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

Abstract

BaTiO 3 powder doped with La donor and codoped with Mn or Mg acceptor was sintered at 1350°C/1 h in air. For Ladoped BaTiO 3 , the room‐temperature resistivity decreased to a minimum at [La 3+ ] ∼ 0.15 mol%. For La‐Mn‐codoped BaTiO 3 , the minimum resistivity occurred at [La 3+ ] ‐ 2[Mn 2+ ] ∼ 0.15 mol%. When the ceramic was changed to a fine‐grained insulator by high donor doping ([La 3+ ] >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 [La 3+ ] ‐ 2[Mg 2+ ] = 0.15 mol% or [La 3+ ] ‐ 2[Mn 2+ ] = 0.15 mol%. The analogy of a compensation effect between La‐Mn‐ and La‐Mg‐codoped BaTiO 3 suggested that Mn acceptor added to BaTiO 3 exists as Mn 2+ ion in the bulk grain region; its influence on the positive temperature coefficient of resistivity behavior is then discussed.