Copper sublattice ordering in layered CuMP2Se6 (M=In, Cr)

Piezoelectric and elastic properties of layered materials of Cu(In,Cr)P2(S,Se)6 system

“…Calorimetric evidence for the occurrence of a broad phase transition between 220 and 240 K in this compound was given in [7]. A single-crystal X-ray diffraction study showed that the high-and lowtemperature structures of CuInP 2 Se 6 (trigonal space group P-31c and P31c, respectively) are very similar to those of CuInP 2 S 6 in the paraelectric and ferrielectric phases, with the Cu I off-centering shift being smaller in the former than in the latter [7]. Both cell parameters a and c slightly increase on cooling, only at T=226 K a parameters show a local minimum.…”

Broadband dielectric spectroscopy of CuInP2Se6 crystals

“…The results followed to the conclusion that an incommensurate phase occurs between T i and T c . However, the calorimetric investigations showed only a broad phase transition between 220 and 240 K in this compound [8]. More accurate broadband dielectric investigations showed only nearly second order phase transition at T c =226 K [9].…”

“…More accurate broadband dielectric investigations showed only nearly second order phase transition at T c =226 K [9]. From a single-crystal X-ray diffraction study follows that the high-and low-temperature structures of CuInP 2 Se 6 (trigonal space group P-31c and P31c, respectively) are very similar to those of CuInP 2 S 6 in the paraelectric and ferrielectric phases, with the Cu I off-centering shift being smaller in the former than in the latter [3,8]. There the thermal evolution of the cell parameters of CuInP 2 Se 6 was obtained by full profile fits to the X-ray diffractograms.…”

“…Evidently, for this reason the copper ion sites in the low-temperature phase of CuInP 2 Se 6 are displaced only by 1.17Å [8] from the middle of the structure layers in comparison with the corresponding displacement 1.6Å for CuInP 2 S 6 [1]. These facts enable to assume that the potential relief for copper ions in CuInP 2 Se 6 is shallower than for its sulphide analog.…”

Ultrasonic and piezoelectric studies of new layered ferroelectric compounds of Sn2P2S6 family

“…8,9 CuInP 2 Se 6 layered crystals also are non-compensated ferrielectrics with two cation sublattices (indium and cooper). 10,11 In CuInP 2 Se 6 compounds the first order PT at T c2 ≈ 236 K and second order PT at T c1 ≈ 249 K (the symmetry reduction P31c ↔ P31c at the PT) was observed. 12 The layered crystalline plates of SnP 2 S 6 belong to R3 symmetry group, which is preserved until melting temperature.…”