STRUCTURAL RESPONSE OF KTIOPO4 TO ELECTRIC-FIELDS - EFFECTS DUE TO LOW-FREQUENCY MODULATION

A 290 mum slice of z-cut, flux-grown, KTiOPO4 was subjected to square-wave electric field modulation at 1 Hz and examined using synchrotron radiation and a differential energy-dispersive x-ray spectroscopy system. Asymmetric Laue reflections (h0h and h0hBAR) revealed the development of normally forbidden reflections (h odd) whose intensities grew until a threshold field of about 70 V/mm was reached, above which they disappeared. This effect was reversible and is interpreted as due to field-induced K+ ion disorder followed by domain reversal above a critical field with subsequent ordering. Symmetric Bragg reflections (00l) showed a dramatic effect: after a period of modulation, also at about 70 V/mm, the intensities began to fall and, at the same time, the peak widths began to narrow. This behavior resembles the transition from an ideally imperfect to an ideally perfect crystal and suggests that the crystal has been annealed electrically.