Dielectric, Impedance, and Modulus Spectroscopy Studies of KDP–K ₂ SO ₄ Composite Crystal System

Potassium dihydrogen phosphate (KDP) is a well‐known nonlinear optical (NLO) crystal with important applications in laser‐based and optoelectronic devices. In this work, KDP–K 2 SO 4 composite crystals were grown to tune their A.C. electrical properties. Since KDP and K 2 SO 4 have different crystal structures and solubilities in water, growing composite crystals is challenging. The crystals were prepared by mixing 50 mL of KDP solution with 75 mL of K 2 SO 4 solution, followed by stirring for 2 h and slow solvent evaporation at 27 °C. Transparent, colorless, and prismatic crystals were obtained, while pure KDP crystals were grown under similar conditions for comparison. Powder X‐ray diffraction confirmed the coexistence of tetragonal KDP as the major phase and orthorhombic K 2 SO 4 as the minor phase. EDAX analysis at three different regions further verified the composite nature through sulfur detection. A.C. electrical measurements were performed from 100 Hz to 10 MHz at 350, 400, and 450 K. The dielectric, impedance, modulus, and conductivity responses were analyzed. Jonscher's power‐law fitting suggested that conduction follows the correlated barrier hopping model. Nyquist and modulus analyses revealed dominant grain contribution, modeled using an R‐CPE equivalent circuit.