Crystal structure, Raman spectroscopy, far-infrared, and microwave dielectric properties of (1-x)La(MgSn)0.5O3-xNd(MgSn)0.5O3 system

The complex perovskite system (1-x)La(MgSn)(0.5)O-3-xNd(MgSn)(0.5)O-3 with the composition (x=0-1) was prepared by the solid state reaction method. Structural and spectroscopic studies were carried out to understand the variation of dielectric properties with x. Rietveld refinement was carried out with the initial model obtained by using the structure prediction and diagnostic software. The symmetry of the compositions was determined to be monoclinic with space group P2(1)/n, which corresponds to the a(-)a(-)c(+) tilting system, and the long-range order parameter was found to decrease with an increase in neodymium concentration. Raman spectra were analyzed by fitting the A(1g)-like mode to a Lorentzian peak shape. Intrinsic dielectric parameters were estimated by fitting infrared reflectance spectra with the four-parameter semiquantum model. Transverse optic phonon mode strengths and average phonon damping were calculated. The origin of increase in the intrinsic loss with the composition variation is discussed. Microwave measurements were carried out in the frequency range of 9-11 GHz. The dielectric constant decreases and the temperature coefficient of resonant frequency becomes less negative with the increase in neodymium concentration. (c) 2008 American Institute of Physics.