Wan Q. Cao, Ling F. Xu, Mukhlis M. Ismail and Li L. Huang
the electron concentration and if the grain size is below 1 μm, diffusion of the defects from the grain boundary to the center may lead to enhanced insulation on the boundary under higher sintering temperature  . In order to better balance the non-stoichiometric effect caused by Nb doping, appropriate acceptor doping is seriously taken into account.
The development of BaTiO 3 -based high dielectric-constant-materials is necessary for potential applications  . Abdelkefi et al.  presented a detailed report on xNaNbO 3 –BaTiO 3 solid solution (x ranging
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. It is evident that doping of glycine has a positive impact on characteristic features of BTCF, BTCC, ZTS, ZTC and BTCA crystals [ 5 – 9 ]. Potassium thiourea chloride (PTC) crystal is a promising NLO material having a tetragonal structure, good optical transparency, moderate hardness and high thermal stability  . It is noteworthy that till date no doping attempt has been made in case of PTC crystal as well as no investigations were accomplished
to study the dielectric, third order nonlinear optical (TONLO) and surface characteristics of PTC crystal doped by an
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outer shell. Fortunately, bismuth (Bi) has high polarizability (>5 Å 3 ) [ 9 ]. Also, it is non-toxic and has no harmful effect on environment. Hence, Bi-based compounds seem to be the most likely replacement to the lead-based materials [ 6 , 10 ]. It is observed that among the Bi-based systems, (1 – x)(Bi 1/2 Na 1/2 )TiO 3 –xBaTiO 3 is considered to be one of the potential lead-free candidates for dielectric and/or piezoelectric applications. It exhibits a rhombohedral-tetragonal morphotropic phase boundary (MPB) around 0.06 ⩽ x ⩽ 0.08 with remarkable piezoelectric