Rare earth doping driven multifunctional properties of PbTiO 3 derivatives

Abstract

In the present study rare earth (La, Nd, Sm, Gd) and chromium doped lead titanate ceramics with compositions Pb 0.8 Ln 0.2 Cr 0 & sdot;2 Ti 0 & sdot;8 O 3 were fabricated by using mixed oxide method. The phase formation of the compounds was confirmed through X-ray diffraction study. The compounds exhibit similar crystal structure as that of the pure lead titanate (i.e., tetragonal). However, the tetragonality was found to be increasing with decrease in ionic radii of rare earth dopants. The microstructure of the compounds studied through Field emission scanning electron microscopy (FESEM) was found to be dense with minimal porosity. The average grain size of the compounds goes on increasing with variation in rare earth dopants from La to Gd. The temperature dependent dielectric constant plots exhibit dielectric anomalies at certain temperatures. The compounds exhibit high values of dielectric constant with low dielectric loss. The ac conductivity of the samples is found to be dependent on both temperature and frequency. The compounds exhibit semiconducting NTCR (negative temperature coefficient resistance) type behaviour. The conduction in these materials is carried out mainly by small polarons and oxygen vacancies. The multifunctional behaviour of the materials was confirmed through ferroelectric, magnetic and magnetoelectric coupling studies. Well saturated hysteresis loops were obtained for all the samples at room temperature. The samples exhibit paramagnetic behaviour at room temperature. The coupling between ferroelectric and magnetic order parameters was confirmed through magnetoelectric (ME) coupling study. Among all samples, PLCTO exhibits maximum ME response.