Thermal expansion study on LnMgAl11O19 (Ln=La, Gd) by high temperature X-ray diffraction. Issue 6 (15th March 2022)

• Record Type: Journal Article
• Authors: Xu, Chunhui; Chang, Xiaohong; Huo, Keli; Luo, Lirong; Zhang, Xiaoshan; Nie, Dongxu; Hou, Shuen; Jin, Hongyun
• Is Part Of: Ceramics international. Volume 48:Issue 6(2022)
• Page Start: 8572
• Page End: 8578
• Publication Date: 2022-03-15
• Subjects: Thermal barrier coatings -- Lanthanide magnesium hexaaluminate -- High-temperature X-ray diffraction -- Lattice thermal expansion -- Macroscopic thermal expansion; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2021.12.067
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Thermal expansion performance is essential for lanthanide magnesium hexaaluminate (LnMgAl11 O19, Ln=La, Gd) top-coating as the thermal barrier coatings materials. In the present work, LnMgAl11 O19 (Ln= La and Gd) with magnetoplumbite structure was synthesized by the chemical co-precipitation method. The lattice thermal expansion behavior of both the samples was investigated using a high-temperature X-ray diffraction test combined with Reitveld refinement. The results showed that the thermal expansion of the a-axis was smaller than that of the c-axis, which was related to the anisotropic elongation of Ln-O bonds in the [LaO12 ] clusters. Meanwhile, the lattice expansion coefficient of the LaMgAl11 O19 was higher than that of GdMgAl11 O19 . This was confirmed by the result of the macroscopic thermal expansion which was measured using a high-temperature dilatometry. The underlying mechanism was discussed, which was due to the weaker bond energy of La–O than that of Gd–O.