Reduction of praseodymium and terbium higher oxides: chemical reactions similar to diffusionless phase transitions

Journal Article · Tue Dec 01 04:00:00 EST 1987 · J. Solid State Chem.; (United States)

DOI:https://doi.org/10.1016/0022-4596(87)90255-6· OSTI ID:5572475

Boulesteix, C; Eyring, L

Some solid state chemical reactions such as a change in the degree of oxidation can occur without a great displacement of the atomic positions of one kind of atom in a structure. When praseodymium and terbium oxides are reduced, the rare earth atom movement is less than the cations crystallographic distances in the fluorite-related structure. This means that the chemical transformation occurs without a great change in the framework of one kind of atom. The relative positions of these atoms are nevertheless slightly modified as in a diffusionless phase transition. In the Pr and Tb oxides the deformation changes both the volume and the shape of the structural unit. A displacement tensor can be defined for these chemical transformations. Interfaces between the two phases can be found as in ferroelastic or martensitic phase transitions by satisfying the condition of a strain-free interface. No general solution exists under these circumstances but approximate solutions exist for thin layers which give needle-like domains. The great number of glide defects in only one direction that occur in the iota phase of praseodymium thin layers obtained by reduction of the zeta phase can then be related to the chemical transformation itself. Similar results are obtained in bulk material but the transformation mechanism is not yet completely settled.

• Research Organization: Arizona State Univ., Tempe
• OSTI ID: 5572475
• Journal Information: J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 71:2; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
DATA
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
INFORMATION
MICROSCOPY
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
REDUCTION
SCATTERING
TERBIUM COMPOUNDS
TERBIUM OXIDES
X-RAY DIFFRACTION