Crystal structure, Raman spectroscopy and microwave dielectric properties of xBa<inf>3</inf>MgNb<inf>2</inf>O<inf>9</inf>–(1-x)Ba<inf>2</inf>InNbO<inf>6</inf> [x = 0.4, 0.6, 0.8]

The dependence of the microwave dielectric properties of xBa3MgNb2O9–(1-x)Ba2InNbO6 [x = 0.4, 0.6, 0.8] on the structural parameters is investigated. The solid-state reaction technique is applied to synthesize these materials and the structural parameters are obtained from the Rietveld refinement of the X-ray diffraction (XRD) data of the samples. The Rietveld refinement confirms the tetragonal crystal structure of all the samples with space group P4/mnc (D4h6). It has been observed that the Raman shift of the stretching mode ν1 (BO6) and the ionic polarizability of the cations strongly influenced the dielectric constant (εr) whereas the value of the quality factor Qf depends upon the width of ν1 (BO6) mode. It is observed that the temperature coefficient of resonant frequency (τf) increases with the increase of the octahedral-distortion in the crystal structure. The factors affecting the microwave dielectric properties are discussed based on the vibrational and structural data.