Long range B-site cation ordering and Briet–Wigner–Fano line shape of A_1g-like Raman mode in Nd_1−xSm_x(Mg_0.5Ti_0.5)O₃ microwave dielectric ceramics

Abstract

Nd_1−xSm_x(Mg_0.5Ti_0.5)O₃ (x = 0.0–1.0) samples were prepared by solid-state reaction method. Rietveld refinement of X-ray diffraction data was done using P2₁/n space group with monoclinic symmetry, which supports 1:1 B-site cation ordering. Long Range Ordering (LRO) parameter decreased up to x = 0.5 and then found to increase with further increase in Sm concentration. The A_1g-like mode in Raman spectra was observed to possess Briet–Wigner–Fano line shape. The variation in obtained line width of the A_1g-like mode supported LRO. Microwave dielectric characteristics such as dielectric constant (ε_r), quality factor (Q) and temperature coefficient of resonant frequency (τ_f) were measured in the range of 7–9 GHz. ε_r decreased from 26.5 to 24.9 and τ_f become less negative from −58 ppm/°C to −36 ppm/°C with increase in Sm concentration. Q × f decreased from 47,500 GHz (for x = 0) to 39,800 GHz (for x = 0.5) and then increased to 44,600 GHz (for x = 1).