Ferroelectricity: The foundation of a field from form to function

This article highlights the major role Arthur von Hippel and the Laboratory for Insulation Research at the Massachusetts Institute of Technology played in the early development of the field of ferroelectricity in mixed oxides with the perovskite structure and, in particular, in the identification of ferroelectricity in barium titanate following its discovery in industrial laboratories in the United States during World War II. Very early optical and x-ray studies highlighted the characteristics of the ferroelectric domain structures in both ceramic and singie-crystal BaTiO3, the elimination of domains at the Curie temperature T-C, and the salient characteristics of the two low-temperature phase transitions. Perhaps the culmination of this work was the detailed studies of lamella 90 degrees domains by Peter Forsbergh and the gorgeous patterns these could generate. This article also traces the manner in which the early studies contributed to whole industries based on perovskite ferroelectrics. The ceramic capacitor industry is now fabricating sophisticated, cofired multilayer capacitors (MLCs) with up to a thousand 1-mu m-thick dielectric layers interleaved with base metal electrodes, addressing a market for some 10(13) capacitors per year. Manufacturers of large piezoelectric transducers depend almost exclusively on perovskite-structure oxide ceramics. Navy sonar systems are major customers, but spinoff has occurred into a wide range of commercial and medical ultrasound systems. The capability of current materials has improved more than tenfold over the original BaTiO3 ceramics as a result of the effective application of molecular engineering, a strong testament to the insight of the founder of this area of study.