DIELECTRIC-PROPERTIES AND AN EPR STUDY OF CU-DOPED OR ZR-DOPED BATIO3CERAMICS

The EPR spectra of Cu- or Zr-doped BaTiO3 ceramics exhibited absorptio n signals with g(parallel to)=2380 and g(perpendicular to)=2063 which are assigned,to Ba1+(Ba2++e'-->Ba1+) ion reduced by an electron that w as produced from the oxygen vacancy (V-0-). The intensity of these sig nals decreased as the temperature increased indicating that Ba1+ was c hanged to Ba2+ as the temperature increased. These ceramics also showe d the EPR signal with g=1.997 around Te which arises from ionized Ba-v acancies, V-Ba'(V-Ba+e'-->V-Ba'). In the orthorhombic and tetragonal p hase region g=1.997 signal was not seen. The electrons generating from the oxidation of Ba1+ and ionized Ba-vacancies may contribute to a sp ace charge which is responsible for a dielectric relaxation of these s amples.