Journal of the Physical Society of Japan · 1965 · 83 citations · 11 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsSolid State PhysicsThermodynamicsFerroelectric MaterialsPhase TransitionsThermal Properties Of MaterialsThermodynamics Of NanomaterialsThermoelectric MaterialsFerroelectric CrystalsFerroelectric PropertiesHeatHeat CapacityMolar VolumeThermal ExpansionThermal Expansion Of CrystalsThermoelectric Properties
Phase transitions of ferroelectric NaNo 2 crystal around 164°C were studied by calorimetric and dilatometric methods. The values of both heat capacity and molar volume show an abrupt increase at about 163°C, indicating that this transition is of the first order. In the region of 164∼165°C, a small broad peak was observed in the C p – T curve. On the other hand there appear two small anomalies in the volume expansion curve at 164.2°C and 164.7°C respectively. The total entropy of transition amounts to 1.26±0.08 e. u., which is nearly equal to R 1n2=1.377 e. u., and suggests that the orientational order of NO 2 - ions is destroyed completely in the paraelectric phase.
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