Lattice parameters of RE4Al2O9 (RE = Y, Sin, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) prepared at 1600–1800°C and those of RE4Ga2O9 (RE = La, Pr, Nd, Sm, Eu, and Gd) prepared at 1400–1600°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 (rRE). High‐temperature differential calorimetry and dilatometry revealed that both RE4Al2O, and RE4Ga2O, have reversible phase transitions with volume shrinkages of 0.5–0.7% on heating and thermal hystereses. The transition temperatures (7tr) decreased from 1300°C (Yb) to 1044°C (Sm) for RE4A12O9, except for Y4Al2O9 (Ttr= 1377°C), and from 1417°C (Gd) to 1271°C (La) for RE4Ga2O, with increasing ionic radius of the rare‐earth elements. These transition temperatures were plotted on a curve against the ionic radius ratio of Al3+ or Gd3+ and RE3+ (rA1Ga/rRE) except for Y4Al2O9.
|Number of pages||6|
|Journal||Journal of the American Ceramic Society|
|Publication status||Published - 1995 Sep|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry