Defect chemistry of a high-k ‘Y5V’ (Ba0.95Eu0.05)TiO3 ceramic

The influence of the sintering temperature (Ts) on the structure, dielectric and valence-state properties of (Ba1−xEux)TiO3 (x=0.05) ceramics was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), Raman spectroscopy, and dielectric temperature measurements. An increase in Ts can increase the solubility limit of Eu in BaTiO3. When the Ts was increased to 1450 °C, a high-k ‘Y5V’ (ε′RT=8500) ceramic (C-BE5T) with a single-phase cubic structure was obtained. The dielectric peak shifted rapidly toward lower temperatures with increasing Ts at a rate of −0.46 °C/K. A symmetric (200) XRD peak, exaggerated grain growth (5.6 μm), a mixed valence of Eu2+/Eu3+, an asymmetric main Raman band at 2494 cm−1 and a weak sharp band at 1516 cm−1 in the high-wavenumber region are characteristics of cubic symmetry of C-BE5T. The formation of a solid solution of C-BE5T and defect chemistry are discussed.