A remarkable CER(colossal electroresistance) effect was observed in a series of polycrystalline Nd0.67Sr0.33MnO3 samples synthe-sized by high energy ball milling successive heat treatment.The CER ratio increased with increasing heating time and reached 3580% at a low temperature for the Nd0.67Sr0.33MnO3 ceramic annealed up to 13 h as measuring current was enhanced from 5 to 500 μA.The result showed that the CER effect was strongly dependent on the sample's microstructure,especially on the foreign phases which were gradually developed within grain boundaries when annealing time was more than 3 h.
Oxygen deficient Nd0.67Sr0.33MnO3-δ ceramic samples were prepared using conventional ceramic technology. A colossal electroresistance (CER) effect was found in Nd0.67Sr0.33MnO3-δ series. The electrical transport is magnetically coupled and spin-dependent over grain or phase boundaries. Electrical-field-induced changes of the spin array orientations inside of and between the magnetic domains by grain or phase boundaries have to be concluded for the strong electroresistive effect in Nd0.67Sr0.33MnO3-δ series.
Strontium doped perovskite-type Nd0.7Sr0.3MnO3 ceramics were synthesized completely by high-energy ball milling raw oxides of Nd2O3, SrCO3 and MnO2. The optimal ball milling time and mass ratio of milling balls to raw materials are 4 h and 10:1, respectively. The grain size of as-milled Nd0.7Sr0.3MnO3 ceramics ranges from 51 to 93 nm, and the fine particles contain two phases of crystalline phase and amorphous phase. For the Nd0.7Sr0.3MnO3 synthesized by ball milling and sequent heat treatment, a remarkable colossal electroresistance (CER) effect is observed and the CER ratio reaches 900% at Curie temperature TC when the load voltage increases from 0.1 to 0.8 V.
