Thermochemical properties of two mixed alkali-alkaline earth metal borates with NLO properties for NaCaBO3 and Li4CaB2O6

Two alkali-alkaline earth metal borates with NLO properties for NaCaBO3 and Li4CaB2O6 have been synthesized and characterized by XRD, FT-IR, and chemical analysis. The molar enthalpies of solution of NaCaBO3 (s) and Li4CaB2O6 (s) in 2.00 cm3 of 1 mol·dm−3 HCl (aq) were measured by microcalorimeter at T = 298.15 K, respectively. The molar enthalpies of solution of CaCl2·2H2O(s) in the mixture solvent of 2.00 cm3 of (1 mol·dm−3 HCl + H3BO3 + NaCl) (aq), and {2.00 cm3 of 1 mol·dm−3 HCl + H3BO3 + LiCl·H2O} (aq) were also measured, respectively. With the incorporation of the previously determined enthalpies of solution of H3BO3 (s) in 2.00 cm3 of 1 mol·dm−3 HCl (aq), NaCl (s) in the mixture solvent of (2.00 cm3 of 1 mol·dm−3 HCl + H3BO3) (aq) and LiCl·H2O(s) in the mixture solvent of {2.00 cm3 of 1 mol·dm−3 HCl + H3BO3} (aq), together with the standard molar enthalpies of formation for CaCl2·2H2O (s), NaCl(s)/LiCl·H2O (s), H3BO3 (s), HCl (aq) and H2O (l), the standard molar enthalpies of formation of - (1664.5 ± 0.9) kJ·mol−1 for NaCaBO3 (s) and - (3391.7 ± 1.9) kJ·mol−1 for Li4CaB2O6 (s) at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.