X. M. Chen

Dielectric and nonlinear electrical behaviors observed in Mn-doped CaCu3Ti4O12 ceramic

We present a remarkable effect of Mn doping on the dielectric and nonlinear electric properties of CaCu3Ti4O12 ceramics. The results indicate that only 2.5at.% Mn doping can suppress the dielectric permitivity in CaCu3Ti4O12 by up to two orders of magnitude (from 104 to 102), 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.

Effects of Sr2Nb2O7 additive on microstructure and mechanical properties of 3Y–TZP/Al2O3 ceramics

Abstract The effects of Sr 2 Nb 2 O 7 additive on microstructure and mechanical properties of 3Y–TZP/Al 2 O 3 ceramics were investigated. Sr 2 Nb 2 O 7 reacted with Al 2 O 3 to form SrAl 12 O 19 platelets, which could contribute to the fracture toughness due to the elongated grains. The fraction of transformable tetragonal zirconia phase increased firstly with the Sr 2 Nb 2 O 7 content and then decreased when the additive content is beyond a critical value. Also, the fracture toughness increased firstly to a maximum value (10.2 MPa.m 1/2 ) with the additive content and then decreased for composites sintered at 1600 °C for 6 h, while it increased linearly with additive content for composites sintered at 1575 °C for 6 h. However, the Vickers hardness decreased linearly with the Sr 2 Nb 2 O 7 content for composites sintered under any condition investigated here. The fracture toughness was affected by the fraction of transformable tetragonal zirconia phase and Sr 2 Nb 2 O 7 content, and the toughening effects should be the integrated result of stress-induced transformation toughening and elongated grain toughening.

Contribution of Electron Hopping on Colossal Dielectric Response of Bi-Substituted LaMnO3 Ceramics

The dielectric properties and conductivity of semiconducting Bi-substituted LaMnO 3 ceramics were investigated. It was found that the electron hopping between Mn 3 + and Mn 4 + contributed to the colossal dielectric response of Bi-substituted LaMnO 3 ceramics. A dielectric relaxation with the same activation energy of conductivity was observed in the temperature range from 120 K to 240 K. Due to the effects of the lone-pair electron of Bi 3 + , the activation energy of the dielectric relaxation in La 1 − x BixMnO 3 ceramics increased with increasing amount of Bi3 +.

BaTiO3 ceramics toughened by dispersed coarse particles

Abstract A new approach was proposed and investigated for toughening BaTiO3 ceramics, where coarse BaTiO3 particles were incorporated and dispersed into the fine-grained matrix. The fracture toughness was enhanced significantly by increasing the content of coarse BaTiO3 particles and reached the maximum of 2.0 MPam1/2, while that of the matrix was 1.1 MPam1/2. The piezoelectric properties showed slight variation in comparison to the reference BaTiO3 ceramics.

Temperature-stable dielectric ceramics in Pb(Mg1/3Nb2/3) O3-CaTiO3-Bi4Ti3O12 pseudo-ternary system

Abstract Ceramics in the Pb(Mg 1/3 Nb 2/3 )O 3 –CaTiO 3 –Bi 4 Ti 3 O 12 pseudo-ternary system were investigated to search for new temperature-stable dielectrics for high frequency applications. A near-zero temperature coefficient was obtained combined with a high dielectric constant (124) and a low dielectric loss (10 −3 at 1 MHz) where a complex phase constitution was observed. The dielectric properties were significantly sensitive to the sintering conditions due to the variation of phase constitution.