Structure and Microwave Dielectric Behavior of A‐Site‐Doped Sr_(1−1.5x)Ce_xTiO₃ Ceramics System

Abstract

The ion valence state, phase composition, microstructure, and microwave dielectric properties of Sr(1−1.5x)CexTiO3 (x = 0.1–0.67, SCT) ceramics were systematically investigated. Sr(1−1.5x)CexTiO3 ceramics were produced with gradual structural evolution from a cubic to a tetragonal and turned to an orthorhombic structure in the range of 0.1 ≤ x ≤ 0.67. Above a critical Ce proportion (x = 0.4), microstructural changes and normal grain growth initially occurred. On the basis of chemical analysis results, the reduction of Ti4+ ions was hastened by tetravalent ions (Ce4+). By contrast, this reduction was inhibited by trivalent ions (Ce3+). The observed dielectric behavior was strongly influenced by phase composition, oxygen vacancies (VnormalO∙∙), and defect dipoles, namely, (Ti′−VO∙∙) and (VSr″−VO∙∙). Temperature stable ceramics sintered at 1350°C for 3 h in air yielded an intermediate value of dielectric constant (εr = 40), with the smallest reported value of temperature coefficient of resonant frequency (τf = +0.9 ppm/°C), and quality factor (Q × f = 5699 GHz) at x = 0.6.

Cauliflower-like CeO2–TiO2hybrid nanostructures with extreme photocatalytic and self-cleaning properties

“…Moreover, the presence of Ce 3+ may inhibit the reduction of Ti 4+ because of the favorable electron compensation. 24 As shown in Fig. 2d, we observed differences in binding energies of Ti-2p core level (Ti-2p3/2 and Ti-2p1/2 spin-orbit splitting) acquired for TiO2 and CeO2-TiO2 hybrid structures.…”

“…The relative high area ratio O2/O1, (0.38) in the CeO2-TiO2 O-1s spectrum in comparison to that of TiO2 (0.16) could point to an increase of oxygen vacancies. 24 Detailed deconvolution of O-1s core levels is shown in the supplementary information (Fig. S8) The photocatalytic activity of the prepared CeO2-TiO2 hybrid catalyst was first evaluated by degrading Methylene Blue (MB) under ultra-violet (UV) light irradiation (in comparison to bare TiO2) as shown in Fig.…”

High dielectric constant and high‐Q in microwave ceramics of SrTiO3 co‐doped with aluminum and niobium

“…As some ions tend to segregate at the grain boundaries, the growth of grain is restrained. 19 As a result, the grains tend to become small and uniform with the increment of doping content. As presented in Figure 2 (C) and (D), the average grain size decreases to~1.30 lm when x = 0.1 and becomes a little smaller at x = 0.15.…”

The latest process and challenges of microwave dielectric ceramics based on pseudo phase diagrams

“…(1-x)Mg(Ti 0.95 Sn 0.05 )O 3 -xBaTiO 3 compounds experienced a phase transition of tetragonal-structure BaTiO 3 , monoclinic-structure Ba 4 Ti 11 O 26 , and triclinic-structure Ba 2 Ti 9 O 20 [419]. Likewise, Sr (1-1.5x) Ce x TiO 3 (x = 0.1-0.67) ceramics changed from cubic, tetragonal, to orthorhombic, and the dielectric behaviors were dominated by oxygen vacancies and defect dipoles [420]. Tian et al [421,422] reported that (Co 0.5 W 0.5 ) 4+ and (Zn 0.5 W 0.5 ) 4+ occupying the Ti-site in BaTiO 3 would render the τ f value change from positive to negative.…”