Thermodynamic studies of the thermochromic phase transition in coordination compound of iron with triazole
- Inst. of Inorganic Chemistry, Novosibirsk (Russian Federation)
The aim of this work was to investigate the thermodynamic properties of nitrate tris(4-amino-1,2,4-triazole) iron(II) for which a thermochromic effect takes place at T=342 K on heating and at 310 K on cooling. For the measurement of the isobaric heat capacity in the 5--355 K range, a vacuum adiabatic calorimeter was used. Below 300 K, the C{sub p,m}(T) curve has no anomalies; the average deviation of the experimental heat-capacity values from the smoothed C{sub p,m}(T) curve was 0.1 percent. Above 300 K, the C{sub p,m}(T) curve shows a complicated behavior. The abnormal part of the heat capacity first increases smoothly, then from 330 K a sharp rise begins. There is a peak on the C{sub p,m}-curve at T=343.0 K. This fact is in a good agreement with the magnetic measurement data. The transition enthalpy was determined to be 22.8 kJ{center_dot}mol{sup {minus}1} (M=432.10 g{center_dot}-mol{sup {minus}1}). Further increase of the heat capacity suggests the existence of a new phase transition above 350 K. This suggestion was confirmed qualitatively by the measurements on a differential scanning calorimeter. It should be noted that on the low-temperature slope of the anomaly, at 320<330 K there is a small anomaly with the maximum deviation of 5--10 percent from the regular part. To compare the phonon characteristics, the heat capacity of nitrate tris(4-amino-1,2,4-triazole) copper(II) was studied.
- OSTI ID:
- 197607
- Report Number(s):
- CONF-950793-; ISBN 0-8194-1890-0; TRN: IM9612%%381
- Resource Relation:
- Conference: 40. annual meeting of the Society of Photo-Optical Instrumentation Engineers, San Diego, CA (United States), 9-14 Jul 1995; Other Information: PBD: 1995; Related Information: Is Part Of Optical materials technology for energy efficiency and solar energy conversion XIV; Lampert, C.M. [ed.] [Lawrence Berkeley Lab., CA (United States). Energy and Environment Div.]; Deb, S.K. [ed.] [National Renewable Energy Lab., Golden, CO (United States)]; Grandqvist, C.G. [ed.] [Uppsala Univ. (Sweden). Dept. of Technology]; PB: 379 p.; Proceedings/SPIE, Volume 2531
- Country of Publication:
- United States
- Language:
- English
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