Effect of CaO addition on the densification and conductivity of 10NiO-NiFe_2O_4 composite ceramics

The effect of CaO content,in the range from 0 % to 4 %,and sintering temperature on the phase composition and relative density and electrical conductivity of CaO doped 10NiO-NiFe2O4 composites were studied.The results showed that the composites consisted of NiO phase and NiFe2O4 phase.There was apparent oxygen absorbing and releasing behavior observed during the heating process tested in air for 10NiO-NiFe2O4 composites.Introduce of CaO could accelerate the densification of 10NiO-NiFe2O4 composites.The maximum value of relative density with 98.75% for sample doped 2%CaO,which sintered at 1 200 ℃,was beyond about 20% for the undoped composites.The electrical conductivity of composites sintered at 1 200 ℃ markedly depended on the CaO content.As the CaO content was from 0 to 1 %,the conductivity abruptly decreased with one or two magnitude at the temperature between 500 ℃ and 650 ℃,As the CaO content was from 2 % to 4 %,the conductivity increased with increasing the temperature.The maximum conductivity at 960 ℃ with 16.29 S/cm was obtained for composites doped 2 % CaO.