However, it can be seen that these values are minimum for the K2CO, added KDP with impurity concentration of 5M%. The values increase when concentration increases further. As the samples were the impurity annealed before making measurements this may not be due to the adsorbed water. Increase in K2CO3 concentration may lead to high density of induced bulk defect states due to competition in getting the interstitial sites for the K2CO3 molecules to occupy. Decrease in K2CO3 concentration may lead to high density of induced bulk interstitial sites. defect states due to availability of unoccupied A5M%may be the proper concentration for the K2Co3 molecules to occupy the available interstitial sites in the KDP crystal structure. This may be the reason for the complex situation observed with the above dielectric parameters in the present study. However, it is interesting to note that 5M% K2CO3 addition to KDP leads to a significant reduction of er value and consequently leads to low er value dielectrics, a knowledge gaining importance of late. Optical transmission