The enthalpies of formation, heat content, heat capacity, and transition of NaMgF3perovskite have been determined. A new high temperature calorimetric methodology has been applied for the enthalpy of formation measurements. The heat content and heat of formation measurements were done using a "hybrid calorimeter" built recently in our laboratory. For the heat capacity measurements, a Netzsch 404 high-temperature differential scanning calorimeter (DSC) has been used. The enthalpy of formation from the binary fluorides at 298 K is -15.76±2.46 kJ/mol, and that from the elements is -1716.51±2.8 kJ/mol. The measured heat capacities between 313 and 1153 K show aλ-anomaly with a transition at 1051 K. The presence of one peak supports a recent X-ray study which concluded that the crystal structure transforms from the orthorhombicPbnmphase directly to the cubicPm3mphase. The enthalpy of transformation is 2.3±0.03 kJ/mol. The heat content values measured by transposed temperature drop calorimetry are in agreement with those calculated by graphical integration of the experimental heat capacity data obtained by DSC.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry