Influence of glass addition and sintering temperature on the structure,mechanical properties and dielectric strength of high-voltage insulators

Soda-lime glass as a substituent for the feldspar was used to prepare high-tension electrical porcelain by standard chemical solid reaction technique. The effect of glass substitution and sintering temperature on the physical properties, microstructure, hardness, modulus of rupture, flexural strength and Dielectric breakdown strength were examined. Zero water absorption (WA %) and apparent porosity (AP %) were achieved for the samples with glass content >15 wt.% sintered at 1100 °C. The apparent density was found to increase with sintering temperature. The Vicker’s micro-hardness increased with both glass addition and sintering temperature. Both of the modulus of rupture (MOR) and flexural strength (σ_f) had maxima values at 15 wt.% glass addition. The structure and morphology were characterized by X-ray diffraction and scanning electron microscope (SEM). It showed the formation of mullite needles at sintering temperature of 1100 °C, which enhanced the mechanical and electrical properties of the porcelain. The dielectric breakdown strength increased with sintering temperature and glass addition. The highest dielectric strength was found at 10 wt.% of glass addition depending on the Na₂O and Fe₂O₃ content.