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Solid‐state synthesis of multicomponent equiatomic rare‐earth oxides
Author(s) -
Pianassola Matheus,
Loveday Madeline,
McMurray Jake W.,
Koschan Merry,
Melcher Charles L.,
Zhuravleva Mariya
Publication year - 2020
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.16971
Subject(s) - monoclinic crystal system , sintering , materials science , reducing atmosphere , crystallite , oxidizing agent , inert gas , atmosphere (unit) , ceramic , chemical engineering , oxidation state , phase (matter) , mineralogy , metallurgy , crystallography , crystal structure , metal , chemistry , composite material , thermodynamics , organic chemistry , physics , engineering
Phase formation in multicomponent rare‐earth oxides is determined by a combination of composition, sintering atmosphere, and cooling rate. Polycrystalline ceramics comprising various combinations of Ce, Gd, La, Nd, Pr, Sm, and Y oxides in equiatomic proportions were synthesized using solid‐state sintering. The effects of composition, sintering atmosphere, and cooling rate on phase formation were investigated. Single cubic or monoclinic structures were obtained with a slow cooling of 3.3°C/min, confirming that rare‐earth oxides follow a different structure stabilization process than transition metal high‐entropy oxides. In an oxidizing atmosphere, both Ce and Pr induce a cubic structure, while only Ce plays that role in an inert or reducing atmosphere. Samples without Ce or Pr develop a single monoclinic structure. The structures formed at initial synthesis may be converted to a different one, when the ceramics are annealed in an additional atmosphere. Phase evolution of a five‐cation composition was also studied as a function of sintering temperature. The binary oxides used as raw materials completely dissolve into a single cubic structure at 1450°C in air.

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