Cubic-to-tetragonal displacive transformation in Gd[sub 2]O[sub 3]-Bi[sub 2]O[sub 3] ceramics

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1993.tb03974.x· OSTI ID:5629615

Su, P; Virkir, A V ^[1]; Hubbard, C R; Cavin, O B; Porter, W D ^[2]

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1. University of Utah, Salt Lake City, (United States)
2. Oak Ridge National Lab., TN (United States)

Gd[sub 2]O[sub 3]-doped Bi[sub 2]O[sub 3] polycrystalline ceramics containing between 2 and 7 mol% Gd[sub 2]O[sub 3] were fabricated by pressureless sintering powder compacts. The as-sintered samples were tetragonal at room temperature. High-temperature X-ray diffraction (XRD) traces showed that the samples were cubic at elevated temperatures and transformed into the tetragonal polymorph during cooling. On the basis of conductivity measurements as a function of temperature and differential scanning calorimetry (DSC), the cubic [r arrow] tetragonal as well as tetragonal [r arrow] cubic transition temperatures were determined as a function of Gd[sub 2]O[sub 3] concentration. The cubic [r arrow] tetragonal transformation appears to be a displacive transformation. It was observed that additions of ZrO[sub 2] as a dopant, which is known to suppress cation interdiffusion in rare-earth oxide-Bi[sub 2]O[sub 3] systems, did not suppress the transition, consistent with it being a displacive transition. Annealing of samples at temperatures [le] 660 C for several hundred hours led to decomposition into a mixture of monoclinic and rhombohedral phases. This shows that the tetragonal polymorph is a metastable phase.

• OSTI ID: 5629615
• Journal Information: Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 76:10; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
BISMUTH COMPOUNDS
BISMUTH OXIDES
CERAMICS
CHALCOGENIDES
COHERENT SCATTERING
DIFFRACTION
GADOLINIUM COMPOUNDS
GADOLINIUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
RARE EARTH COMPOUNDS
SCATTERING
X-RAY DIFFRACTION