Ba_2CdMoO_6及新化合物—Sr_2CdMoO_6晶体结构的研究

INVESTIGATION OF Ba_2CdMoO_6 AND A NEW COMPOUND Sr_2CdMoO_6 CRYSTAL STRUCTURES

自从对Sr_2CaWO_6的相变和晶体结构研究以后,引起了我们对该类型化合物A_2~ⅡB~ⅡB~ⅥO_6的兴趣(A~Ⅱ=Ba^(+2),Sr^(+2);B~Ⅱ=Ca^(+2),Cd^(+2),Fe^(+2),Co^(+2),…;B~Ⅵ=W^(+6),Mo^(+6)),它们属于复杂的钙钛矿型结构,且具有一定的规律性。据文献[2]报导Ba_2CaWO_6属立方晶系,而文献[1]报导Sr_2CaWO_6低温相属正交晶系。在元素周期表中Mo和W同属于ⅥB族,它们的化学性质相似,二元素的离子半径也非常相近,Cd和Ca虽不同族,但离子半径很相近,化合价相同。为此,本文用Mo^(+6)代替W^(+6),Cd^(+2)代替Ca^(+2)来研究Ba_2CdMoO_6和Sr_2CdMoO_6的晶体结构。文献[3]对Ba_2CdMoO_6做了简单的报导,但Sr_2CdMoO_6则未见报导。

The crystal structure of Ba_2CdMoO_6 have been investigated by means of X-ray powder method, precise measurement of lattice parameters and other methods,using specimens prepared by solid state sintering method. We confirmed Ba_2CdMoO_6 belonging to cubic system at room temperature, with space group Fm3m. And we obtained that the lattice parameter is a=8.3354(?) at room temperature. Simultaneously we defined that Sr_2CdMoO_6 is new compound, it belongs to orthorhombic system and the lattice parameters: a=8.1931(?), b=5.7694(?) and c=5.8406(?) at room temperature, The space group may be P_(mm2).