Pyroelectric properties of ReCOB and BiBO oxyborate crystals with monoclinic symmetry

Pyroelectric properties of oxyborate crystals with monoclinic structure, including ReCa₄O(BO₃)₃ (ReCOB, Re: rare-earth elements) and BiB₃O₆ (BiBO), were investigated by charge integration method. The pyroelectric p₁ of ReCOB crystals was found to be negative, being on the order of -59.3~-65.5μC/(m²·°C) at 30°C, while the pyroelectric p₃ was determined to be positive, being around 11.6~31.0μC/(m²·°C). The pyroelectric coefficients p₁ and p₃ 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 (p₂) was obtained for BiBO crystals, being on the order of 105.0μC/(m²·°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 LiTaO₃.