  We have recently analyzed theoretically the main characteristics of the edge
depolarizing electric field (EDEF), in the vicinity of a non-polar face of a
pyroelectric. In this work we measured and characterized the EDEF, excited by a
harmonical thermal wave. We present here experimental results obtained on a
pyroelectric crystal LiTaO3, confirming our theoretical predictions. We present
the theoretical analysis and description of the thermal wave and the induced
harmonically varying EDEF. The calculations assume an equivalent circuit of a
pyroelectric capacitive current source. The measured magnitude of the EDEF and
its spatial variation agree well with the theoretical model. The effect of the
air pressure at the pyroelectric/air interface, on the EDEF, was determined in
the interval 10^3 - 10^-6 torr. We found that EDEF increases significantly with
decreasing air pressure, presumably due to diminishing of adsorption screening
at the polar faces. Teflon plates, covering the polar faces, prevent
accumulation of screening charged particles, resulting in a drastic increase of
EDEF.
