Synthesis and reliability characterization of environment friendly lead-free piezoelectrics

Piezoelectric effect was discovered in certain crystals in late 19th century. However, common use of this effect in industrial applications started with the discovery of Pb(Zr, Ti)O3 or PZT ceramic in the second half of the 20th century. Especially in the last quarter of the 20th century PZT ceramics were used in many advanced technological applications for their high properties and performance. However with increasing environmental concerns and consciousness on human health new limitations and regulations on the use of lead were started to be introduced in many countries. Lead is a toxic element causing many environmental and health problems.For this reason new systems needed to be developed both possessing compatible properties to PZT and being lead-free. Intensive studies have been focused on developing new piezo/ferro electrics either with reduced lead content or completely lead free. A major problem is however low properties and performance. In recent studies, this issue is dealt with systems possessing morphotropic phase boundary (MPB) very similar to PZT that was a phase boundary separating rhombohedral and tetragonal phases. Also to improve physical properties such as increasing bulk density, sintering behavior of compositions were improved via alkaline element oxide additions. This study basically review the literature on lead-free piezoelectric compositions of Bi0.5Na0.5TiO3(BNT) and K0.5Na0.5NbO3(KNN) systems and possibilities of increasing their electrical properities with several strategies such as sintering additives and microstructure control. Electrical characterization study results indicate better piezo/ferro electric properties providing new potentials in synthesized systems to be used in applications as an alternative to toxic Pb-containing PZT.