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Journal of the Korean Ceramic Society 2001;38(11): 962. |
| Crystal Structure of High Temperature Phase in ${Bi_2}{O_2}$-layered Perovskites ${ABi_2}{M_2}{O_9}$(A=Pb, Sr, M=Nb, Ta) |
| Jeong-Seog Kim, Chae-il Cheon, Chang-Hee Lee1, Woong-Gil Choo2 |
Department of Materials Science and Engineering, Hoseo University
1Department of Neutron Physics, Hanaro Center, KAERI
2Department of Materials Science and Engineering, KAIST |
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| ABSTRACT |
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Crystal structure of PbBi$_2$Nb$_2$$O_{9}$ and $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ were determined by Rietveld method using neutron diffraction data in the temperature range of 300 K~1273K. Phase transition temperature were measured from the dielectric permittivitytemperature curve. The PbBi$_2$Nb$_2$$O_{9}$ showed a phase transition at about 810 K. In the Sr-excess compound $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ the phase transition was suppressed down to room temperature. Several structural models were tested by the Rietiveld refinement. Based on the `R` values and the structural parameters, the B2cb model is judged to be the most feasible one for the high temperature phase at above 810 K of the PbBi$_2$Nb$_2$$O_{9}$. The $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ sample was refined to show the most reliable results by the Am2m model.sults by the Am2m model. |
| Key words:
Paraelectric phase, Neutron diffraction, Crystal structures, SBT, $PbBi_2$${Ta_2}{O_9}$ |
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