Dielectric and nonlinear electrical behaviors observed in Mn-doped Ca Cu3 Ti4 O12 ceramic

  • Cai J
  • Lin Y
  • Cheng B
 et al. 
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We present a remarkable effect of Mn doping on the dielectric and nonlinear electric properties of CaCu 3 Ti 4 O 12 ceramics. The results indicate that only 2.5 at. % Mn doping can suppress the dielectric permitivity in CaCu 3 Ti 4 O 12 by up to two orders of magnitude ͑from 10 4 to 10 2 ͒, and the nonlinear varistor characteristics disappear completely, which should be mainly ascribed to the decrease of potential barrier height at the grain boundary and charge compensation for the conduction electrons caused by the Mn doping. CaCu 3 Ti 4 O 12 ͑CCTO͒, as a complex cubic perovskite-like oxide, has attracted many attentions due to its unusual dielectric response of around 10 4 at room temperature and weak temperature dependence between 100 and 400 K. 1–3 Such special physical features and Ba/ Pb-free make it a promising material for the electronic devices. However, high dielectric loss of CCTO ceramic restricts its further applica-tion. Recently, CCTO/ CaTiO 3 composite, 4 TiO 2 -riched CCTO, 5 and La substitution on Cu sites in CCTO ͑Ref. 6͒ have been reported to be effective to reduce the dielectric loss and still remain high dielectric constant, which make it more reasonable for microelectronic application. As for the origin of the high dielectric properties, some researchers proposed that the high dielectric behavior should be attributed to local dipole moments associated with off-center displacement of Ti ions. 7 Moreover, Prakash and Varma 8 observed a ferroelectriclike hysteresis loop and py-roelectric behavior, which indicate that CCTO is a ferroelec-triclike material. On the other hand, extrinsic effects, such as the interfacial polarization effect, 9 the internal boundary layer capacitance ͑IBLC͒ effect, and the grain boundary effect 3,10–14 have also been proposed to understand the origin of the giant dielectric constant. Besides the giant dielectric properties, the non-Ohmic response 5,15–17 of CCTO has also been investigated by some researchers. Chung et al. 15 dis-covered that the bulk CCTO ceramics showed nonlinear current-voltage characteristics and the nonlinear coefficient was about 900, which was much larger than that of conven-tional ZnO varistor. Our previous work 5,18 also revealed that the dielectric and the varistor properties of TiO 2 -riched CCTO can be tuned by the addition content of TiO 2 . In this work, we prepared Mn-doped CCTO ͑CCMTO͒ ceramics and investigated their dielectric and non-Ohmic electric properties. The results revealed that the Mn doping can make the dielectric constant decrease about two orders ͑from 10 4 to 10

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