Electromechanical properties of PbTiO3 based piezoelectric ceramics and energy harvesting application of their flexible polymer composites

Abstract

Ferroelectric and piezoelectric polycrystalline ceramics exhibiting large electromechanical response are sought after in electronic devices such as actuators, transducers in sonar, sensors, accelerators, aerospace, telecommunication, automotive industries, and ultrasonic motors. Ever since the discovery of large electromechanical performance at the morphotropic phase boundary (MPB) composition x=0.52 of Pb (ZrxTi1-x)O3 (PZT), a solid solution of lead zirconate and lead titanate, significant efforts and development has been made in understanding of various aspects contributing to these superlative properties. Morphotropic phase boundary (MPB) compositions separate ferroelectric phases with two different crystallographic symmetries (rhombohedral and tetragonal in PZT) and this inter-ferroelectric structural instability at MPB results in exceptional electromechanical response. This understanding of the significance of composition driven interphase instability led to exploration of new MPB based systems. Lead titanate (PbTiO3), an end member of PZT solid solution is a classical displacive ferroelectric which was discovered way back in 1950. PbTiO3 with tetragonal (P4mm) structure has one of the highest values of tetragonal distortion (c/a ≈ 1.063) among the ferroelectric perovskites and large spontaneous polarization (Ps). This encouraged research community to exploration of various ferroelectric, piezoelectric ceramic with solid solution of lead titanate. PbTiO3 based ferroelectric and piezoelectric ceramics like Pb (ZrxTi1-x) O3 (PZT), (1-x) PbTiO3-(x) BiScO3 (PT-BS), PMN-PT have since dominated the research field owing to their superior electromechanical properties. The focus of the thesis has been on PbTiO3 and its solid solution namely, Pb (ZrxTi1-x) O3 PZT, (1-x) PbTiO3-(x)Bi(Ni1/2Hf1/2)O3 PT-BNH, (1-x)PbTiO3-(x)Bi(Ni1/2Zr1/2)O3 PT-BNZ, (1-x) PbTiO3-(x)BiScO3 (PT-BS) PTBS, (1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 PMN-PT. We have also fine-tuned various parameter to enhance the piezoelectric performance and demonstrate the energy harvesting application of these ferroelectric ceramic as a composite in flexible polymer matrix.