X-ray Diffraction, Dielectric, and Raman Spectroscopy Studies of SrTiO3-Based Microwave Ceramics

Abstract

xSrTiO3-(1 − x)Ca0.61Nd0.26TiO3 (SCNTx) and xSrTiO3-(1 − x)Na1/2La1/2TiO3 (SNLTx) ceramics were studied by x-ray diffraction and Raman spectroscopy in the composition range of 0.1 ≤ x ≤ 0.4. The x-ray patterns illustrated that the SCNTx (0.1 ≤ x ≤ 0.4) solid solutions had a single orthorhombic perovskite phase, while a single phase with pseudoorthorhombic structure was identified for the SNLTx (0.1 ≤ x ≤ 0.4) ceramics. In addition, the Lorentz fitting method was applied to separate the Raman spectra into several individual peaks. Meanwhile, the line shift and width of the main phonons are also discussed based on the Lorentz fitting method. Among these, some new peaks at about 470 cm−1/483 cm−1 and 442.31 cm−1/429.20 cm−1 appeared for the SCNTx and SNLTx samples with 0.3 ≤ x ≤ 0.4 due to A-site occupation by two or more types of cation with different electrovalence. Based on the resulting Q × f value and full-width at half-maximum of the A1g(O) stretch mode, it was found that propagation of microwave energy in the SCNTx samples showed stronger damping behavior; a smaller Q × f value was therefore expected with an increase in Sr content. Moreover, the τf value and tolerance factor (t) exhibited a proportional correlation because of increasing symmetry of the perovskite phase for the SNLTx (0.1 ≤ x ≤ 0.4) ceramics.