Comments on the paper "Growth and optical studies of tris (thiourea) potassium barium sulphate crystal: a novel semiorganic NLO bimetallic crystal"

ABSTRACTIn a recent paper Azhar et al., (Mater. Res. Innov. https://doi.org/10.1080/14328917.2017.1392694) claim to have grown a tris (thiourea) potassium barium sulphate (TTPBS) crystal, which according to them is a novel NLO bimetallic crystal. In this comment, we prove that the so called TTPBS is a dubious crystal. In addition, we show that the so called barium thiourea chloride (Raju et al Mater. Res. Innov, 2016) thiourea barium chloride (Mahendra et al Optik 2017) and calcium bis(thiourea) chloride (Anis et al Optik 2016) single crystals are all dubious materials and do not contain any alkaline-earth metal but are simply thiourea.