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Properties of the new electronic device material La G dO 3
Author(s) -
Pavunny Shojan P.,
Kumar Ashok,
Misra Pankaj,
Scott James F.,
Katiyar Ram S.
Publication year - 2014
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201349257
Subject(s) - raman spectroscopy , monoclinic crystal system , tetragonal crystal system , rietveld refinement , crystallography , crystal structure , materials science , molecular vibration , powder diffraction , analytical chemistry (journal) , chemistry , physics , optics , chromatography
The room temperature crystal structure of potential high‐ k dielectric LaGdO 3 has been analyzed by X‐ray diffraction techniques and its structural evolution with temperature has been probed by Raman spectroscopy. Rietveld refinement of the ambient XRD data established the perfectly layered B‐type monoclinic crystal structure with a = 14.43 Å, b = 3.68 Å, c = 8.99 Å, and β = 100.57° which is further validated by the 21 (14 A g and 7 B g ) Raman‐active vibrational modes with centro‐symmetric space groupC 2 h 3or C 2/ m . Atomic positions, coordination numbers, inter‐ionic lengths, etc. were derived using Rietveld analysis. All prominent Bragg peaks were successfully indexed. Temperature dependent Raman spectra of LaGdO 3 from 80 to 1400 K were analyzed using the damped harmonic oscillator model. The softening and hardening of vibrational modes are reported. Above 900 K, disappearance of all high frequency modes (>600 cm −1 ) and merger of several mid frequency modes (between 200 and 500 cm −1 ) into two distinct modes was observed, a direct evidence of a possible structural phase transition from monoclinic to tetragonal/pseudocubic.