Saravanan Lakshmanan,S.V. Rajasekarana and R. Jayavel

1. Centre for Nanoscience and Technology
Anna University
Chennai
India
 
2. Crystal Growth Centre
Anna University
Chennai
India

ljsaravanan@yahoo.co.in

Lead based piezoelectric single crystals of complex perovskites structure have enormous industrial applications due to their high dielectric and piezoelectric properties. Relaxor is a class of ferroelectric with a general formula of Pb(B1,B2)O3, where B1 is a low valence cation (such as Mg$^{2+}$, Zn$^{2+}$, Ni$^{2+}$, Sc$^{3+}$), B2 is a high valence cation (such as Nb$^{5+}$,Ta$^{5+}$, W$^{6+}$) with complex perovskite (ABO$_3$) structure. Lead Titanate PbTiO$_3$ (PT) has largest polarization among the perovskites and is an indispensable compound having large dielectric and piezoelectric properties. Such a solid solutions of Pb(B$_1$, B$_2$)O$_3$ - PT has Morphotropic phase boundary (MPB) separating the rhombohedral and tetragonal phases. It shows considerable electromechanical (e/m) coupling factors and dielectric constant due to suitable composition at MPB. The excellent piezoelectric properties make these crystals promising for medical ultrasonic, nondestructive testi! ng and undersea applications. Single crystals with appropriate orientation have high piezoelectric coefficient comparable to piezoelectric ceramic. This will help to replace ceramics presently used in transducers and in piezoelectric actuators. Single crystals of these materials have been grown by high temperature solution growth technique.

In the present study, high temperature solution growth (flux growth method) was adopted to grow 0.58Pb(Sc$_{1/2}$ Nb$_{1/2}$)O$_3$ - 0.42PbTiO$_3$ (PSNT) single crystals. Processing conditions have been optimized during the growth of bulk crystal, including cooling rate, soaking period and growth temperature. Crystalline nature has been confirmed by powder XRD studies. The crystalline quality and orientation was confirmed by Laue pattern. Dielectric studies for (001) crystal predicted the system has inherent relaxor property. The results will be discussed in detail.