where eT is the dielectric constant at constant stress.
What happens in the inverse piezoelectric effect?
When an electric field is applied, the material deforms.
What is the key equation for the inverse piezoelectric effect?
S = dE or S = gD, where S is strain, d is the charge constant, and E is the electric field.
What is Hooke’s Law in the context of piezoelectric materials?
S = sT, where s is the reciprocal of Young’s modulus and T is tensile stress.
What does the piezoelectric charge constant (d) measure?
The ratio of generated electric charge to applied stress.
What does the piezoelectric voltage constant (g) relate?
The generated electric field to applied stress.
What does anisotropy in piezoelectric materials mean?
Their properties depend on the direction of the applied field and deformation.
What are examples of piezoelectric constants describing anisotropy?
d33, d31, and d36.
What is the morphotropic phase boundary (MPB)?
A region in ferroelectric ceramics where optimal piezoelectric properties occur due to coexisting phases.
What properties are enhanced at the morphotropic phase boundary?
Higher polarization and strain values.
What are the characteristics of piezoelectric ceramics?
High piezoelectric coefficients and coupling factors, but brittle and often contain toxic lead.
What are the characteristics of piezoelectric polymers?
Lightweight, flexible, with lower piezoelectric constants, suitable for acoustic and mechanical applications.
What is an example of a piezoelectric polymer?
PVDF (Polyvinylidene fluoride).
What are the advantages of lead-free ferroelectric materials?
Eco-friendly alternatives to traditional lead-based piezoelectric materials.
What are the challenges of lead-free ferroelectric materials?
Low Curie temperature, complex manufacturing, and lower piezoelectric coefficients.
What are examples of lead-free ferroelectric materials?
Barium titanate (BaTiO3), lithium niobate (LiNbO3), potassium-sodium niobate (KNN).
What are the types of piezoelectric composites?
Stack actuator (2-2), microfiber composites (1-3), and active fiber composites (AFC).
