ON THE DISCOVERY OF THE DIELECTRIC RELAXATION AND FERROELECTRICITY IN Pb-CONTAINING COMPLEX PEROVSKITES

In the end of 1940s young soviet scientist Georgii Smolenskii discovered ferroelectric properties in lead titanate (PbTiO 3) [1] and found an anomaly in the temperature dependence of the dielectric constant in lead zirconate (PbZrO 3) [1,2]. This encouraging result was also independently obtained by G. Shirane [3] and G. Roberts [4]. Based on this data, Smolenskii came to the conclusion that Pb 2+ ions are essential for the appearance of ferroelectricity in perovskite-type materials, i.e., that they are " ferroelectrically active ". However, it was clear from the very beginning that the number of simple perovskites is very limited. So, only few new ferroelectric materials could be obtained. At the same time, some reports on sintering ceramic samples of complex perovskites with different ions in the octahedral positions appeared in literature. These ceramics were not ferroelectric and contained Ba 2+ and Sr 2 ions. Probably, these two observations stimulated Smolenskii to sinter first Pb-containing complex perovskites where ferroelectric state could apparently be expected. This conclusion was probably drawn already in 1953-54, since in his 1954 scientific report the principles of sintering of such compounds were already formulated. During these years, Smolenskii worked in the Institute for Chemistry of Silicates of the Academy of Science of the USSR on his second scientific degree (Doctor of Sciences). In fact, experimental work on complex perovskites started as early as 1956. At this time, several new young researchers just entered his laboratory. This allowed intensifying research work in this area greatly. However, at that moment some technical problems arose due to the move of the laboratory to the Institute of Semiconductors that was newly established in Leningrad. The relocation to a new place somehow hampered the experimental work and took a lot of time and effort. In spite of these problems, the first compounds including PbNi 1/3 Nb 2/3 O 3 (PNN) and PbMg 1/3 Nb 2/3 O 3 (PMN) were successfully sintered and investigated by the end of 1957 already. At this time, it was thought that the latter