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Srungarpu Nagabhusan Acharya) and Sadequa J. Patwe Chemistry Division, Bhabha Atomic Research Centre, Mumbai, India 400085

Ramasamy Jayavel Crystal Growth Centre, Anna University, Chennai, India 600025

Garamilla Mangamma and Ashok Kumar Tyagi Surface and Nanoscience division, Materials Science group, Indira Gandhi Centre for Atomic Research, Kalpakkam, India (Received 3 July 2013; accepted 1 April 2014)

The structure and phase transition behavior of monoclinic phase of the morphotropic phase boundary composition Pb(Sc1/2Nb1/2)O3]0.58 –[PbTiO3]0.42 (PSN–42PT) in lead scandium niobate–lead titanate (PSN–PT) system have been investigated by in situ high-temperature polarized light microscopy (PLM) and x-ray diffraction (XRD) studies. Temperature-dependent powder XRD studies of PSN–42PT indicated monoclinic structure at 25 °C and cubic structure at 400 °C. It is observed that the room temperature monoclinic structure transforms to cubic structure through an intermediate tetragonal structure. The temperature-induced domain changes at the phase transition are investigated on (001) face of unpoled PSN–42PT crystal while heating as well as cooling the crystal on hot stage of the PLM. Under crossed polar condition, the striplike polar domains observed at lower temperature vanish gradually with increasing temperature. In the vicinity of ferroelectric transition temperature, the mesosize domains that appeared in the variable temperature PLM images are in accordance with the monoclinic–tetragonal–cubic transition sequence concluded by in situ high-temperature XRD studies. The domain rotation corresponding to the structural transformation sequence is concluded for the first time in the PSN–42PT. I. INTRODUCTION

The observation of large piezoelectric responses near the Morphotropic Phase Boundaries (MPBs) of [Pb(Zn1/3Nb2/3)O3]1
x–[PbTiO3]x, lead zinc niobate– lead titanate (PZN–PT), [Pb(Mg1/3Nb2/3)O3]1
x–[PbTiO3]x, lead magnesium niobate–lead titanate (PMN–PT), and Pb (Zr1
xTix)O3,lead zirconate titanate (PZT) systems has drawn significant research attention to understand their physical origins.1–3 Investigations on (1
x)PZN–xPT, (1
x)PMN–xPT, and (1
x)PSN–xPT revealed that the MPB compositions exist as multiphase systems.1–9 Neutron and high-resolution synchrotron x-ray diffraction studies of Haumont et al.4 revealed the existence of an additional monoclinic (M) phase in addition to the known rhombohedral (R) and tetragonal (T) at the MPB composition range of (1
x)PSN–xPT (x 5 0.41–0.55).4 The influence of coexistence of R, M, and T phases on spontaneous polarization has also been discussed by the authors.4 Similar studies on PZN–xPT and PMN–xPT crystals a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.87 1054

J. Mater. Res., Vol. 29, No. 9, May 14, 2014

http://journals.cambridge.org

Downloaded: 14 Mar 2015

revealed coexistence of rhombohedral and tetragonal domains at room temperature (RT).10–12 However, later studies on these systems indicated the presence of a third