Structural phase transition and microwave dielectric properties of Ca1−x Sr x TiO3 (x = 0.1–0.9) ceramics

Abstract

Single phase Ca 1-x Sr x TiO 3 (x = 0.1, 0.25, 0.5, 0.75 and 0.9) bulk ceramics samples were prepared through a mixed oxide solid state sintering route. All the samples were characterized using synchrotron X-ray diffraction, Raman spectroscopy, scanning electron microscopy and vector network analyzer. Structural analysis revealed structural phase transition from orthorhombic (Pbnm) to tetragonal (I4/mcm) at x [ 0.5, consistent with the present Raman spectroscopy results. There was no evidence of orthorhombic Bmmb symmetry in the range x = 0.1-0.9. Relative permittivity varied from 148 to 241, quality factor from 7,427 to 1,487 GHz and temperature coefficient of resonance frequency from ?320 to ?479 ppm/°C with an increase in x from 0.1 to 0.9.

Structure and microwave dielectric properties of Ca0.66La0.387Ti0.88O3 ceramics

“…The room temperature Raman spectrum of Ca 0.66 La 0.387 Ti 0.88 O 3 is shown in Fig. 2, showing seven Raman bands, in agreement with Saleem et al [13]. The mode near 122 cm -1 may be the lattice mode.…”

Sintering behavior and microwave dielectric properties of CaTi1-x(Nb1/2Al1/2)xO3

“…A total of 13 Raman modes were detected (Table 1) which are in agreement with previous studies [12,15,16]. The band near 637 cm -1 for the sample with x=0.1 can be allocated to the Ti-O symmetric stretching mode [17], which disappeared as the Ti4 + is replaced by the dopant Al 3+ and Nb 5+ . The intensity of the band near ~ 804 cm -1 increased with increasing concentration which is assigned to the rotation of BO6 octahedra [12].…”

Structural investigation and improvement of microwave dielectric properties in Ca(HfxTi1-x)O3 ceramics

“…CaTiO 3 was reported to have a high relative permittivity of ε r = 160, quality factor Qxf = 7000 GHz and is accompanied by a large positive temperature coefficient at resonant frequency τ f =850 ppm °C−1 [14,15]. However another study, ε r = 241, quality factor Qxf = 1487 GHz and temperature coefficient at resonant frequency τ f =+430 ppm °C−1 was reported for Ca 1-x Sr x TiO 3 [16].…”