Influence of layer thickness on microstructure and dielectric properties of Mg2TiO4 microwave ceramics fabricated by vat photopolymerization

The dielectric properties of microwave ceramics fabricated via additive manufacturing (AM) are generally lower than those of traditional dry-pressed ones. It is most likely attributed to the special laminated manufacturing method. In order to clarify this phenomenon, the vat photopolymerization technique was applied to fabricate crack-free Mg2TiO4 ceramics by measuring manufacturing error of green bodies to determine the lower threshold value of exposure parameters. Under the condition of low power densities of 7.7-11 mW/cm(2) and short exposure time of 0.8 s, the vat-photopolymerized Mg2TiO4 samples with manufacturing error of 12-31 mu m were achieved. When the layer thickness increased from 20 to 50 mu m, the number of laminated interfaces decreased by half, resulting in the obvious decrease in the number of pore defects along the laminated interface. Consequently, during the final stage of sintering, the number of pores needed to be excluded from the Mg2TiO4 green bodies fabricated with the layer thickness of 40 and 50 mu m was less than that fabricated with the layer thickness of 20 and 30 mu m. Additionally, the grain growth of Mg2TiO4 ceramics prepared with a larger layer thickness would proceed fully due to the weak inhibition from the less pores. Therefore, the relatively dense microstructure and fully grown grains contributed to the increase of quality factor values from 123,000 to 142,000 GHz as the layer thickness increased from 20 to 40 and 50 mu m.