Pyroelectric properties of rare-earth calcium oxyborate crystals: ReCa ₄O(BO₃)₃ (Re: Y, Gd, Nd, and Pr)

Pyroelectric properties of the monoclinic ReCa₄O(BO ₃)₃ (ReCOB, where Re is rare earth: Y, Gd, Nd, and Pr) single crystals were investigated by the charge integration method in the temperature range of 20°C to 180°C. The two independent pyroelectric coefficients p₁ and p₃ were measured and their temperature-dependent properties were studied; the pyroelectric p1 was found to be negative and decrease with increasing temperature, varying from -59.3, -64.2, -65.5, and -59.5 μC/(m^2·°C) at 30°C to -52.9, -53.3, -46.6, and -50.5 μC/(m^2·°C) at 180°C for YCOB, GdCOB, NdCOB, and PrCOB, respectively, whereas the positive coefficient p3 was observed to decrease from 11.6, 13.6, 23.5, and 31.0 μC/(m ^2·°C) at 30°C to 2.5, 7.1, 4.9, and 10.1 μC/(m ^2·°C) at 180°C, respectively. In addition, the ReCOB crystals were found to possess relatively high detectivity F_d, being 7.6 to 11.4 x 10^-5 Pa^-1/2 at 30°C, approximately two times that of commercial triglycine sulfate (TGS) and LiTaO₃ crystals, with minimal variations up to 180°C, indicating the potential for use in thermal imaging applications.