Synthesis and characterization of nanocrystalline mullite powders at low annealing temperature using a new technique

For the first time orthorhombic mullite nanoparticles (12 nm) have been synthesized via the co-precipitation technique using mixture of sodium aluminate and sodium silicate solutions as monophasic salts at low annealing temperature 1000 °C. The AC and DC electrical properties of the sintered mullite ceramics were investigated. The results indicated the precursor directly transformed to 3:2 molar ratio orthorhombic mullite. Meanwhile, the surface area of the produced o-mullite at 1000 °C was 15.1 m2/g which increased to 37.3 m2/g with addition of CTAB as a cationic surfactant. TEM images investigated that the microstructure was changed from rod-like shape to roughly spherical shape with addition of surfactant. The DC electrical resistivity of mullite sample sintered at 1600 °C was 16 times greater than that sintered at 1300 °C. The minimum dielectric loss value of 0.014 was obtained at 1600 °C sintering temperature at 1.5 MHz.