Photoconductivity and dielectric studies on NLO active NPNa and NPLi single crystals

Single crystals of efficient nonlinear optical materials, sodium p-nitrophenolate dihydrate (NPNa) and lithium p-nitrophenolate trihydrate (NPLi) have been successfully grown by slow evaporation technique. The qualitative SHG measurements by Kurtz powder show high value of deff for these crystals as compared to KDP and lithium niobate. Photoconductivity studies reveal that the photocurrent (IP) increases linearly with applied field E (V/cm) for both the crystals. However, for NPNa, the photocurrent is prominent due to the photoactive centers formed by Na+ ions with trap energy level. Dielectric behaviour of these crystals show very low value of dielectric constant at higher frequencies and increases their possibilities towards NLO device applications. The electrical conductivity is ionic in nature and found to be 1.26 × 10−5 mho m−1 for NPNa and 7.04 × 10−7 mho m−1 for NPLi, respectively.