Thermodynamic properties for two mixed alkaline earth-transition metal borates of BaZn2B2O6 and Ba2Cd(B3O6)2

Abstract

Two alkaline-earth metal borates BaZn2B2O6 with NLO property and Ba2Cd(B3O6)2 with birefringent property have been synthesized and characterized by XRD, FT-IR, and chemical analysis. The molar enthalpies of solution of BaZn2B2O6 (s) and Ba2Cd(B3O6)2(s) in 2.00 mL of 1 mol·dm−3 HCl(aq) were measured by microcalorimeter at T = 298.15 K, respectively. The molar enthalpies of solution of CdCl2·2.5H2O(s) and ZnO(s) in the mixture solvent of 2.00 mL of {1 mol·dm–3HCl + H3BO3 + Ba(OH)2·8H2O} (aq) were also measured, respectively. With the incorporation of the previously determined enthalpies of solution of H3BO3 (s) in 2.00 mL of 1 mol· dm–3HCl (aq), Ba(OH)2·8H2O) in the mixture solvent of (2.00 mL of 1 mol·dm−3 HCl + H3BO3) (aq), together with the standard molar enthalpies of formation for CdCl2·2.5H2O(s)/ZnO(s), Ba(OH)2·8H2O(s), H3BO3(s), HCl (aq) and H2O (l), the standard molar enthalpies of formation of – (2703.0 ± 2.2) kJ·mol−1 for BaZn2B2O6 (s) and – (5625.26 ± 5.1) kJ·mol−1 for Ba2Cd(B3O6)2 at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.