Anomalous pyroelectric behavior in the leaves of the palm-like plant encephalartos villosus

Quantitative pyroelectric measurements were made on the epidermis of the leaves of the palm-like plant Encephalartos Villosus. The average value of the pyroelectric coefficient was 0.0129 ± 0.0043 μC m-2 K-1 at 298 K, about two orders of magnitude smaller than that of tourmaline. Imposition of a dc bias electric field of 2.7 kV cm-1 increased the pyroelectric coefficients by a factor of between 10 and 50. Application of fields as great as 18.2 kV cm-1 did not reverse the polarity of the samples, proving that the material is not ferroelectric. The bias field-induced pyroelectric effect was explained by means of a non-linear theory. A stress-induced non-linear pyroelectric effect was also observed.