JOURNALOF MATERIALS SCIENCE: MATERIALS IN ELECTRONICS 14 (2003) 463±469 Synthesis and characterization of Fe 3  -modi®ed PLZT ferroelectrics SOMA DUTTA, R. N. P. CHOUDHARY Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur-721301, India P. K. SINHA Department of Aerospace Engineering, Indian Institute of Technology, Kharagpur-721301, India Fe 3  -modi®ed nanocrystalline PLZT, i.e., Pb 0.92 [La 1  z Fe z ] 0.08 [Zr 0.60 Ti 0.40 ] 0.98 O 3 (PLFZT) z  0.0, 0.3, 0.6, 0.9, 1 materials were synthesized by a high-temperature solid-state reaction technique. X-ray studies of the compounds con®rmed the formation of single-phase, ultra®ne (nano-sized) and homogeneous materials. Microstructural scanning electron microscopy (SEM) study shows the uniform distribution of smaller grains on the surface of the samples. Detailed dielectric studies of the compounds as a function of temperature (30±450  C) show that the broadening of the permittivity peak and transition temperature depends on Fe 3  -ion concentration. Analysis of diffuseness g of the broadened dielectric peaks of the materials gave its value between 1 and 2, indicating the different degrees of substitutional disorder in the system. The increase in Fe 3  -substitution at the La-site of PLZT shows many interesting and unusual dielectric relaxor behaviors of the compounds. The transition temperature T c of PLZT (8/60/40) ferroelectric shifts towards a higher temperature region on increasing Fe 3  concentration. The variation of d.c. and a.c. electrical conductivity of the material with temperature shows its semiconducting behavior; and hence the materials can be used for some electronic devices. # 2003 Kluwer Academic Publishers 1. Introduction Nowdays, lead zirconate (PbZrO 3 )±lead titanate (PbTiO 3 ) solid solutions (hereafter PZT) are widely used as piezoelectric ceramics for wide industrial applications. It has been found that La-modi®ed PZT (usually called PLZT) with compositions closed to the morphotropic phase boundary (MPB) has very inter- esting and promising piezoelectric, pyroelectric, and other physical properties for device fabrication [1±5]. In most of the PLZT compounds or solid-solutions, broadened dielectric peaks or diffuse phase transitions and relaxor behavior have been observed [6]. A diffuse phase transition (DTP), in which the transition is smeared out over a certain temperature range (still having high dielectric constant), resulting in a gradual change in physical properties in the said temperature range. Our extensive studies show that substitution of monovalent alkali and trivalent rare-earth ions at the La-sites of PLZT has many interesting physical properties of the complex PLZT with different Zr/Ti ratios [7±11]. The complex PLZT materials were found to be more attractive for device applications [12±17]. As the smaller particle/crystallite size (nanometer) of the materials has a signi®cant effect on physical properties, recently, some attempts were made to synthesize nano-PZT/PLZT using high-energy ball milling [18] and other processing techniques [19]. Substitution of some ions at different atomic sites also plays an important role in reducing particle size. A detailed literature survey suggests that not much work has been done on trivalent (Fe, Sb, Bi, Al, and Ga) ions substituted (at La-site) into PLZT. To study the effect of the above trivalent ions on particle size, phase transition, and other physical parameters of PLZT, we have carried out systematic and extensive studies of structural, microstructure, dielectric, and electrical properties of trivalent-ion-substituted PLZT (La/ Zr/ Ti: 8/60/40) compounds. In this paper, we report the effect of Fe 3  ion substitution on the above properties of PLZT. 2. Experimental Nanocrystalline samples of [Pb 0:92 (La 1  z Fe z ) 0:08 ] [Zr 0:60 Ti 0:40 ] 0:98 O 3 (hereafter PLFZT) with z  0.0, 0.3, 0.6, 0.9, 1.0 were prepared by a high-temperature solid- state reaction technique using ingredient oxides: PbO (99.99%, M/S Aldrich Chemical Company Inc. USA), La 2 O 3 (99.9%, M/S Indian Rare Earth Ltd.), Fe 2 O 3 (98.5%, M/S Loba Chemie, Bombay, India), ZrO 2 (97%, M/S Loba Chemie, Bombay, India), TiO 2 (99.5%, M/S Loba Chemie, Bombay, India) in the required stoichio- metry. The reactive powders were thoroughly mixed in an agate mortar for 2 h and calcined at 1050  C for 7 h in 0957±4522 # 2003 Kluwer Academic Publishers 463