论文部分内容阅读
用固态烧结法合成了新化合物Ca_2FeWO_6。 用差热分析和X射线物相分析等方法,研究了新化合物Ca_2FeWO_6的相变,证明该化合物在(706±5)℃存在一级位移型相变。低温相α-Ca_2FeWO_6,属正交晶系,空间群为Pmm2,室温时点阵常数为:a=0.770 5l nm,b=0.542 42 nm和c=0.551 08 nm。测量密度为D_m=6.04g/cm~3,单位晶胞内具有2个化学式量。高温相β-Ca_2FeWO_6,属立方晶系,空问群为Fm3m,在750℃时的点阵常数为a=0.780 8 nm,z=4。计算密度为D_x=5.802 g/cm~3。并用X射线多晶法分别测定了α-Ca_2FeWO_6和β-Ca_2FeWO_6的晶体结构。详细地阐明了相变机理。
A new compound Ca_2FeWO_6 was synthesized by solid state sintering. The phase transition of the new compound Ca_2FeWO_6 was studied by means of differential thermal analysis and X-ray phase analysis. It was found that there was a first-order phase transition at (706 ± 5) ℃. The low temperature phase α-Ca 2 FeWO 6 belongs to the orthorhombic system with space group Pmm2. The lattice constants at room temperature are: a = 0.770 5l nm, b = 0.542 42 nm and c = 0.551 08 nm. The measurement density is Dm = 6.04g / cm ~ 3, and there are two chemical formulas in unit cell. The high-temperature phase β-Ca 2 FeWO 6 belongs to the cubic crystal system with the space group Fm3m and the lattice constant at 750 ℃ is a = 0.780 8 nm and z = 4. The calculated density is Dx = 5.802 g / cm ~ 3. The crystal structures of α-Ca 2 FeWO 6 and β-Ca 2 FeWO 6 were measured by X-ray polycrystalline method. The phase transition mechanism is explained in detail.