Spinel/oxide interfaces formed by internal solid-state reactions

1983 ◽  
Vol 41 ◽  
pp. 54-55
Author(s):  
K. M. Ostyn ◽  
H. Schmalzried ◽  
C. B. Carter
Keyword(s):  
Solid Solution ◽  
Solid State ◽  
Solid State Reaction ◽  
Elevated Temperatures ◽  
Solid State Reactions ◽  
Second Phase ◽  
Oxide Interfaces ◽  
Valence States ◽  
Internal Reaction ◽  
Kinetics Of

The usual method of forming the spinel AB2O4 by a solid-state reaction is to bring two oxides, AO and B2O3, into contact with one another at elevated temperatures, where diffusion is fast. The spinel then grows into both parent oxides; the kinetics of this solid-state reaction are well understood. Spinel can also be formed by exsoluting it as a second-phase in an oxide matrix. The two distinct internal reaction systems which have been used in this study are internal reduction and internal oxidation. Starting with an (Al-xBx)2O3 (x<1) solid solution, where one of the cations (B) can exist in at least two different valence states, it is possible to form spinel particles in an almost pure A2O3 matrix by internal reduction. Similarly, an (Al-xBX)O solid solution can be internally oxidized to form spinel in an almost pure AO matrix.

The wustite-spinel interface

1987 ◽  
Vol 45 ◽  
pp. 268-269
Author(s):  
S.R. Summerfelt ◽  
C.B. Carter
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Strain Energy ◽  
Matrix Material ◽  
Lattice Misfit ◽  
Solid State Reactions ◽  
Oxygen Sublattice ◽  
Large Particles ◽  
Small Lattice ◽  
Coherent Interfaces

The wustite-spinel interface can be viewed as a model interface because the wustite and spinel can share a common f.c.c. oxygen sublattice such that only the cations distribution changes on crossing the interface. In this study, the interface has been formed by a solid state reaction involving either external or internal oxidation. In systems with very small lattice misfit, very large particles (>lμm) with coherent interfaces have been observed. Previously, the wustite-spinel interface had been observed to facet on {111} planes for MgFe2C4 and along {100} planes for MgAl2C4 and MgCr2O4, the spinel then grows preferentially in the <001> direction. Reasons for these experimental observations have been discussed by Henriksen and Kingery by considering the strain energy. The point-defect chemistry of such solid state reactions has been examined by Schmalzried. Although MgO has been the principal matrix material examined, others such as NiO have also been studied.

Electric-Field Effects on Reactions Between Oxides

1997 ◽  
Vol 481 ◽  
Author(s):  
Matthew T. Johnson ◽  
Shelley R. Gilliss ◽  
C. Barry Carter
Keyword(s):  
Solid State ◽  
Electric Field ◽  
Elevated Temperatures ◽  
Ionic Current ◽  
Reaction Rates ◽  
Solid State Reactions ◽  
Interfacial Stability ◽  
Electric Field Effects ◽  
Thin Film Diffusion ◽  
Microscopy Techniques

ABSTRACTThin films of In2O3 and Fe2O3 have been deposited on (001) MgO using pulsed-laser deposition (PLD). These thin-film diffusion couples were then reacted in an applied electric field at elevated temperatures. In this type of solid-state reaction, both the reaction rate and the interfacial stability are affected by the transport properties of the reacting ions. The electric field provides a very large external driving force that influences the diffusion of the cations in the constitutive layers. This induced ionic current causes changes in the reaction rates, interfacial stability and distribution of the phases. Through the use of electron microscopy techniques the reaction kinetics and interface morphology have been investigated in these spinel-forming systems, to gain a better understanding of the influence of an electric field on solid-state reactions.

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