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Crystal Structure and Infrared Reflection Spectra of SrLn 2 Al 2 O 7 (Ln = La, Nd, Sm) Microwave Dielectric Ceramics
Author(s) -
Yi Lei,
Liu Xiao Qiang,
Chen Xiang Ming
Publication year - 2014
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/ijac.12366
Subject(s) - materials science , dielectric , crystal structure , octahedron , crystal (programming language) , microwave , analytical chemistry (journal) , ceramic , phonon , reflection (computer programming) , far infrared , spectral line , infrared , crystallography , mineralogy , condensed matter physics , optics , physics , chemistry , optoelectronics , chromatography , quantum mechanics , astronomy , computer science , programming language , composite material
SrLn 2 Al 2 O 7 (Ln = La, Nd, Sm) ceramics belonging to Ruddlesden–Popper phase with n = 2 in space group I 4 /mmm have been prepared by a standard solid‐state reaction process. Their crystal structure refinement and infrared reflection spectra analysis have been carried out to investigate the correlations among the crystal structure, polar phonon modes, and microwave dielectric characteristics. Heavy deviations of cation–oxygen bonds in (Sr,Ln)O 12 , (Sr,Ln)O 9 , and AlO 6 polyhedra are observed, and the deviations significantly affect the microwave dielectric characteristics of the present ceramics. The polar phonon modes with lower frequencies due to translation vibration of Sr/La ions against the AlO 6 octahedron give the primary contribution to dielectric constant and intrinsic dielectric loss at microwave frequencies. The calculated Q × f value is significantly larger than the measured one, and this result is very obvious for SrLa 2 Al 2 O 7 ceramics where the calculated one (130,300 GH z) is about 2 times of the measured one (68,800 GH z).