Radiation Damage and the Ferroelectric Effect in Rochelle Salt

Abstract

Rochelle salt 45° X‐cut square plates were exposed to Co⁶⁰ radiation of 8.6×10³ to 2.6×10⁷ R and reactor radiation up to 2.4×10⁶ R gamma plus 3.5×10¹⁵ neutrons/cm². Measurements were made over a temperature range including both Curie points (−30° to +30°C) of dielectric constant and loss, elastic stiffness coefficients c₄₄^D, and mechanical Q. In addition, double‐crystal x‐ray rocking curves were made above the upper Curie point to check line broadening. All the data indicate an initial improvement in crystal perfection (Curie points are sharper, linewidths narrower) up to 8.6×10⁴ R, with subsequent degradation (Curie point and linewidth broadening: finally coalescence of Curie points) including elimination of the ferroelectric phase after 2.6×10⁶ R Co⁶⁰ radiation or 2.4×10⁶ R gamma plus 3.5×10¹⁵ neutrons/cm² reactor radiation. The Q rose with radiation dosage as the ferroelectric phase disappeared, dropping only at the highest dosage. Destruction of the ferroelectric phase by radiation is compared to similar effects due to substitution of NH₄ for K in the Rochelle salt lattice.