Phase Composition, Crystallite Size and Physical Properties of B2O3-added Forsterite Nano-ceramics

Abstract

This study was aimed to know the effect of B 2 O 3 addition on the phase composition, crystallite size and dielectric properties of forsterite (Mg 2 SiO 4 ) nano-ceramics. It utilized a purified silica sand from Tanah Laut, South Kalimantan as the source of (amorphous) silica and a magnesium oxide (MgO) powder. They were thoroughly mixed and milled prior to calcination. The addition of 1, 2, 3, and 4 wt% B 2 O 3 to the calcined powder was done before uniaxial pressing and then sintering at 950 °C for 4 h. The phase composition and forsterite crystallite size, the microstructure and the dielectric constant of the sintered samples were characterized using X-ray diffractometer (XRD), Scanning Electron Microscope (SEM) and Vector Network Analyzer (VNA), respectively. Results showed that all samples contained forsterite, periclase (MgO) and proto enstatite (MgSiO 3 ) with different weight fractions and forsterite crystallite size. In general, the weight fraction and crystallite size of forsterite increased with increasing B 2 O 3 addition. The weight fraction and crystallite size of forsterite in the 4%-added sample reached 99% wt and 164 nm. Furthermore, the SEM images showed that the average grain size became slightly larger and the ceramics also became slightly denser as more B 2 O 3 was added. The results are in accordance with density measurements using the Archimedes method which showed that the 4% ceramic exhibited 1.845 g/cm3 apparent density, while the 1% ceramic 1.681 g/cm 3 . We also found that the higher the density, the higher the average dielectric constant, i.e. it was 4.6 for the 1%-added sample and 6.4 for the 4%-added sample.

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