The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and ...The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases(40 < f < 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.展开更多
We investigate the dopant site selectivity of CaCu_(3)Ti_(4)O_(12)(CCTO)using the first principles calculations.Our results show that,for four cases of possible occupancy by La atom,lattice expansions and formation en...We investigate the dopant site selectivity of CaCu_(3)Ti_(4)O_(12)(CCTO)using the first principles calculations.Our results show that,for four cases of possible occupancy by La atom,lattice expansions and formation enthalpies with different dopant quantities indicate that doped La cations are preferentially substituted for Ca sites in CaCu_(3)Ti_(4)O_(12),which is excellent in agreement with the experimental observation(Choi et al.Adv.Mater.21(2009)885).Furthermore,more interesting information of doping is also explored by the analysis of density of states and it is found that La substituting for Cu may advance the electron conduction in CCTO.It supplies a potential solution for limitations of CCTO devices by exploring the effect when La substitutes for Cu sites in the CCTO crystal.展开更多
文摘The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases(40 < f < 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11074017 and 51032002the IHLB(No PHR201007101),the Beijing Nova Program(No 2008B10)+1 种基金the Beijing Natural Science Foundation(No 1102006)the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the Ministry of Education.
文摘We investigate the dopant site selectivity of CaCu_(3)Ti_(4)O_(12)(CCTO)using the first principles calculations.Our results show that,for four cases of possible occupancy by La atom,lattice expansions and formation enthalpies with different dopant quantities indicate that doped La cations are preferentially substituted for Ca sites in CaCu_(3)Ti_(4)O_(12),which is excellent in agreement with the experimental observation(Choi et al.Adv.Mater.21(2009)885).Furthermore,more interesting information of doping is also explored by the analysis of density of states and it is found that La substituting for Cu may advance the electron conduction in CCTO.It supplies a potential solution for limitations of CCTO devices by exploring the effect when La substitutes for Cu sites in the CCTO crystal.
