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Dielectric Studies of CN – Dipolar Reorientation and Order–Disorder Behavior in RbCN 1–x :KCN x and KCN 1–x :NaCN x
Author(s) -
OrtizLopez J.,
Luty F.
Publication year - 2001
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/1521-3951(200112)228:3<893::aid-pssb893>3.0.co;2-p
Subject(s) - antiferroelectricity , relaxation (psychology) , dielectric , dipole , neutron diffraction , materials science , phase (matter) , superposition principle , condensed matter physics , atmospheric temperature range , phase diagram , phase transition , crystallography , thermodynamics , chemistry , crystal structure , ferroelectricity , physics , psychology , social psychology , optoelectronics , organic chemistry , quantum mechanics
The evolution of phase transitions and CN — dipolar reorientation are studied in two mixed alkali‐cyanides RbCN 1— x :KCN x and KCN 1— x :NaCN x for 0 ≤ x ≤ 1 with dielectric constant and loss measurements in the frequency range 10 1 to 10 5 Hz from room temperature to 4 K. For RbCN 1— x :KCN x , transition into an CN — elastically ordered state occurs under cooling for all concentrations x , while CN — antiferroelectric ordering takes place only in the 0.50 ≤ x ≤ 1 range. For KCN 1— x :NaCN x , CN — elastic ordering takes place only close to the pure compounds (0 ≤ x ≤ 0.10 and 0.86 ≤ x ≤ 1), while in the remaining concentration range (0.10 ≤ x ≤ 0.86), CN — orientations freeze into a glass‐like disordered state at low temperatures. Antiferroelectric ordering is detected in this case only in the 0 ≤ x ≤ 0.06 and 0.86 ≤ x ≤ 1 ranges. Multiple dielectric relaxation phenomena are observed in the elastically ordered concentration regimes of KCN 1— x :NaCN x due to CN — reorientation occurring in different coexisting structural phases. Dielectric relaxation data for both mixed systems are modeled either with a single or a superposition of two or three Cole‐Cole type distributions of relaxation times. The obtained phase diagram for KCN 1— x :NaCN x disagrees with the one constructed from neutron powder diffraction because in that technique residual stresses introduced by sample grinding can modify the structure of phases.