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Oxygen Nonstoichiometry and Thermodynamic Quantities of La 2 Ni 0.95 Al 0.05 O 4.025 + δ
Author(s) -
Jeon SangYun,
Singh Bhupendra,
Yoo YoungSung,
Hwang JinHa,
Song SunJu
Publication year - 2014
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.12795
Subject(s) - oxygen , chemistry , analytical chemistry (journal) , mineral redox buffer , atmospheric temperature range , partial pressure , mineralogy , thermodynamics , physics , chromatography , organic chemistry
The oxygen nonstoichiometry of La 2 Ni 0.95 Al 0.05 O 4.025 + δ ( LNAO ) is measured as a function of oxygen partial pressure ( p O 2 ) and temperature by coulometric titration method and thermogravimetric analysis ( TGA ) in 800°C–1000°C temperature range and 10 −16 ‐1 atm p O 2 range. The partial molar quantities for mixing of oxygen were calculated and results were compared with the literature results on La 2 NiO 4 + δ ( LNO ). The variation in activity coefficient of holes versus oxygen nonstoichiometry illustrated an early positive deviation of the activity coefficient of holes from unity, leading to γ h ∙ ≈ 7 at δ ≈ 0.08, which was lower than the literature value of γ h ∙ ≈ 14 for La 2 NiO 4 + δ at δ ≈ 0.08, indicating lesser deviation of LNAO from ideal solution behavior. The effective mass of holes ( m h ∗ ) was 1.02–1.21 times the rest mass ( m o ), which indicated the band‐like conduction and allowed the effect of the small degree of polaron hopping to be ignored. The comparison of oxygen nonstoichiometry and partial molar quantities showed that incorporation of interstitial oxygen is less favorable in LNAO in comparison to LNO.