Piezo is a Greek word derived from “piezein”, which means press or squeeze. Therefore, piezoelectricity means squeezing electricity. Piezoelectricity is the ability of certain crystalline materials to develop an electric charge proportional to a mechanical stress. Materials showing this phenomenon also show the reverse, deformation proportional to an applied voltage.
For piezoelectric interaction to exist it is necessary that certain axes of the medium intrinsically posses a one-wayness or polarity. The polarity needed to impart piezoelectric properties can be given to an originally isotropic polycrystalline ceramic by application of a strong electric field, known as poling.
The creation of useful piezoelectric ceramics by treatment of a polycrystalline material depends on ferroelectricity. Ferroelectricity is the presence of a spontaneous electric moment in crystal which can be changed in orientation between two or more distinct crystallographic directions by applying an external electric field.
There are three basic steps in understanding of piezoelectricity in ceramics. First is the high dielectric constant. Second step is the realization that the cause of this high dielectric constant is ferroelectricity. Third step is the poling of these ceramics.
PZT (Lead-Zirconate-Titanate) based piezo ceramics is currently the most widely used piezoelectric material in the world. PZT material is classified into two types, hard & soft grades.
Hard Grade Piezoelectric ceramics are more suitable for dynamic applications like high voltage and high-power generators and transducers. Being hard it can withstand high levels of electrical excitations and mechanical stresses.Sparkler’s Hard Grades – SP 4 & SP 8
Soft Grade Piezoelectric ceramics provide higher sensitivity, permittivity and are well suited for static applications. They also have higher piezoelectric coefficients compared to hard grades of piezoelectric ceramics. These grades find extensive use in a variety of sensors, pick-ups, low power motor type transducers, receivers and low power generatorsSparkler’s Soft Grades - SP-5A, SP-5J, SP-5H