Properties of the new electronic device material LaGdO3

The room temperature crystal structure of potential high-k dielectric LaGdO3 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 angstrom, b=3.68 angstrom, c=8.99 angstrom, and =100.57 degrees which is further validated by the 21 (14A(g) and 7B(g)) Raman-active vibrational modes with centro-symmetric space group C2h3 or C2/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 LaGdO3 from 80 to 1400K were analyzed using the damped harmonic oscillator model. The softening and hardening of vibrational modes are reported. Above 900K, disappearance of all high frequency modes (>600cm(-1)) and merger of several mid frequency modes (between 200 and 500cm(-1)) into two distinct modes was observed, a direct evidence of a possible structural phase transition from monoclinic to tetragonal/pseudocubic