Potassium carbonate (K2CO3) as a new additive was added into the potassium dihydrogen phosphate (KDP) solutions in different molar ratios. The metastable zone width of KDP solution with 5 M% K2CO3 was determined and compared with the pure system. A good-quality KDP crystal with 5 M% K2CO3 additive was grown by the slow cooling method from aqueous solution by the rotation of the seed crystal with the in-house built rotation assembly. Dielectric measurements were carried out on pure and doped KDP crystals at various temperatures ranging from 313 to 423 K by the conventional parallel plate capacitor method, and it indicates that 5 M% K2CO3 addition leads to low dielectric constant value dielectrics. The addition of 5 M% K2CO3 and proper rotation of seed crystal (40 rpm) improves the quality of the crystal. The high-resolution X-ray diffractometry (HRXRD) analysis shows that the crystalline perfection of the crystal grown in these optimum conditions is extremely good without having any internal structural grain boundaries and mosaic nature. The crystals grown by these optimum conditions show positive effects in the various characterization techniques. The effect of additive on the growth, nucleation kinetics, structural, nonlinear optical, laser-induced damage threshold and optical properties have been investigated by the studies on pure and K2CO3-doped (in different concentrations viz., 1, 5 and 10 M%) KDP crystals grown under identical conditions. (C) 2008 Elsevier B.V. All rights reserved.