Papers by Keyword: Defect Complexes

Abstract: Structure and dielectric properties of 5 % Ce and Ca co-doped BaTiO₃ ceramics were investigated. The site occupations and valence states were studied using XRD, Raman spectroscopy, SEM, EPR and dielectric measurements. The Ba/Ti ratio has dramatic effects on ceramic structure and properties. Two single-phase ceramics with Ba/Ti = 1 and 0.937 have tetragonal and cubic structure, showing diffuse phase transition and first-order phase transition behaviors, respectively. The former exhibit the site occupations of mixed Ca²⁺/Ce³⁺ at Ba sites and Ca²⁺/Ce⁴⁺ at Ti sites. Ce ions have priority over Ca²⁺ ions in entering Ti sites as Ce⁴⁺ when co-doping in BaTiO₃, which will impede Ca²⁺ ions to be incorporated completely into Ti sites.

Abstract: In order to investigate the evidence for the formation of Sr²⁺-Zr⁴⁺ defect complexes in high-k Sr and Zr co-doped BaTiO₃ ceramics, BaTiO₃, (Ba_0.85Sr_0.15)TiO₃, Ba (Ti_0.8Zr_0.2)O₃, and (Ba_0.85Sr_0.15)(Ti_0.8Zr_0.2)O₃ (BS15TZ20) ceramics were prepared using a mixed oxide method. The Y5V-type BS15TZ20 shows a high-k diffuse phase transition behavior (ε ́_m = 8000) and its Curie peak occurs near room temperature. The evolution in crystal structure and in dielectric property for the four samples gives four evidences for the formation of Sr²⁺-Zr⁴⁺ defect complexes in BS15TZ20. The splitting of the 720 cm^-1 Raman band does not relate to Sr²⁺-Zr⁴⁺ defect complexes, but to a multiphonon (A₁ (TO₂) + A₁ (TO₃)).

Abstract: The defects at the interface and in the oxide have been considered as the sources of mobility degradation at the SiC/SiO₂ interface as in the case of Si/SiO₂ system. By examining available experimental and theoretical results and performing new calculations, we show that thermal oxidation creates immobile carbon di-interstitial defects inside the semiconductor substrate, which are a major cause of the poor mobility in SiC/SiO₂ structures.