Title: DIFFUSION PHASE TRANSITIONS IN (PB$_Y$SN$_{1-Y}$)$_2$P$_2$(SE$_X$S$_{1-X}$)$_6$ SOLID SOLUTIONS
Author(s): M.M.Maior, Sh.B.Molnar, V.T.Vrabel, M.I.Gurzan, S.F.Motrja, Yu.M.Vysochanskii (Institute for Solid State Physics and Chemistry, Uzhgorod National University, Uzhgorod, Ukraine)

The dielectric properties of (Pb$_y$Sn$_{1-y}$)$_2$P$_2$(Se$_x$S$_{1-x}$)$_6$ mixed crystals in the vicinity of the incommensurate phase transition have been studied. It has been found that due to the defect action, the dielectric anomalies at the phase transitions are smeared and instead of two anomalies bounding the incommensurate phase there is observed a single broad peak. The character of the dielectric dispersion as well as nonlinear dielectric behavior in the crystals studied suggest that in the chaotic state due to the action of the defect on the IC phase, the crystals possess the properties of ferroelectrics relaxors.

Key words: diffusion phase transition, relaxors, dielectric properties
PACS: 77.84.Dy, 77.80.Bh