TY - JOUR
T1 - Optical studies of thermal cycling and hysteresis effects in elastic order-disorder phase transformations. I. Pure alkali-metal cyanide crystals
AU - Ortiz-Lopez, Jaime
AU - Luty, Fritz
PY - 1988
Y1 - 1988
N2 - The order-disorder transformations in NaCN, KCN, and RbCN are studied under thermal cycling around Tc by monitoring the change in optical transmission produced by the light-scattering properties of their multidomain ordered structures. The phase transitions in both NaCN (large-hysteresis cubic orthorhombic) and RbCN (hysteresis-free cubic monoclinic) remain basically unchanged under multiple thermal recycling. In contrast to these persistently ferroelastic (NaCN) and antiferroelastic (RbCN) ordering systems, KCN acts as a ''bistable'' borderline case at its critical temperature Tc168 K. After passing a large-hysteresis cubic orthorhombic transition in its first thermal cycle, a ''memory'' of it (preserved up to room temperature) causes, in all subsequent thermal cycles, hysteresis-free cubic monoclinic transitions at nearly the same Tc. When cooling beyond Tc, a gradual monoclinic → orthorhombic transition occurs around 155 K, which, under subsequent heating, returns with large (∼15 K) hysteresis back to the cubic structure. The well-correlated optical- and dielectric-constant changes of these transitions in KCN under various thermal-cycling conditions are presented and discussed.
AB - The order-disorder transformations in NaCN, KCN, and RbCN are studied under thermal cycling around Tc by monitoring the change in optical transmission produced by the light-scattering properties of their multidomain ordered structures. The phase transitions in both NaCN (large-hysteresis cubic orthorhombic) and RbCN (hysteresis-free cubic monoclinic) remain basically unchanged under multiple thermal recycling. In contrast to these persistently ferroelastic (NaCN) and antiferroelastic (RbCN) ordering systems, KCN acts as a ''bistable'' borderline case at its critical temperature Tc168 K. After passing a large-hysteresis cubic orthorhombic transition in its first thermal cycle, a ''memory'' of it (preserved up to room temperature) causes, in all subsequent thermal cycles, hysteresis-free cubic monoclinic transitions at nearly the same Tc. When cooling beyond Tc, a gradual monoclinic → orthorhombic transition occurs around 155 K, which, under subsequent heating, returns with large (∼15 K) hysteresis back to the cubic structure. The well-correlated optical- and dielectric-constant changes of these transitions in KCN under various thermal-cycling conditions are presented and discussed.
UR - http://www.scopus.com/inward/record.url?scp=0000358189&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.37.5452
DO - 10.1103/PhysRevB.37.5452
M3 - Artículo
SN - 0163-1829
VL - 37
SP - 5452
EP - 5460
JO - Physical Review B
JF - Physical Review B
IS - 10
ER -