单斜晶系
四方晶系
结构精修
中子衍射
结晶学
氟化物
离子
相变
间质缺损
晶体结构
化学
萤石
材料科学
分析化学(期刊)
兴奋剂
无机化学
凝聚态物理
物理
光电子学
色谱法
有机化学
作者
Ryoji Kanno,Kouji Ohno,Heather K. Izumi,Y. Kawamoto,Takashi Kamiyama,Hajime Asano,Fujio Izumi
标识
DOI:10.1016/0167-2738(94)90319-0
摘要
Tetragonal PbSnF4 synthesized by a solid-state reaction at 523–573 under an HF gas atmosphere showed a transition to a monoclinic phase between 20 and 77 K. Its structural changes were studied at 20–300 K using the Rietveld analysis of TOF neutron diffraction data. The structure of PbSnF4 is basically composed of the fluorite lattice and the cationic framework made up of layers perpendicular to the c-axis with a sequence of PbPbSnSn. At 20 K, the monoclinic structure has no fluoride io ns on the (11) tetrahedral site which is situated between two Sn layers. The interstitial F(4) site situated between Sn and Pb layers splits into two sites near a large cavity in an F8 cube. Three sites split into four at 170 and 300 K; the change in the interstitial structure corresponds to the monoclinic-to-tetragonal phase transition. Above 170 K, fluoride ions at the F(2) tetrahedral site migrate gradually to the F(1) site. A gradual slope change in the conductivity versus temperature curve around room temperature corresponds to the migration of fluoride ions.
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