Anomalous electrical behaviour of single-crystal glycine near room temperature

Electrical impedance measurements of single-crystal glycine reveal anomalous temperature dependence of the conductance and capacitance. Upon cooling the crystal from 50 degrees C the conductance decreases smoothly from an initial value of 0.1 nS to about 0.02 nS at 31 degrees C. Further cooling, however, causes a dramatic increase in conductance with a magnitude approaching 100 nS at 21 degrees C. Similar anomalous behaviour is exhibited by the concurrently measured capacitance; it is approximately temperature independent above 31 degrees C but decreases precipitously below this temperature. This unusual electrical behaviour is not explained readily by the conduction mechanisms expected to apply to these materials but is consistent with the onset of pyroelectricity at 31 degrees C.