A review on lithium doped lead-free piezoelectric materials

In the past, innovation of lead-free piezoelectric materials in ultrasonic transducers, actuators, and sensors have been the driving force for new developments in piezoelectric ceramics. The factors such as type of materials, dopant, synthesis process is influencing the lead-free piezoelectric properties. Among the factors, Lithium dopants on lead-free of piezoelectric materials were less discovered in the available literature. This paper is intended to give a brief review on the most Lithium, Li doped lead-free piezoelectric material from 2012 to 2021 to correlate the amount of doping and sample preparation method with performance of the piezoelectric materials. The details of each article have been reviewed, including the sample preparation, structure and microstructure, density, ρ, electrical properties such as dielectric constant, ɛr, piezoelectric coefficient, d33, ferroelectric and mechanical properties. The findings of the literature review showed that the highest d33 obtained so far was 530 pC/N when 0.5 wt% Li2CO3 was doped in (Ba0.85Ca0.15) (Ti0.9Zr0.1)O3 (BCTZ). Though there has been a tremendous increase in the amount of literature about piezoelectric materials in the last two decades, this paper presents an update to our previous review paper by summarising the notable developments of Li-doped lead-free piezoelectric materials from 2012 to 2021.