Study on Synthesis and Crystal Structure of Rare-Earth Calcium Silicate

在目前的研究中，CaO-Y_2 O_3-SiO_2备用系统被拆除。在这个备用系统中，已报告了Ca_2Y_8Si_6O_<26>、Ca_3Y_6Si_6O_和<24>Ca_4Y_6Si_6O_的组合物<25>。这表明了apatite-type compounds的组成并没有被证实。Ca_2Y_2Si_2O_9已经携带了一种吡啶型结构，但晶体学数据尚未被报道。一般来说，硅有许多同位素，形成许多复杂的结构。由于这一原因，新结构预计在这种多分量系统中产生新的化合物。在CaO-Y_2 O_3-SiO_2交替系统中，该化合物在Ca_2Y_8Si_6O_<26>（apatite型结构）、Ca_2Y_2Si_2O_9 （cuspidine型结构）、Ca_3Y_2Si_3O_<12>（silico-carnotite型结构）和Ca_3Y_2Si_6O_<18>（新结构）上准备在Ca_2Y_8Si_6O_（新结构）上产生单相位结构<26>。This phase is hexagonal， a=b=0.9341（1）， c=0.6788（1）nm。Ca_3Y_6Si_6O_2<24>报告了两个相位、Ca_2Y_8Si_6O_和CaSiO_3的apatite-type化合物<26>的组成的样本。在Ca_4 Y_6 Si_6 O_<25>consisted of Ca_2 Y_8 Si_6 O_<26>and Ca_3 Y_2 Si_3 O_中准备的样本<12>。1 t确认Ca_2Y_2Si_2O_9具有一种异黄酮型结构（单线性P2_l/c， a=0.74468（3）， b=1.049240（3）， c= 1.09661 （4）nm， β=110.170（3））。新化合物Ca_3Y_2Si_3O_<12>_与硅碳铁矿（Ca_5（PO_4）_2SiO_4）的异构结构。Ca_3Y_2Si_3O_is <12>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））由ternary SiO_4环组成。

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.