Phase transitions in Cs2CdI4 single crystals

Abstract

Cs2CdI4 crystals are grown from the melt (A) and from water solution (B). Optic, dielectric, X‐ray, and calorimetric investigations are carried out. Crystal A shows three phase transitions at 332.3, 259.6, and 183.4 K with following sequence of phases: commensurate orthorhombic of β‐K2SO4 type (a0 = 1.074, b0 = 0.8458, c = 1.4852 nm) ↔ incommensurate ↔ monoclinic ferroelastic (P21n) ↔ triclinic ferroelastic (P1). The B‐crystal belongs to monocline symmetry (P21/m) and undergoes transformation into the orthorhombic phase of β‐K2SO4 type at ≈ 420 K.

A133Cs NMR Spin-Lattice Relaxation Study in Incommensurate Cs2CdI4

“…DTA thermograms measured on heating displayed endothermic anomalies due to phase transitions at 183 ± 1, 259.3 ± 0.6 and 331.6 ± 0.7 K, in good agreement with the reported transition temperatures, Tc,T c and T ]C [4,10,11], respectively.…”

“…The N and C phases were shown to be isomorphous with corresponding phases in Cs 2 HgBr 4 [6], while a modulation wave vector in the IC phase (qr IC ~ 0.26a*) [4] is different from that in the bromo compound (q lc ~ 0.15a*) [7],…”

“…In this compound, the dynamics of the IC phase modulation wave could also be described by the classical planewave-approximation in all temperature range of the IC phase [3], In the present study, we selected Cs 2 CdI 4 , reported to form an IC phase below 259.6 K [4], and intended to reveal the mechanism of the N-IC phase transition by comparing NMR results with those obtained for Cs 2 CdBr 4 and Cs 2 HgBr 4 [3].…”

“…B undergoes no phase transition below room temperature but transforms to A at ca. 420 K. On the other hand, A undergoes successive phase transitions [4]:…”

Fast intrinsic emission in single crystal

“…In the previous studies of this crystal main attention was focused on investigation of the structural phase transitions (Aleksandrov et al, 1988;Melnikova and Primak, 1992) and impurity luminescence (Bolesta and Furgala, 1991). The Cs 2 CdI 4 crystal possesses the phase transitions at 332.4, 259.6 and 183.5 K.…”