Phase transition of rare-earth aluminates (RE{sub 4}Al{sub 2}O{sub 9}) and rare-earth gallates (RE{sub 4}Ga{sub 2}O{sub 9})

Journal Article · Fri Sep 01 04:00:00 EDT 1995 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1995.tb08673.x· OSTI ID:116093

Yamane, Hisanori; Ogawara, Kazuhiro; Omori, Mamoru; Hirai, Toshio ^[1]

---

1. Tohoku Univ., Sendai (Japan). Inst. for Materials Research

Lattice parameters of RE{sub 4}Al{sub 2}O{sub 9} (RE = Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) prepared at 1,600--1,800 C and those of RE{sub 4}Ga{sub 2}O{sub 9} (RE = La, Pr, ND, Sm, Eu, and Gd) prepared at 1,400--1,600 C were refined by Rietveld analysis for the X-ray powder diffraction patterns. The parameters increased linearly with the ionic radius of the trivalent rare-earth elements (r{sub RE}). High-temperature differential calorimetry and dilatometry revealed that both RE{sub 4}Al{sub 2}O{sub 9} and RE{sub 4}Ga{sub 2}O{sub 9} have reversible phase transitions with volume shrinkages of 0.5--0.7% on heating and thermal hystereses. The transition temperatures (T{sub tr}) decreased from 1,300 C (Yb) to 1,044 C (Sm) for RE{sub 4}Al{sub 2}O{sub 9}, except for Y{sub 4}Al{sub 2}O{sub 9} (T{sub tr} = 1,377 C), and from 1,417 C (Gd) to 1,271 C (La) for RE{sub 4}Ga{sub 2}O{sub 9} with increasing ionic radius of the rare-earth elements. These transitions temperature were plotted on a curve against the ionic radius ratio of Al{sup 3+} or Gd{sup 3+} and RE{sup 3+} (r{sub Al,Ga}/r{sub RE}) except for Y{sub 4}Al{sub 2}O{sub 9}.

• Sponsoring Organization: USDOE
• OSTI ID: 116093
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 9 Vol. 78; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CALORIMETRY
CRYSTAL-PHASE TRANSFORMATIONS
DILATOMETRY
GALLIUM OXIDES
HYSTERESIS
LATTICE PARAMETERS
POWDERS
RARE EARTHS
SAMPLE PREPARATION
THERMAL EXPANSION
TRANSITION TEMPERATURE
X-RAY DIFFRACTION