Self-compensation characteristics of Eu ions in BaTiO3

In order to clarify whether the mixed valence of Eu2+/Eu3+ exists in a self-compensation mode in Eu-doped BaTiO3, the site occupation and valence state of Eu ions in barium titanate were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), electron spin resonance (ESR), Raman spectroscopy (RS), and dielectric measurements. The results indicate that Eu ions may enter both Ba- and Ti-sites as Eu3+, forming a self-compensation mode with the amphoteric behavior. Self-compensation characteristics of Eu ions in BaTiO3 are reflected by an expansion in unit cell volume, evolution of the 830 cm− 1 Raman band, strong diffusion of the dielectric peak, disappearance of the Eu2+ ESR broad signal, and a g = 2.004 signal independent of temperature.

► Eu ions in BaTiO3 may behave as both donor (A-site) and acceptor (B-site).
► All Eu ions are trivalent when a self-compensating mode is formed.
► The self-compensating mode is evidenced by an expansion in unit cell volume.
► A broadened, lowered and red-shifted Raman band appears at 830 cm− 1.
► The strong diffusion of dielectric peak occurs for the self-compensating mode.