Comment on “Structural, dielectric, optical and ferroelectric property of urea succinic acid crystals grown in aqueous solution containing maleic acid” by B.K. Singh et al. [J. Phys. Chem. Solids 71 (2010) 1774]

The volume of elementary cell of the urea succinic acid (M–USA) growing from a solution containing 1 mol% maleic acid is 69% greater than that of urea succinic acid (USA) grown in the usual conditions. M–USA crystallises in the monoclinic system with a centre of symmetry, which excludes the piezoelectric and ferroelectric properties. The results presented in the paper commented on are artefacts.