Pyroelectric properties of ReCOB and BiBO oxyborate crystals with monoclinic symmetry

Pyroelectric properties of oxyborate crystals with monoclinic structure, including ReCa
₄
O(BO
₃
)
₃
(ReCOB, Re: rare-earth elements) and BiB
₃
O
₆
(BiBO), were investigated by charge integration method. The pyroelectric p
₁
of ReCOB crystals was found to be negative, being on the order of -59.3~-65.5μC/(m
²
·°C) at 30°C, while the pyroelectric p
₃
was determined to be positive, being around 11.6~31.0μC/(m
²
·°C). The pyroelectric coefficients p
₁
and p
₃
for ReCOB crystals were observed to decrease with increasing temperature, with variations being on the order of -10.8% to -79.1% over the test temperature range of 20~180°C. Comparing with ReCOB crystals, larger pyroelectric coefficient (p
₂
) was obtained for BiBO crystals, being on the order of 105.0μC/(m
²
·°C) at room temperature, maintaining the similar value up to 180°C. Of particular interest is that ReCOB and BiBO crystals were found to possess relative high detectivity F
_d
, two to three times that of commercial TGS and LiTaO
₃
.