Crystallographic data of new superlattice phases for spinel LiMn2O4 at low temperatures
Crystallographic data of new superlattice phases for spinel LiMn2O4 at low temperatures
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尖晶石 LiMn2O4 低温下新超晶格相的晶体学数据
DOI：
10.1017/s0885715600010770
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发表时间：
2000
影响因子：
0.5
通讯作者：
E. Akiba
中科院分区：
文献类型：
--
作者：
H. Hayakawa;T. Takada;H. Enoki;E. Akiba
对尖晶石LiMn 2 O 4（室温下Fd 3 <$m）的低温粉末X射线衍射数据的广泛分析清楚地表明，发生了两种结构相变：第一种是在285 K左右从立方晶到正交晶，第二种是在65 K左右从正交晶到四方晶。在低于285 K的温度下，超晶格峰出现在衍射图案中，通过将尖晶石晶胞的a和B轴增加三倍而成功地索引。在250 K下，晶胞为面心正交晶系，Fddd，F2 dd或Fd 2d，其中a=24.855（1），B=24.755（2），c=8.2014（3）μ m，V=5046.1（4）μ m 3，Dx=4.284 g/cm 3，Z=72。在30 K下的晶胞参数为体心四面体I41/amd或I41/a，a=17.5176（3），c=8.1961（2）Ω，V=2515.1（1）Ω 3，Dx=4.298 g/cm ~ 3，Z=36。
Extensive analyses of low-temperature powder x-ray diffraction data for spinel LiMn2O4 (Fd3¯m at room temperature) make it clear that two structural phase transitions occur: first around 285 K from cubic to orthorhombic, second around 65 K from orthorhombic to tetragonal. At temperatures under 285 K, superlattice peaks appear in the diffraction pattern that were successfully indexed by tripling the a and b axes of the spinel unit cell. At 250 K, the unit cell is face-centered orthorhombic, Fddd, F2dd, or Fd2d, with a=24.855(1), b=24.755(2), c=8.2014(3) Å, V=5046.1(4) Å3, Dx=4.284 g/cm3, Z=72. The unit cell at 30 K was confirmed to be body-centered tetragonal I41/amd or I41/a, with a=17.5176(3), c=8.1961(2) Å, V=2515.1(1) Å3, Dx=4.298 g/cm3, Z=36.