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Influence of bond valence on bond covalency in calcium doped lanthanum chromite

Chinese Journal of Chemistry 1999年第2期17卷 108-113页

作者：武志坚孟庆波张思远 laboratory of Rare Earth Chemistry and Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin 130022 Chinalaboratory of Rare Earth Chemistry and Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin 130022 Chinalaboratory of Rare Earth Chemistry and Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin 130022 China

The influence of bond valence on bond covalence in Lal-xCaxCrO3(x = 0.0, 0.1, 0.2, 0.3) has been studied by using semi empirical method. This method is the extortion of the dialectic description theory proposed by Phillips, Van Vetches, Levine and Tanaka (PVLT). In the calculation of bond valence, two schemes were adopted. The first is the equal-valence scheme, and the second is bond valence Sums (BVS) scheme. Bath schemes suggest that for the title compound bond covalence be mainly influenced by bond valence, and insensitive to the Ca doping level. Generally speaking, larger bond valences usually result in higher bond covalence's.

关键词： bond covalence bond valence Lal-xCaxCrO3 semi empirical method

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The Influence of bond valence on bond Covalency in RMn_2O_5 (R=La, Pr, Nd, Sin, Eu)

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Chinese Chemical Letters 1999年第1期10卷 91-94页

作者： Zhi Jian WU Si Yuan ZHANG(Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022) Changchun Inst. of Applied Chemistry Chinese Academy of Sciences Changchun 130022 China

The relationship between bond valence and bond covalency in RMn2O5 (R = La, Pr, ***, Eu) has been investigated by a semiempirical method. This method is the generalization of thedielectric description theory of Phillips. Van Vechten, Levine and Tanaka scheme. The resultsindicate that larger valences usually result in higher bond covalencies, in good agreement with thepoint that the excess charge in the bonding region is the origin of formation of bond *** factors, such as oxidation state of elements, only make a small contribution to bondcovalency.

关键词： bond valence bond covalency semiempirical method RMn_2O_5

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Understanding microwave dielectric properties of (1-x)CaTiO3-xLaAlO3 ceramics in terms of A/B-site ionic-parameters

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Journal of Advanced Ceramics 2017年第1期6卷 20-26页

作者： Dou, Zhanming Wang, Gan Jiang, Juan Zhang, Fan Zhang, Tianjin Hubei Univ Minist Educ Hubei Collaborat Innovat Ctr Adv Organ Chem Mat Key Lab Green Preparat & Applicat Funct Mat Wuhan 430062 Peoples R China Hubei Univ Sch Mat Sci & Engn Wuhan 430062 Peoples R China

We prepared (1-x)CaTiO3-xLaAlO3 (0 ≤x≤ 1) microwave dielectric ceramics using a conventional two-step solid-state reaction method,and investigated microwave dielectric properties of the ceramics in terms of A/B-site ***-parameters such as ionic polarizability,A-site bond valence,and ionic rattling were linked to the microwave dielectric *** the LaAlO3 content x in the (1-x)CaTiO3-xLaAlO3 ceramics increased from 0.3 to 0.7,the dielectric constant gradually decreased,which was attributed to the decrease of polarizability deviation and suppression of the cation *** temperature coefficient of the resonant frequency decreased as the content of LaAlO3 increased because of the increase of A-site cation bond *** quality factor value (Q × f) increased as LaAlO3 content increased because of the enhancement of the order degree of B-site cation.A significant deterioration of the temperature coefficient of the resonant frequency and Q ×fvalue was observed at the composition x =*** decreases were attributed to a phase transition from orthorhombic crystal (for x ≤ 0.5) to rhombohedral crystal (for x ＞ 0.5).

关键词： (1-x)CaTiO3-xLaAlO3 (CTLA) microwave dielectric ceramics ionic polarizability bond valence cation rattling effect

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DEPENDENCE OF MICROWAVE DIELECTRIC PROPERTIES ON STRUCTURAL CHARACTERISTICS OF ILMENITE,TRI-RUTILE AND WOLFRAMITE CERAMICS

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Journal of Advanced Dielectrics 2011年第1期1卷 127-134页

作者： EUNG SOO KIM CHANG JUN JEON Department of Materials Engineering Kyonggi University 94-6 Yiei-dongYoungtong-gu Suwon443-760Korea

Effects of crystal structures on dielectric properties of ATiO_(3)(trigonal ilmenite),ATa_(2)O_(6)(tetragonal tri-rutile)and AWO_(4)(monoclinic wolframite)(A=Ni,Mg,Co)ceramics with A-and B-site oxygen octahedra were investigated at microwave *** dielectric constant(K) of the specimens was affected by the dielectric polarizabilities of composition and cation bond valence between octahedral cation and oxygen ion per molar volum(V_(m)).The quality factor(Qf)of ATiO_(3)was appreciably larger than those of ATa_(2)O_(6)and AWO_(4)due to the different sharing types of oxygen *** temperature coe±cient of resonant frequency(TCF)of the specimens was dependent on the octahedral distortion per V_(m).

关键词： Microwave dielectric properties dielectric polarizabilities bond valence octahedral distortion

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