| Co-Investigator(Kenkyū-buntansha) |
KUBOTA Shun-ichi Institute for Advanced Materials Processing, Tohoku University, Research Associate, 素材工学研究所, 助手 (10271975)
YAMANE Hisanori Institute for Advanced Materials Processing, Tohoku University, Associate Professor, 素材工学研究所, 助教授 (20191364)
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| Research Abstract |
In the present study, CaO-Y_2O_3-SiO_2 ternary system was taken up. In this ternary system, apatite-type structure compounds have been reported at the compositions of Ca_2Y_8Si_6O_<26>, Ca_3Y_6Si_6O_<24> and Ca_4Y_6Si_6O_<25>. It was pointed out that the composition of apatite-type compounds had not been established. The preparation of Ca_2Y_2Si_2O_9 having a cuspidine-type structure was carried out, but the crystallographic data has not been reported yet. Generally, silicates have many isomorphs and form many complicated structures. For this reason, new compounds having new structure are expected in this multicomponent system.
In CaO-Y_2O_3-SiO_2 ternary system, the compounds prepared by reaction sintering at 1700K were Ca_2Y_8Si_6O_<26> (apatite-type structure), Ca_2Y_2Si_2O_9 (cuspidine-type structure), Ca_3Y_2Si_3O_<12> (silico-carnotite-type structure) and Ca_3Y_2Si_6O_<18> (new structure).
A single-phase having an apatite-type structure was prepared at Ca_2Y_8Si_6O_<26>. This phase is hexagonal, a=b=0.9341(1), c=0.6788(1)nm. The sample with the composition of Ca_3Y_6Si_6O_<24> which was reported as apatite-type compound was two phases, Ca_2Y_8Si_6O_<26> and CaSiO_3. The sample prepared at the composition of Ca_4Y_6Si_6O_<25> consisted of Ca_2Y_8Si_6O_<26> and Ca_3Y_2Si_3O_<12>. 1t was confirmed that Ca_2Y_2Si_2O_9 had a cuspidine-type structure (monoclinic P2_l/c, a=0.74468(3), b=1.049240(3), c= 1.09661 (4)nm, β=110.170(3)゜).
The new compound, Ca_3Y_2Si_3O_<12> is isostructual with silico-carnotite (Ca_5(PO_4)_2SiO_4). Ca_3Y_2Si_3O_<12> is orthorhombic P nma, a=0.65574(2), b=1.56066(3), c=1.00399(2)nm. Ca_3Y_2Si_6O_<18> (monoclinic C2/c, a=1.33422(5), b=0.77320(3), c=1.47959(6)nm, β=90.263(3)゜) is composed of ternary SiO_4 rings.
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