Structure, microwave dielectric and optical properties of Ln(2/3)Gd(1/3)TiNbO(6) (Ln=Ce, Pr, Nd and Sm) ceramics

Abstract

The Ln(2/3)Gd(1/3)TiNbO(6) ceramic compositions are prepared through the solid state ceramic route. The compositions are calcined at 1250 A degrees C and sintered in the range 1350-1435 A degrees C. Structural analysis of the materials is done using X-ray diffraction analysis and vibrational spectroscopy. Surface morphology is examined by Scanning Electron Microscopy. Microwave dielectric properties such as dielectric constant (epsilon(r)), quality factor (Q) and temperature coefficient of resonant frequency (T-f) are measured using cavity resonator method. The compositions have epsilon(r) in between 46 and 41.8 and T-f in between +52 and +25 ppm/A degrees C. By the substitution of Gd, the T-f is reduced considerably with a slight decrease in dielectric constant. Cerium based composition had additional reflections other than that of aeschynite structure. For Pr, Nd and Sm based systems, solid solutions were formed. UV visible spectrum of the representative composition is recorded and the band gap energy is estimated. Photoluminescence spectra of the samples are recorded and the transitions causing emissions are identified. The materials are suitable for microwave and optoelectronic applications.