Synthesis, crystal structure and thermal behavior of Na4[B10O16(OH)2]·4H2O

New hydrated sodium borate Na4[B10O16(OH)2]·4H2O has been synthesized under mild hydrothermal conditions at 170 °C. The structure was determined by single-crystal X-ray diffraction and further characterized by FT-IR, Raman spectra and DTA-TG. It crystallizes in the monoclinic space group Pc with a unit cell of dimension a = 11.323(2) Å, b = 6.5621(14) Å, c = 12.244(3) Å, α = 90°, β = 91.050(3)°, γ = 90°, V = 909.7(3) Å3, Z = 2. The crystal structure of Na4[B10O16(OH)2]·4H2O consists of Na–O polyhedra and [B10O16(OH)2]4− polyborate anions. Dehydration of this compound occurs in three steps and leads to an amorphous phase which undergoes crystallization.