Studying the dielectric, electromechanical, and elastic properties of K1 − x(NH4)xH2PO4 mixed crystals
Temperature dependences of the longitudinal permittivity, piezoelectric coefficient d36, and elastic constant c66E of K1 − x(NH4)xH2PO4 mixed crystals are studied experimentally. A microscopic model is proposed for crystals of the K1 − x(NH4)xH2PO4 type that includes the piezoelectric contribution to the effective pseudospin cluster Hamiltonian. Dielectric elastic and electromechanical properties of these crystals with ammonium concentrations x below 0.40 are calculated in a wide temperature range using the cluster approach. The calculation results are in qualitative agreement with experimental data.