Comments on the paper "Insight on the growth and property studies of inorganic hydrated borate (Na6[B4O5(OH)4]3·8H2O) single crystal ̶ An effective third order nonlinear optical (NLO) material for optical limiting application".

The authors of the title paper (Mater. Chem. Phy. 205 (2018) 138–146) claimed to have grown for the first time a new alkali metal borate with formula Na 6 [B 4 O 5 (OH) 4 ] 3 ·8H 2 O (I) by slow evaporation of an aqueous solution containing NaOH, H 3 BO 3 and C 3 H 4 O 4 in 3:1:1 mol ratio. In this letter to the Editor, many points of criticism concerning the crystal growth, structure characterization and interpretation of the spectral and thermal data of I are described to prove that it is improperly characterized. The most intense line in the powder pattern of tincalconite is the (303) reflection. [Display omitted] • Crystal growth of Na 6 [B 4 O 5 (OH) 4 ] 3 ·8H 2 O (I) is critiqued. • Experimental data of I are inconsistent with the proposed formula. • I is an improperly characterized material. [ABSTRACT FROM AUTHOR]