This title appears in the Scientific Report : 2019 

Crystal structure analysis and high‐temperature phase transitions of complex rare‐earth perovskite, La 2 (Al 1/2 MgTa 1/2 )O 6
Sohn, Yoo Jung (Corresponding author)
Mauer, Georg / Roth, Georg / Guillon, Olivier / Vaßen, Robert
JARA-ENERGY; JARA-ENERGY
Werkstoffsynthese und Herstellungsverfahren; IEK-1
Journal of the American Ceramic Society, 103 (2020) 2, S. 1404-1413
Westerville, Ohio Soc. 2020
10.1111/jace.16740
Journal Article
Methods and Concepts for Material Development
OpenAccess
OpenAccess
Please use the identifier: http://hdl.handle.net/2128/23682 in citations.
Please use the identifier: http://dx.doi.org/10.1111/jace.16740 in citations.
In situ high‐temperature powder X‐ray diffraction analysis (HT‐XRD) was carried out in the temperature range from 25°C‐1430°C to investigate the crystal structure of double perovskites, La2(Al1/2MgTa1/2)O6 (LAMT) and its phase transitions. This complex perovskite is a promising candidate for application in thermal barrier coating systems. Rietveld analysis shows a rock‐salt type ordering of the B‐site cations in the monoclinic space group symmetry, P21/n at room temperature. Upon heating, a structural phase transition occurs at ~855°C, and the crystal structure becomes rhombohedral with the space group symmetry urn:x-wiley:00027820:media:jace16740:jace16740-math-0001. On further heating, LAMT transforms to the ideal cubic phase at ~1390°C with the space group symmetry urn:x-wiley:00027820:media:jace16740:jace16740-math-0002. Both of the structural phase transitions are completely reversible, and were confirmed through complementary differential scanning calorimetry and thermogravimetry measurements. With increasing temperature, the degree of the octahedral tilting decreases and the variance of the different B–O bond lengths is reduced, until in the cubic phase, no tilting is present, and almost equal B–O bond lengths are obtained.