Infrared reflection and Raman spectra have been measured f o r two complex perovskite ceramic materials, Ba-Two-mode behavior was observed for both of the compounds in the inner vibrations of the B0,-type octahedrons, where B indicates M n , Ta, and Ni ions. This behavior indicates that the local symmetry about M n , N i , and Ta ions is octahedral (OJ, although the superlattice structure of the compounds ( D 3 d ) is observed by XRD (Mn1/3Ta2/3)0.3 and Ba(Ni1,3Ta2/3)03~ 15 20 25 28 (CuKa)Fig. 1. XRD patterns for (A) Ba(Mn,,,-Tau3)03 and (B) Ba(Ni,,,Ta,,)O, in ceramic state. Cu-target X-rays were used. Diffraction peak indicated by (*) shows the formation of a hexagonal superstnrclure in D,, symmetry.analysis. [Key words: dielectrics, barium, nickel, tantalum, manganese.] R E C E N T investigations have demonstrated that some of the complex perovskite materials show extremely low dielectric losses at microwave frequencies, which can be a lied as microwave dielectric resonators!' Tamura et al. measured the XRD pattern of Ba(Zn113Ta2,3)03r which is abbreviated as BZT, and showed that the compound has superlattice structure of D3d symmetry as reported by Galasso and In the present investigation, we measured the far-infrared (IR) reflection and Raman spectra of Ba(Mn,,,Ta,,,)O, and Ba(Ni l,3Ta213)03, which are abbreviated as BMT and BNT, respectively, and discussed the vibration modes of the spectra.Samples were made from the starting materials of reagent-grade BaC03, MnCO,, NiO, and Ta205. They were mixed in stoichiometric ratios to form BMT and BNT and ball-milled for 24 h in pure water. After the samples were dried, they were heated at 1100°C for 4 h, cooled to room temperature, and ground in pure water for A 0 B' B" Fig. 2. Illustration of the hexagonal superstructure for the compound A(B I,,Bg3)03 after Galasso and Pyle4 for Ba(Znl,,Ta2,3)0,. 158 48 h. After they were again dried, they were pressed at 1 X lo8 Pa into disks 14 mm in diameter and 2 mm thick and heated at =1600°C for 2 h in air. The heating rate was =270"C/h. Finally they were cooled to room temperature within 24 h. Sample faces were polished to a mirror state. Figures ](A) and (B), show the XRD patterns of BMT and BNT, respectively. The refraction peaks, showing the formation of the D,, hexagonal superstructure, are indicated. The structure is illustrated in Fig. 2 after the report of Galasso and Pyle4 for BZT, where Zn and Ta ions occupy ordered configuration.Far-IR reflection spectra were measured at room temperature. According to the Kramers-Kronig analysis, the real and imaginary parts of the complex dielectric constants were calculated and are shown in Fig. 3. For comparison, the corresponding result for BaZrO, reported by Perry and McCarthy5 is shown. The frequencies for the peaks of the imaginary part ( E " ) correspond to those for the lattice vibrations of the transverse-optic (TO) mode. The en peaks of BaZrO, are located on the frequencies around 115, 210, and 505 cm-'. Since the crystal of BaZrO, belongs to the cubic symmetry (Ol...
