الخلاصة:
The aim of this work is to prepared porcelain with high mechanical and dielectric properties by using economical native raw materials without providing ideal high-cost conditions. The basic porcelain composition was selected consisting of 30 wt% kaolin, 45 wt% potash-feldspar and 25 wt% quartz. It was prepared by sintering the mixture at different temperatures (1140–1260 °C).
The optimum sintering conditions gave a bulk higher density (2.41 g/cm3) and excellent
mechanical properties. The three point flexural strength, Vickers micro-hardness of porcelains were 205 MPa and 6.8 GPa, respectively. Dielectric measurements have been carried out at 1 KHz from room temperature to 200 °C. The dielectric constant, dielectric loss tangent, and resistivity of the porcelain sample sintered at 1160 °C were 25, 0.008 and 9 x 1013 .cm, respectively. So these values reveal that the porcelain is a good insulator. The mechanical and dielectric properties of porcelain are improved by addition of titanium oxide and zinc oxide. The addition of titanium oxide improved both mechanical and dielectrical properties. The optimum sintering conditions gave a higher bulk density (2.47 g.cm−3) and excellent mechanical properties. The three point flexural strength (3PFS), Vickers micro hardness of samples containing 5 wt TiO2 and sintered at 1160 °C were 238 MPa, 12.3 GPa , respectively. The dielectric constant, dielectric loss tangent of samples containing 5 wt TiO2 sintered at 1160 °C for 2 h were: 31,0.005, respectively. These values were permitted to confirm that this is typical insulating material. The mechanical properties of this latter may candidate it to be used in many fields and several applications. Moreover, the addition of zinc oxide improved both mechanical
and dielectric properties. The optimum sintering conditions gave excellent mechanical
properties: The three point flexural strength, Vickers micro hardness of samples containing
5wt ZnO and sintered at 1160 °C were 242 MPa, 14.5 GPa, respectively. But it did not have a significant impact on the dielectric properties. Besides, the maximum value of the three point flexural strength achieved for the samples containing 5 wt TiO2 and 5 wt ZnO are nearby that of the flexural strength of porcelain containing 5 wt% TiO2 and 30 wt % alumina (about 240 MPa). In other words, the presence of 30 wt % alumina in their product well confirm the benefic effect of the used raw materials (saving 30 wt % alumina) on porcelain strengthening.
