| Research Abstract |
We chose a cubic pollucite, CsAlSi_2O_6, as a template compound, and report that the cubic Cs-leucite compounds with various chemical compositions can be synthesized by multi-step heating process as a solid-state reaction method, and that the thermal expansion properties in the range 298-1273K for all of the synthesized compounds were examined by using low- and high-temperature XRD.
The results obtained can be summarized as follows.
1. Cubic Cs-leucite compounds ; Cs-leucites : CsMSi_2O_6(M=B,Al,Fe,B_<0.2>Al_<0.8>,Al_<0.5>Fe_<0.5>,Al_<0.2>Fe_<0.8>), Cs_2MSi_5O_<12>(M=Cd,Fe,Mg,Ni,Zn), Cs-Na-leucites : Cs_<1-X>Na_XASI_2O_6(X=0.1,0.2), Cs_<0.9-XNa_X>Al_<0.9>Si_<2.1>O_6(X=0.1,0.2), and RbAlSi_2O_6, can be successfully synthesized by the multi-step heat treatment.
Their crystal structures, as determined by XRD analysis, were found to belong to space group Ia-3d of the cubic crystal system in the range 298-1273K.
2. The thermal expansion rates of the synthesized cubic Cs-leucite compounds were clearly varied with the chemical composition of Cs-leucite compounds. In addition, the effect of the substitution of alkaline metalion of which ionic radius was smaller than Cs^+ ion led to the enhanced low thermal expansion rates of the cubic Cs-lecuite compounds.
3. The thermal expansion rates of the cubic Cs-leucite compounds ; Cs-leucites, Cs-Na-leucites and Cs-Li-leucites were changed by not only the amount of Cs^+ ions but also the space ratio owing to the difference of the cation size between Cs^+ ions and Na^+ or Li^+ ions.
4. The Windows95/98/NT application softwares can use the CIF as the crystal structure data was developed to simplify a display of complex crystal structure such as silicate compounds using the coordination polyhedron.
5. The thermal expansion rates of the synthesized cubic Cs_<0.8>Li_<0.1Al_<0.9>Si_<2.1>O_6 and Cs_<0.7>Li_<0.2>Al_<0.9>Si_<2.1>O_6were 0.11% at 1173K and 0.081 % at 1073K, which were lower than that of Cs_<0.9>Al_<0.9>Si_<2.1>O_6, 0.2 % at 1273K.
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