Pyroelectric Properties of Rare-Earth Calcium Oxyborate Crystals: ReCa4O(BO3)3 (Re: Y, Gd, Nd, and Pr)

Pyroelectric properties of the monoclinic ReCa4O(BO3)(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 degrees C to 180 degrees C. The two independent pyroelectric coefficients p(1) and p(3) were measured and their temperature-dependent properties were studied; the pyroelectric p(1) was found to be negative and decrease with increasing temperature, varying from -59.3, -64.2, -65.5, and -59.5 mu C/(m(2).degrees C) at 30 degrees C to -52.9, -53.3, -46.6, and -50.5 mu C/(m(2).degrees C) at 180 degrees C for YCOB, GdCOB, NdCOB, and PrCOB, respectively, whereas the positive coefficient p(3) was observed to decrease from 11.6, 13.6, 23.5, and 31.0 mu C/(m(2).degrees C) at 30 degrees C to 2.5, 7.1, 4.9, and 10.1 mu C/(m(2).degrees C) at 180 degrees 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 degrees C, approximately two times that of commercial triglycine sulfate (TGS) and LiTaO3 crystals, with minimal variations up to 180 degrees C, indicating the potential for use in thermal imaging applications.