Phase transitions of the system Ag sub 2 HgI sub 4 -Cu sub 2 HgI sub 4 at normal and high pressure studied by differential scanning calorimetry

Journal Article · Thu Feb 08 04:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100366a019· OSTI ID:7031363

Friesel, M; Baranowski, B; Lunden, A ^[1]

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1. Chalmers Univ. of Technology, Goeteborg (Sweden)

Differential scanning calorimetry has been applied for studying the system Ag{sub 2}HgI{sub 4}-Cu{sub 2}HgI{sub 4} at both normal and high pressure. It is confirmed that there is a miscibility gap in the ordered phase and that the order-disorder phase transition has a eutectoid point at 307 K and 42.7 mol % Cu{sub 2}HgI{sub 4} at normal pressure, which is about 30 K higher than expected from a calculation for ideal eutectic behavior. The order-disorder transition is of first-order character over the whole composition range, confirming the interpretation by Suchow and ruling out the suggestion by Jaffray that it should be of second-order character in the middle part of the range. The transition enthalpy is equal to 7.3 {plus minus} 0.2 kJ/mol for the eutectoid composition. The phase diagram of the eutectoid composition was determined for pressures up to 0.72 GPa, and the temperature of the order-disorder transition increased from 307 to about 325 K, The correlation was not linear over the whole pressure range, but an average dT/dP slope of 25 K/GPa is in good agreement with the 24 K/GPa calculated by means of van Laar,s formula. The transition enthalpy (kJ/mol) decreased linearly with increasing pressure with d{Delta}H/dp = -4.0 kJ/(mol GPa). A calculation from simple additive rule gives instead d{Delta}H/dp = -1.5 kJ/(mol GPa).

• OSTI ID: 7031363
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:3; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400200* -- Inorganic
Organic
& Physical Chemistry
CALCULATION METHODS
COPPER
DATA ANALYSIS
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
HIGH PRESSURE
IODIDES
IODINE COMPOUNDS
MEASURING INSTRUMENTS
MEASURING METHODS
MERCURY COMPOUNDS
MERCURY HALIDES
MERCURY IODIDES
METALS
MICROSCOPY
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
PRESSURE EFFECTS
SCANNING LIGHT MICROSCOPY
SILVER
TRANSITION ELEMENTS