Crystal growth, structure and thermal properties of noncentrosymmetric single crystals PrCa4O(BO3)3

Noncentrosymmetric praseodymium calcium oxyborate single crystals, PrCa4O(BO3)3 (PrCOB), were grown by the Czochralski technique. The monoclinic unit cell parameters were found to be a = 8.177 Å, b = 16.157 Å, c = 3.629 Å and Z = 2 with space group Cm. Crystal density was measured using the Archimedes method, being on the order of 3.47 g cm−3. Thermal properties of PrCOB were investigated, where the specific heat was found to be 0.63 J g−1 °C−1 at room temperature, increasing to 0.85 J g−1 °C−1 at 700 °C. The thermal expansion coefficients were measured to be α11 = 7.99, α22 = 4.90 and α33 = 9.46 (10−6/°C), respectively. In addition, thermal diffusivity λ22 and thermal conductivity κ22 as a function of temperature were studied, where λ22 was observed to decrease from 0.89 to 0.58 mm2 s−1, while κ22 was found to maintain the same value, being ∼1.90 W m−1 °C−1 over the temperature range of 20–700 °C.