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The following article is a personal, and probably self-indulgent, review of the development of the classification of tilted octahedra in perovskite structures and my role in it. This review is not intended to be a thorough account of the topic, which has in any case been covered elsewhere, but is offered as a historical account of how the description of perovskite tilt systems in use today originally came about. [ABSTRACT FROM AUTHOR]

The present paper reports on the observation of the optical birefringence as a function of temperature of the langbeinite-type crystal K[SUB2]Mn[SUB2](SO[SUB4])[SUB3] by using an imaging version of the so-called rotating-polarizer method. This method provides separates moving images of the orientation of the optical indicatrix and the magnitude of the optical anisotropy, showing the domain-wall behaviour during temperature changes. Somenew results o the domain behaviour of the phase transition of K[SUB2]Mn[SUB2](SO[SUB4])[SUB3] have been obtained. It is concluded that the sample single crystal consists of local regions, indicating the coexistence of two phases in this langbeinite-type crystal. [ABSTRACT FROM AUTHOR]

Investigates the room-temperature crystal structure of the perovskite lead hafnate PbHfO[sub 3]. Use of low-temperature single crystal X-ray diffraction and polycrystalline neutron diffraction; Difficulties in determining the oxygen positions.

In 1947 Kathleen Lonsdale conducted a series of experiments on X-ray diffraction using a divergent beam external to a crystal sample. Unlike the Kossel technique, where divergent X-rays are excited by the presence of fluorescing atoms within the crystal, the use of an external divergent source made it possible to study non-fluorescing crystals. The resulting photographs not only illustrated the complexity of X-ray diffraction from crystals in a truly beautiful way, but also demonstrated unprecedented experimental precision. This long-forgotten work is repeated here using a synchrotron radiation source and, once again, considerable merit is found in Lonsdale's technique. The results of this experiment suggest that, through the use of modern 'third-generation' synchrotron sources, divergent-beam diffraction could soon enjoy a renaissance for highprecision lattice-parameter determination and the study of crystal perfection. [ABSTRACT FROM AUTHOR]