Journal of the Physical Society of Japan · 1979 · 43 citations · 7 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsCrystal StructureSolid State PhysicsCrystal ChemistryCrystallographyPhase TransitionsThermal Expansion AnalysisThermal Properties Of MaterialsX-ray CrystallographyAnisotropic Thermal ExpansionAnisotropyLinear Thermal ExpansionPhase Transition TemperatureTemperature DependenceThermal ExpansionThermal Expansion ObservationThermal Expansion Of Crystals
Linear thermal expansions of (NH 4 ) 3 H(SO 4 ) 2 were measured both by an X-ray diffractometer and by a dilatometer in a temperature range between 100 K and 450 K covering the four phase transitions. The crystal exhibits a large anisotropy in the linear thermal expansion coefficients measured along the pseudo-orthorhombic a 0 , b 0 and c 0 axes. Of thermal expansion coefficients along the three axes, the coefficient observed near but above the transition temperature T c II (265 K) shows the largest anomalous temperature dependence along the c 0 axis. The coefficient observed near but above the transition temperature T c III (140 K), however, shows relatively large anomalies in the plane perpendicular to the c 0 axis.
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