Anomalies of dielectric, elastic and electromechanical properties of K0.25(NH4)0.75H2PO4 single crystal in the vicinity of antiferroelectric phase transition

The dielectric permittivities (epsilon(11) and epsilon(33)), elastic compliance (S-66) and piezoelectric constant (d(36)) for the K-0.25( NH4)(0.75)H2PO4 single crystal were studied near antiferroelectric phase transition temperature (T-N). It was found that diffused maximums in both the epsilon(11)(T) and the epsilon(33)(T) dependences as well as in the d(36)(T) dependences are observed above T-N, while narrowed peak in S-66(T) curve is located below T-N. Analysis of experimental results speaks in favor of two-stage AFE -> PE phase transition in the crystal under study. Below T-N the drastic decreasing of electromechanical coupling factor (k(36)) is found. (c) 2013 Elsevier Ltd. All rights reserved.