Structural and electrical properties of lanthanum-substituted lead titanate ceramics

Abstract

The effect of lanthanum substitution on the structural, dielectric and piezoelectric properties of lead calcium titanate (PCT) ceramics is studied. Samples with compositional formula Pb<inf>0.76-x</inf>La<inf>x</inf>Ca <inf>0.24</inf>Ti<inf>0.98</inf>Mn<inf>0.02</inf>O<inf>3</inf> (PLCT) (x = 0-0.08, in steps of 0.02) were prepared by the conventional dry ceramic technique. Phase and structural analysis was carried out using XRD and SEM respectively. X-ray analysis confirmed the formation of single-phase compound with tetragonal crystal structure. Dielectric properties were studied in detail as a function of frequency and temperature. The Curie temperature (T <inf>C</inf>) and tetragonality (c/a) was found to decrease with increase in lanthanum content. The Curie temperature was also confirmed from the thermal-expansion behaviour of the sintered samples. Piezoelectric coefficients (d<inf>33</inf>, d<inf>31</inf>, g<inf>33</inf>, g<inf>31</inf>, g<inf>h</inf>, d<inf>h</inf>, k<inf>t</inf> and k<inf>p</inf>) were measured at room temperature. From this study it is found that La3+ substitution helps in the improvement of electro-mechanical anisotropy. © 2005 Taylor & Francis. © 2008 Elsevier B.V., All rights reserved.