Lanthanum‐Magnesium and Lanthanum‐Manganese Donor‐Acceptor‐Codoped Semiconducting Barium Titanate

Abstract

BaTiO3 powder doped with La donor and codoped with Mn or Mg acceptor was sintered at 1350°C/1 h in air. For Ladoped BaTiO3, the room‐temperature resistivity decreased to a minimum at [La3+] ∼ 0.15 mol%. For La‐Mn‐codoped BaTiO3, the minimum resistivity occurred at [La3+] ‐ 2[Mn2+] ∼ 0.15 mol%. When the ceramic was changed to a fine‐grained insulator by high donor doping ([La3+] >0.15 mol%), its semiconductivity was restored, and the relatively homogeneous, coarse‐grained microstructure recurred by codoping with either Mg or Mn acceptor, with the transition at [La3+] ‐ 2[Mg2+] = 0.15 mol% or [La3+] ‐ 2[Mn2+] = 0.15 mol%. The analogy of a compensation effect between La‐Mn‐ and La‐Mg‐codoped BaTiO3 suggested that Mn acceptor added to BaTiO3 exists as Mn2+ ion in the bulk grain region; its influence on the positive temperature coefficient of resistivity behavior is then discussed.