Dielectric Relaxation in Strontium Titanates Containing Rare-Earth Ions

Abstract

Ceramic samples of SrTiO₃, containing a wide range of solid substitution of trivalent rare‐earth ions, have been fabricated and examined in detail. Well‐developed dielectric relaxation was observed in samples containing lanthanum, praesodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, but not in samples containing cerium or europium. The relaxation occurs at normal low radio frequencies (10²−10⁵ Hz) in the temperature range −150° to +40°C, and there is a systematic variation of the relaxation parameters with both concentration and ionic size of the substituted ion. X‐ray and density measurements confirm that as with lanthanum [T. Y. Tien and L. E. Cross, Jap. J. Appl. Phys. 6, 459 (1967)]. and bismuth [G. I. Skanavi, I. A. M. Ksendzov, V. A. Trigubenko, and V. G. Prokhvatilov, Sov. Phys. JETP 6, 250 (1959)] substitutions, two rare‐earth ions and an associated vacancy substitute for three strontium ions in the ``A'' sites of the perovskite lattice. Possible explanations for the dielectric behavior are considered and it is shown that the data are consistent with an ionic model proposed earlier by Skanavi. [G. I. Skanavi and E. N. Matveeva, Sov. Phys. JETP 3, 905 (1957)].