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

Two alkaline-earth metal borates BaZn 2 B 2 O 6 with NLO property and Ba 2 Cd(B 3 O 6 ) 2 with birefringent property have been synthesized and characterized by XRD, FT-IR, and chemical analysis. The molar enthalpies of solution of BaZn 2 B 2 O 6 (s) and Ba 2 Cd(B 3 O 6 ) 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 CdCl 2 ·2.5H 2 O(s) and ZnO(s) in the mixture solvent of 2.00 mL of {1 mol·dm –3 HCl + H 3 BO 3  + Ba(OH) 2 ·8H 2 O} (aq) were also measured, respectively. With the incorporation of the previously determined enthalpies of solution of H 3 BO 3 (s) in 2.00 mL of 1 mol· dm –3 HCl (aq), Ba(OH) 2 ·8H 2 O) in the mixture solvent of (2.00 mL of 1 mol·dm −3 HCl + H 3 BO 3 ) (aq), together with the standard molar enthalpies of formation for CdCl 2 ·2.5H 2 O(s)/ZnO(s), Ba(OH) 2 ·8H 2 O(s), H 3 BO 3 (s), HCl (aq) and H 2 O (l), the standard molar enthalpies of formation of – (2703.0 ± 2.2) kJ·mol −1 for BaZn 2 B 2 O 6 (s) and – (5625.26 ± 5.1) kJ·mol −1 for Ba 2 Cd(B 3 O 6 ) 2 at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.