Mn
2+-substituted cordierite solid solutions (Mg
2(1-X) Mn
2XAl
4Si
5O
18,
X≤0.6) with a hexagonal crystal structure were prepared by solid state reaction. Expansion in the a-axis direction and contraction in the c-axis direction with increasing Mn
2+-substitution were caused by flattening deformation of MgO
6 octahedra. The lattice parameters for
X=0.6 were
a=0.939nm and
c=0.929nm. The sintering temperature for densification lowered with increasing Mn
2+-substitution. Ceramics with 99% relative density were obtained at 1430°C for
X=0, at 1330°C for
X=0.25 and at 1230°C for
X=0.6. The mean linear thermal expansion coefecients were (0.9-1.1)×10
-6°C
-1 (20-800°C). Infrared radiation emissivities of ceramics increased with increasing relative density at surface temperatures 100-400°C in the wave length range of 2.5-14.5μm. Thus, the Mn
2+-substituted cordierite solid solutions with the theoretical density can be used as infrared radiation ceramics with low thermal expansion coeffiecients.
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