Small changes boosts efficacy of piezoceramics: IISc study

Piezoelectric materials are suitable for wide-ranging applications, from ultrasound imaging in hospitals to actuators in guided missiles

Researchers at the Indian Institute of Science (IISc) and their collaborators in a new study have revealed that the efficacy of a commonly-used piezoelectric ceramic material can be dramatically increased just by reducing its thickness.

Piezoelectric materials are suitable for wide-ranging applications, from ultrasound imaging in hospitals to actuators in guided missiles.

“Piezoelectric materials deform (stretch or contract) when an electric field is applied. Single crystals of some synthetic piezoelectrics show large longitudinal electrostrain (>1%), a value that indicates how much the material deforms in the direction of the field. But such materials are rare, and mass-producing single crystals is costly. They are therefore used only for niche applications,” IISc said.

For most commercial applications, the more economical polycrystalline piezoelectric ceramics are used. However, these show much lower longitudinal strain (0.2-0.4%).

“The maximum electrostrain reported in polycrystalline lead-free piezoelectrics is 0.7%. Our intention was to increase the strain beyond this,” said Gobinda Das Adhikary, first author and former PhD student at the Department of Materials Engineering (MatE), IISc.

IISc added that every grain in a piezoceramic contains spontaneously polarised regions called domains that switch their orientation towards the electric field in tandem, causing the material to deform as a whole.

Grains near the surface of the material are better at deforming because they are freer, whereas deep inside, they are more tightly bound by other grains from all sides and find it difficult to deform. In commonly-used piezoceramic discs (typically 10 mm in diameter and 1 mm thick) most grains deform very less, resulting in an overall low longitudinal strain, said Rajeev Ranjan, Professor at MatE and corresponding author.

While tweaking the size and shape of a widely-known piezoceramic called PZT (lead zirconate titanate), Ranjan’s team discovered that when the thickness of a circular PZT disc was reduced from 0.7 mm to 0.2 mm, its electrostrain jumped from 0.3% to 1%.

Published - January 10, 2025 12:22 am IST