Temperature dependence Raman spectroscopic studies of Pb(Yb 0.5 Ta 0.5 )O 3 Dibyaranjan Rout a,1 , V. Subramanian a, * , V. Sivasubramanian b a Microwave Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India b Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India Received 28 February 2007; received in revised form 13 August 2007; accepted 17 August 2007 Available online 21 August 2007 Abstract The lead-based complex perovskite Pb(Yb 0.5 Ta 0.5 )O 3 , exhibiting long-range B-site cation ordering has been studied by Raman spectroscopy. The investigation has been performed as a function of temperature ranging from 250 K to a lower temperature 10 K in the spectral range 1020– 20 cm 1 . The spectra are analyzed through the characteristic parameters: peak position and line width of phonon modes. Significant decrease in the asymmetric phonon line broadening with noticeable shift of the peak positions and appearance of new modes in the Raman spectra at low temperature have been observed. The local distortion in the lattice has been enhanced substantially at low temperature. The splitting of the F 2g modes suggests that the orthorhombic phase is stabilized at low temperature. The two F 2g modes (60 and 518 cm 1 ) show soft mode behavior. # 2007 Elsevier B.V. All rights reserved. Keywords: Antiferroelectric materials; Ceramics; Raman spectroscopy 1. Introduction A lot of attention has been given to the lead-based complex perovskites for several years from the theoretical, experimental and industrial application points of view. Besides being beneficial for a variety of applications, e.g. capacitors, piezoelectric transducers, electrostrictive actuators and pyro- electric detectors, these materials are of keen interest from a fundamental point of view (structure and phase transition, inductive properties, non-linear optical properties, photo refractivity and electrochemical properties) [1,2]. Depending on the degree of order in the B-cation sublattice, these materials can be tentatively grouped into disordered (coherence length below 2 nm), short-range order (coherence length between 2 and 50 nm) and long-range order (coherence length above 100 nm) materials. It has been confirmed in many cases that the degree of order has a strong influence on the dielectric properties and related phase transition phenomena [3]. There are several factors that influence the B-site ordering such as: (a) the chemical valence and ionic difference between B 0 and B 00 cations and (b) chemical nature of A-site atoms. In this context the ordered perovskites are found to be highly sensitive to the heat treatments during sintering process. Specifically, the materials like Pb(Sc 1/2 Ta 1/2 )O 3 (PST), Pb(In 1/2 Nb 1/2 )O 3 (PIN) and Pb(Yb 1/2 Nb 1/2 )O 3 (PYN) undergo a change in the order parameter easily by different heat treatments and therefore attracts lot of attention for last few decades [4–6]. Lead ytterbium tantalate, Pb(Yb 1/2 Ta 1/2 )O 3 (PYT) is an antiferroelectric similar to highly ordered perovskites PYN and Pb(Ho 1/2 Nb 1/2 )O 3 (PHN) [7,8]. It undergoes two successive phase transitions: a sharp first order phase transition from paraelectric (PE) to antiferroelectric (AFE) at high temperature (=289 8C) and a diffuse phase transition from AFE to ferroelectric (FE) at low temperature (175 8C) [7]. The high temperature PE phase symmetry is cubic with space group Fm ¯ 3m, whereas the low temperature FE phase symmetry is interpreted as orthorhombically distorted ABO 3 type subcells with the pseudo-monoclinic cell and the space group at AFE and FE phase is considered as Pbnm [9–11]. The articles that have been published so far on PYT report the existence of super-lattice reflections which suggests the ordering in the www.elsevier.com/locate/vibspec Vibrational Spectroscopy 46 (2008) 22–27 * Corresponding author. Tel.: +91 44 2257 4883; fax: +91 44 2257 4852. E-mail addresses: dibyaranjanr@yahoo.co.in (D. Rout), manianvs@iitm.ac.in (V. Subramanian). 1 Present address: Materials Interface Laboratory, Department of Materials Science and Engineering, KAIST, 373-1 Guseong, Yuseong-gu, Daejeon 305- 701, Republic of Korea. 0924-2031/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.vibspec.2007.08.003