  Static charge in and on the surface of pyroelectric crystals of LiNbO3 and
LiTaO3 in a dilute gas has been shown to ionize gas molecules via electron
tunneling. The released electrons and positive ions are focused and accelerated
according to the sign of the static uncompensated charge. The uncompensated
charge is produced when the temperature of the crystal is changed from any
initial temperature between about 500K and about 15K. It may be either
polarization charge that is inside the crystal surface or compensation charge
that is on the surface. The direction of temperature change and the polarity of
the base of the crystal determine whether electrons or positive ions are
accelerated toward or away from the crystal. The ionization, focusing and
acceleration may continue for more than 15 days following a single change in
temperature.
