Electron Spin Resonance Investigations and Compensation Mechanism of Europium-Doped Barium Titanate Ceramics

Authors:
  • DLDa-Yong Lu
    Da-Yong Lu
  • XSXiu-Yun Sun
    Xiu-Yun Sun
  • MTMasayuki Toda
    Masayuki Toda
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Abstract
The electron spin resonance (ESR) technique was employed to investigate the point defects and evidence of Eu2+ in Eu-doped barium titanate (EBT) ceramics sintered in air according to the formula (Ba1-x Eu x )Ti1-x/8O3. The charge equilibrium compensation mechanism was discussed on the basis of ESR with the aid of X-ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques. Eu is incorporated into Ba sites of BaTiO3 as Eu3+ up to x=0.02 and as mixed Eu2+/Eu3+ at x=0.03, which is evidenced by Eu3+-induced Ti-vacancy defects with g=2.004 and a broad Eu2+ signal with g=1.98, and a single-phase tetragonal perovskite structure can be retained. When x≥0.04, it is concluded that high density and low porosity in highly insulating and fine-grained EBT ceramics originate from the coexistence of mixed Eu2+/Eu3+; in particular, the increase in the proportion of Eu2+ in the perovskite phase increases ceramic density, but is accompanied by emergence of the Eu2Ti2O7 phase.

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