Metastable Crystal Structure of Strontium- and Magnesium-Substituted LaGaO3 |
| |
Authors: | Michael Rozumek Peter Majewski Fritz Aldinger |
| |
Affiliation: | Pulvermetallurgisches Laboratorium, Max-Planck-Institut für Metallforschung, 70569 Stuttgart, Germany |
| |
Abstract: | The metastable crystal structure of strontium- and magnesium-substituted LaGaO3 (LSGM) was studied at room and intermediate temperatures using powder X-ray diffractometry and Rietveld refinement analysis. With increased strontium and magnesium content, phase transitions were found to occur from orthorhombic (space group Pbnm ) to rhombohedral (space group R [Threemacr] c ) at the composition La0.825Sr0.175Ga0.825Mg0.175O2.825 and, eventually, to cubic (space group Pm [Threemacr] m ) at the composition La0.8Sr0.2Ga0.8Mg0.2O2.8. At 500°C in air and at constant strontium and magnesium content, a phase transformation from orthorhombic (space group Pbnm ) to cubic (space group Pm [Threemacr] m ) was observed. For the orthorhombic modification, thermal expansion coefficients were determined to be α a ,ortho = 10.81 × 10−6 K−1, α b ,ortho = 9.77 × 10−6 K−1, and α c ,ortho = 9.83 × 10−6 K−1 (25°–400°C), and for the cubic modification to be αcubic= 13.67 × 10−6 K−1 (500°–1000°C). |
| |
Keywords: | solid oxide fuel cell transitions gallium/gallium compounds crystals/crystallization |
|
|