Vibrational analysis of Ba5-xSrxNb4O15 microwave dielectric ceramic resonators

The Ba5-xSrxNb4O15 ceramics have been prepared and characterised using XRD, Raman, FTIR, and microwave dielectric property measurements. The measured dielectric properties show smooth variation with Sr content. The spectroscopic studies show that the symmetry of the NbO6 octahedra increases with increase in strontium content, maintaining the hexagonal structure. Hence, the possibility of a monoclinic structure for Sr5Nb4O15 seems to be inappropriate. The observed symmetric stretching bands of NbO, octahedra confirm the existence of corner connected octahedra in all the solid solution compounds. The behavior of the dielectric constant of (Ba5-xSrx)Nb4O15 system can be correlated to the variation of symmetric stretching vibrations of NbO6 octahedra. (C) 1997 Academic Press.