M.K. Suresh

Spectroscopic Investigations on Ln(Zr1/3Ti2/3)TaO6 (Ln = Ce, Pr, Nd and Eu) Ceramics

In the present work, the authors have performed vibrational spectroscopic study of Ln(Zr1/3Ti2/3)TaO6 (Ln = Ce, Pr, Nd and Eu) ceramics by analyzing their Raman spectra. An attempt is made to correlate the structure and microwave dielectric properties of the samples with their vibrational spectroscopic characteristics. The Raman spectra are analyzed mainly on the basis of TaO6 octahedra. Zr substitution in LnTiTaO6 has not changed the prominent phase, however, the movement towards euxenite structure with increase in atomic number of the lanthanide has become faster. The broadening and splitting of lines observed in Nd and Eu based compounds indicate the distortion of octahedra. The negative value of τf of Eu based compounds indicates the presence of euxenite phase in addition to the prominent aeschynite phase. This is confirmed by the maximum distortion of the octahedra as indicated by the lower wavenumber, broadening and splitting of the characteristic Raman lines. The Raman shift of υ2(Eg) mode showed a...

Structural, spectroscopic and dielectric investigations on Ba{sub 8}Zn(Nb{sub 6-x}Sb{sub x})O{sub 24} microwave ceramics

Ba{sub 8}Zn(Nb{sub 6-x}Sb{sub x})O{sub 24} (x = 0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8 and 2.4) ceramics were prepared through the conventional solid-state route. The materials were calcined at 1250 {sup o}C and sintered in the range 1400-1425 {sup o}C. The structure of the system was analyzed by X-ray diffraction, Fourier transform infrared and Raman spectroscopic methods. The theoretical and experimental densities were calculated. The microstructure of the sintered pellets was analyzed using scanning electron microscopy. The low frequency dielectric properties were studied in the frequency range 50 Hz-2 MHz. The dielectric constant ({epsilon}{sub r}), temperature coefficient of resonant frequency ({tau}{sub f}) and the unloaded quality factor (Q{sub u}) are measured in the microwave frequency region using cavity resonator method. The {tau}{sub f} values of the samples reduced considerably with the increase in Sb concentration. The materials have intense emission lines in the visible region. The compositions have good microwave dielectric properties and photoluminescence and hence are suitable for dielectric resonator and ceramic laser applications.