Compaction pressure effect on the dielectric, DC and AC conductivity of C-130 porcelain

Abstract

Porcelain insulators can be prepared in a variety of compositions using several different preparation techniques. In the frame of the present work the effect of the applied compaction pressures on the C-130 grade electroporcelain was studied in terms of electrical and dielectric properties. Compaction is a widely used preparation process, nevertheless, a little is known about the effect of the compaction pressure on the final electrical properties of the material. Samples prepared with different compaction pressures (from 70 MPa to 110 MPa; 10 MPa step size) were subjected to a measurement of DC conductivity up to 1200 °C, and a measurement of dielectric properties at room temperature after different firing temperatures. The DC conductivity of the raw samples ranged from ∼10−10 S/m at room temperature to <10−3 S/m at 1100 °C. Temperature dependence of the DC conductivity revealed that the dominant charge carriers were H+ and OH− ions (initial stages of heating) and alkali ions (at high temperatures and during second heating). The DC conductivity of the previously fired samples (at 1100 °C) ranged from ∼10−12 S/m (room temperature) to ∼10−3 S/m (1200 °C). The AC conductivity of the samples ranged from ∼10−7 S/m (samples fired at 1300 °C, measured at low frequencies) to ∼10−3 (raw sample, measured at high frequencies). AC conductivity measurements and dielectric analysis confirmed that the conduction occurred through ion hopping and the bulk boundary conductivity was dominant. The relative permittivity reached 7–8 after firing at 1300 °C at frequencies above 2 MHz.