Piezoelectric crystals of neodymium calcium oxyborate, NdCa 4O(BO3)3 (NdCOB), were grown by the Czochralski technique. The density was measured using the Archimedes method and found to be 3.63 g/cm3, in good agreement with the theoretical value. The thermal properties of NdCOB have been investigated, with the specific heat being on the order of 0.550 J/(g C). The four thermal expansion coefficients were measured and found to be ±11 = 8.12, ±13 = 0.680, ±22 = 5.96, and ±33 = 10.3 (10 -6/C), respectively. The relative dielectric permittivities were determined to be e11T/e0 = 9.90, e22T/e 0 = 15.5, e33T/e0 = 10.2, and e13 T/e0 = -1.60, respectively, with corresponding low dielectric loss at 100 kHz, being on the order of <0.1%. The complete set of dielectric, elastic, and piezoelectric constants for NdCOB single crystals were determined by the resonance method and compared to other oxyborate crystals ReCa4O(BO3)3 (Re = rare earth), where NdCOB exhibited relatively higher piezoelectric properties with d13 = -4.8 pC/N, k13 = 16.8%, d26 = 16.5 pC/N, and k26 = 31.1%, respectively. The relationship between piezoelectric property and structure was explored, in order to further improve the properties of ReCOB crystals. © 2010 American Chemical Society.