Ferroelectrics, 339:209–218, 2006 Copyright © Taylor & Francis Group, LLC ISSN: 0015-0193 print / 1563-5112 online DOI: 10.1080/00150190600740192 Synchrotron Radiation Study of Structural Tendencies in Aurivillius Ceramics L. FUENTES, 1,∗ J. F. FERNANDEZ, 2 MA. E. FUENTES, 3 L. LASCANO, 4 M. E. VILLAFUERTE, 5 MA. E. MONTERO, 1 R. OLIVERA, 1 A. MEHTA, 6 AND T. JARDIEL 2 1 Centro de Investigaci´ on en Materiales Avanzados, Chih., M´ exico 2 Instituto de Cer´ amica y Vidrio, Arganda del Rey, Espa˜ na 3 Universidad Aut´ onoma de Chihuahua, Chih., M´ exico 4 Escuela Polit´ ecnica Nacional, Quito, Ecuador 5 Universidad Nacional Auton´ onoma de M´ exico, M´ exico 6 Stanford Synchrotron Radiation Laboratory, Stanford, USA A review of structural tendencies, as observed in several synchrotron radiation diffrac- tion studies of Aurivillius phases, is presented. The role of powder synchrotron radiation is analyzed. Investigated phases belong to Aurivillius families with n from 3 to 6, with partial substitution of small Ti cations and of large Bi cations. Representative formulas are: Bi 4 Ti 3−x W x O 12 , Bi n+1 Ti 3 Fe n−3 O 3n+3 and (Ba, Pb) 2 Bi 4 Ti 5 O 18 . Observed general behavior shows a tendency to increase disorder with increasing chemical complexity. The structure-polarization relationship in Ba 2 Bi 4 Ti 5 O 18 is investigated and a paradox between published results is highlighted. Synchrotron radiation results tend to confirm Lightfoots’s conclusions, suggesting electric polarization along the z axis. Keywords Synchrotron radiation; Aurivillius; crystal structure Introduction So-called Aurivillius ceramics show interesting ferroic characteristics. The crystal structure of the mentioned phases is formed by n (n = 1, 2, 3, . . . ) layers of perovskite octahedra, sandwiched between bismuth oxide layers. Structure-macroscopic properties relationships in Aurivillius ceramics have been re- sumed in [1]. The physical basis for discussing this topic is given by the Neumann’s Prin- ciple: Any macroscopic property’s point group contains the structural point group as a subgroup. One important (and sometimes forgotten) aspect of this Principle is the fact that different space groups, associated with the same point group, show no differences in their structure-macroscopic properties symmetry relationships. The well-known rule that prohibits centro-symmetrical crystals to be piezo- or ferroelectric is derived from the Neumann’s Principle. Another corollary, not always taken into account, is presented with the aid of Figs. 1 and 2. If a polarized system shows a mirror-symmetry plane, then the Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005; received for publication January 26, 2006. ∗ Corresponding author. E-mail: luis.fuentes@cimari.edu.mx [1895]/209