Infrared Reflection of Ba(Mg _1/3 Ta _2/3 )O ₃ Ceramics

Abstract

The dielectric function of the ordered Ba(Mg 1/3 Ta 2/3 )O 3 ceramics was investigated by the infrared reflectance spectra taken over the 50–4000‐cm −1 range. The detailed crystal structure of the specimen was examined by the Rietveld method. The space group of trigonal D 3d 3 and the degree of long‐range order of 0.97 for Mg and Ta atomic arrangement were confirmed. The reflectance spectra were analyzed on the basis of the four‐parameter semiquantum model assuming 16 infrared active vibrational modes allowed for the related D 3d 3 structure. The lowest‐frequency optical mode was found at 60 cm −1 , which can be assumed to involve the motions of the heavy TaO 6 octahedra.