The pyroelectric effect and domain structure of heat-treated (Li2O out
diffused) LiNbO3 crystals have been studied. The heat treatment causes
a domain inversion and almost total suppression of the pyroelectric c
urrent. Non-inverted domains have been observed in the outdiffused inv
erted layer. Based on the pyroelectric current-temperature dependence
it is suggested that these domains are switched by an intrinsic bulk p
yroelectric field.