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Thermodynamic properties of PrRhO 3 and phase diagrams of the system Pr–Rh–O
Author(s) -
Jacob Kallarackel T.,
Muraleedharan Srilekshmi
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16606
Subject(s) - phase diagram , thermodynamics , gibbs free energy , intermetallic , enthalpy , standard enthalpy of formation , chemistry , isothermal process , materials science , phase (matter) , physics , organic chemistry , alloy
A solid‐state electrochemical cell with yttria‐stabilized zirconia (YSZ) as the electrolyte is used to measure accurately thermodynamic properties of PrRhO 3 in the range of temperature from 875 to 1325 K. The standard Gibbs energy of formation of PrRhO 3 with orthorhombically distorted perovskite structure from its binary oxides β ‐Rh 2 O 3 and hexagonal Pr 2 O 3 is given by, Δ G f oxo± 50 / Jmol - 1= - 67813 + 5.299 T / K. Invoking the Newmann‐Kopp rule, the standard enthalpy of formation from elements and standard entropy of PrRhO 3 at 298.15 K are evaluated: Δ H f o = - 1175.53 ± 3.26kJmol - 1andS o = 108.89 ± 0.1 . 3J mol - 1K - 1. Phase relations in the system Pr–Rh–O at 1200 K are computed from thermodynamic data. Calorimetric data on enthalpy of formation of two intermetallic compounds are combined with the semi‐empirical model of Miedema and phase diagram to estimate Gibbs energy of formation for the intermetallics and liquid alloys. An isothermal section of ternary phase diagram, an oxygen potential‐composition diagram in 2‐D and a 3‐D chemical potential diagram for the system Pr–Rh–O at 1200 K are presented. In addition, temperature‐composition diagrams at different oxygen pressures are developed. The diagrams provide a road map for design and optimization of processing routes for catalysts based on Rh.