Abstract ▼

1. Synthesize the substituted Aurivillius phases and investigate the superconductivity and ferroelectric properties of the compounds.
2. Calculate the electronic structures of transition metal compounds to understand their physical properties.
1. Substitute Nb with Cr or Mo in $SrBi_2Nb

1. Synthesize the substituted Aurivillius phases and investigate the superconductivity and ferroelectric properties of the compounds.
2. Calculate the electronic structures of transition metal compounds to understand their physical properties.
1. Substitute Nb with Cr or Mo in $SrBi_2Nb_2O_9$ to make the metallic state with the $d^x$ (x>0) electronic configuration and investigate the superconductivity in the compounds. (1st year)
2. Analyze how are the lower lying atoms imaged brighter than the higher lying ones in the STM experiments for the $NbTe_2$ by examining the electronic structure of the compound. (1st year)
3. Investigate the change of the ferroelectric property in $SrBi_2Nb_2_-_xM_xO_9$ (M=Cr, Mo) with the amount of substitution. (2nd year)
4. Synthesize and characterize the physical properties of $AuNb_4P_2S_2_0$ by examining its electronic structure.
1. Partially doped Aurivillius phases $SrBi_2Nb_2_-_xM_xO_9$ (M=Cr and Mo) were successfully synthesized and characterized. The dielectric constants of substituted compounds were enlarged nevertheless Cr or Mo is substituted. The increment is bigger in the Mo substituted compound than in the Cr doped one although the ionic size difference between $Nb^5^+$ and of $Cr^6^+$ is much bigger than that between $Nb^5^+$ and $Mo^6^+$. Consequently, the dielectric constant of the substituted Aurivillius phase $Bi_2A_n_-_1B_n_-_xM_xO_3_n_+_1$ depends on the extent of distortion of the $BO_6$ octahedra and more strongly on the polarizability of the metal.
2. The new quaternary compounds $AuNb_4P_2S_2_0$ was prepared and characterized. The mixed valency such as $Au^+^1$ and $Au^+^3$, or $Nb^+^4$ and $Nb^+^5$, are expected. The XPS data tells us that the mixed valence state arises not on Au but on Nb only in $AuNb_4P_2S_2_0$, which is not found in $ANb_2PS_1_0$(A=Na, Ag). This conclusion is consistent with the results of the crystal structure of Au environment and projected density of states(PDOS) data.
3.The images of AFM or STM cannot tell that the brighter image represents the protruded atoms. For the accurate analysis, the electron density should be examined.
4. Through this work, S-Y. Moon has received her MS degree, and all results were published as follows: Bull. Korean Chem. Soc., 2001, 22, 499 Bull. Korean Chem. Soc., in press Chem. Mater., to be published.

목차 Contents

• I. 연구계획 요약문...3
• 1. 국문요약문...3
• II. 연구결과 요약문...4
• 1. 국문요약문...4
• 2. 영문요약문...5
• III. 연구내용...6
• 1. 서론...6
• 2. 연구방법 및 이론...11
• 3. 결과 및 고찰...14
• 4. 결론...18
• 5. 인용문헌...19