Lefkowitz precursor investigations of barium sodium niobate

I. Lefkowitz wrote four papers on Ba2NaNb5O15 (BSN) between 1969 and 1971. We show that these papers contained the roots of a wealth of interesting physical results later investigated in detail, namely, the existence of incommensurate phases in BSN, the occurrence of a complex lattice dynamics with overdamped and underdamped soft modes as well as a critically narrowing central peak, and the probable occurrence of a strong interplay between local defects and a long-range order-parameter.