Facts about piezo actuator materials

During the last decade, several different PZT materials have been developed world wide. They have been optimised with different dopants to match application specific functions and performance, as high stroke, low hysteresis, low creep, high sensitivity, elevated operating temperature etc.

Noliac is one of the only companies in the world capable of manufacturing multilayer piezoelectric components based upon a choice of different materials, each having optimised properties for specific types of applications. Amongst others, Noliac has prioritised the PZT materials in our portfolio towards optimal actuator properties.

Today these materials can be categorized into three different groups:
 

Hard doped materials are described as medium strain all round PZT material for high dynamic operations and particularly suitable for motors, transformers and applications requiring low heat generation. This material also features the possibility of bipolar operation and can safely be operated up to 200ºC.

Soft doped materials are high strain all round PZT materials for static or medium dynamic applications with high dielectric constant d33.

Electrostrictive PMN material featuring very low hysteresis and creep. PMN has 80% higher Young modulus than PZT materials. Consideration must be given to the high temperature dependence of several properties and the high dielectric constant of this material.
 
It is always a trade off between optimal material properties, when the designer selects a specific material for a given application. In the table below the most important application properties are compared for hard doped, soft doped and electrostrictive materials.

Application property	Hard doped	Soft doped	Electrostrictive
Low loss	++	-	-
High frequency	+	-	-
High stroke	-	++	+
Low capacitance	++	+	-
Low Creep	-	-	++
Low hysteresis	-	-	++
Low temperature coefficients	-	+	-

Generally, hard doped materials have their strength in application where the multilayered piezo component is driven at high frequency, because of low loss and as such low internal heat generation. Soft doped materials have their strength in applications requiring high