On the phase transition in foreign phase inclusions in CsH2AsO4, KD2PO4, and KH2PO4 crystals

The low-frequency internal friction Q(-1) and the shear modulus G in a paraelectric phase of CsH2AsO4, KD2PO4, and KH2PO4 ferroelectrics were studied using a reversed torsion pendulum method. Anomalies in the Q(-1)(T) and G(T) dependences were observed above the Curie temperatures of these crystals, at temperatures 308, 253, and 293 K, respectively. The anomalies were associated with a first-order phase transition ((4) over bar 2m --> mm2) occurring in the foreign phase inclusions. (C) 2000 MAIK "Nauka/Interperiodica".