Microstructural and physical properties of magnesium oxide-doped silicon nitride ceramics

Silicon nitride based ceramics with aluminum, yttrium and magnesium oxides were produced by cold isostatic pressing and free sintering. The phase composition of the starting MgO powder obtained by the novel technology has been studied. The effect of magnesium oxide content on the structure of the produced materials has been investigated. It was found, that obtained materials with 1 and 2 wt.% of magnesium oxide and without it have a typical beta-silicon nitride structure with elongated grains. Ceramics with 5 wt.% magnesia has a duplex alpha/beta-structure with elongated and equiaxed grains. Ceramics with 2 wt.% magnesium oxide has a maximum density of 2.91 g/cm(3). The increases in magnesium oxide content upto 5% led to decrease in the shrinkage ( from 16% to 12%) and density ( from 2.88 to 2.37 g/cm(3)). (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).