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Preparation of Bi_(4)Ti_(3)O_(12)(BIT)Ceramics via a High-energy Ball Milling Process doped with Multi-Walled Carbon Nanotubes(MWNTs)

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Materials Sciences and Applications 2013年第9期4卷 549-555页

作者： Alexandre Goncalves Pinheiro Gilberto Dantas Saraiva Josué Mendes Filho Antonio Sergio Bezerra Sombra faculdade de educacao ciencias e letras do sertao central Universidade Estadual do CearáQuixadáBrazil departamento de Fisica Universidade Federal do CearáFortalezaBrazil

We prepared the Nano-sized bismuth titanate Bi4Ti3O12 (BIT) powders, through a high-energy ball milling process from their oxides Bi2O3 and TiO2. This BIT phase can be formed after a milling process for 40 min. With an increasing milling time, this particle size of mixture is gradually reduced, thus, we have mostly an amorphous phase. The BIT ceramics were duly obtained by sintering the synthesized powders at temperatures ranging from 850°C to 1000°C. The BIT ceramics sintered at 1020°C for 1 h, exhibiting a density with 7.52 g/cm3 of a crystaline phase and a dielectric of K = 288.11 (100 Hz), as well as a dielectric loss of 0.05 (100 kHz). The High-energy ball milling process is a promising way to prepare BIT ceramics. After the preparation of the BIT, we doped it with the Multi-Walled Carbon Nanotubes which are properly obtained by a chemical vapour deposition (CVD), using nickel as a catalyst, as well as using acetilene at 720°C, and then proceeded with the dielectric and optical measurements.

关键词： Bi_(4)Ti_(3)O_(12) Ceramics Ferroelectric High-energy Ball Milling Sintering Carbon Nanotubes MWNT

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HIGH THeRMAL STABILITY OF MICROWAVe DIeLeCTRIC PROPeRTIeS OF CaTi_(1-x)(Nb_(1/2)Fe_(1/2))_(x)O_(3)CeRAMICS

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Journal of Advanced Dielectrics 2011年第4期1卷 417-427页

作者： A.D.S.BRUNO COSTA M.C.ROMeU R.C.S.COSTA T.S.M.FeRNANdeS F.W.de O.AMARANTe M.A.S.DA SILVA G.D.SARAIVA A.S.B.SOMBRA Laboratorio de Telecomunicacoesoe Ciencia eengenharia dos Materiais(LOCeM)departamento de Fisica Universidade Federal do CearaCaica Postal 6030CEP 60455-760FortalezaCearaBrazil departamento de engenharia de Teleinformatica CP 6007 Universidade Federal do Ceara CEP 60455-760FortalezaCearaBrazil faculdade de educacao ciencias e letras do sertao centraluniversidade estadual do ceara Quirada-CE63.900-000Brazil

This paper presents a study of the structure and microwave properties of Nb_(1/2)^(5+)Fe_(1/2)^(3+) substituted into the Ti4t site of calcium titanate *** structural and dielectric properties of solid solutions in CaTi_(1-x)(Nb_(1/2)Fe_(1/2))_(x)O_(3),was *** microwave dielectric properties of solid solutions in CaTi_(1-x)(Nb_(1/2)Fe_(1/2))_(x)O_(3),(CNFTOX with x=0.1 to x=1)is *** modified CaTiO_(3)(CTO)ceramics were prepared by a new procedure in the solid-state method.A study of the variations of the ball-milling process was *** calcinations were done at 900C for 3 and 5 h respectively,and the sintering at 1100℃,for 3 *** structural property studies of the ceramics were investigated by X-ray di®raction(XRD)and Raman *** X-ray analysis showed that all samples have an orthorhombic *** renement analysis of all samples were also duly performed and *** nine scattering bands centered at 183,227,247,288,338,470,490 and 805 cm^(-1) were *** peaks presented a small shift as a function of the x *** Raman spectra in the studied samples showed a small band at 805 cm^(-1),which is a function of the x *** dielectric permittivity and loss at microwave frequencies(MW)were *** both calcination treatments(900℃for 3 and 5 h),the dielectric permittivity decreased with a decrease of the titanium *** permittivity values in the range of 20 to 80 were *** was also observed that a higher number of balls in the milling process contribute to the increase of theεr *** CNFTO has an excellent microwave property at x=0.6,with a temperature coe±cient of resonant frequency(Tf)near zero(Tf=2.8ppm/℃).

关键词： Ceramics dielectric permittivity

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eFFeCT OF IMPURITIeS ON THe DIeLeCTRIC PROPeRTIeS OF OLeIC ACID

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Journal of Advanced Dielectrics 2012年第3期2卷 47-54页

作者： F.F.de SOUSA P.T.C.FReIRe J.MeNdeS FILHO A.C.OLIVeIRA e.LONGHINOTTI P.H.M.de VASCONCeLOS G.D.SARAIVA S.G.C.MOReIRA P.ALCANTARA Jr. faculdade de Cincias exatas e Naturais universidade Federal do Para CEP 68.507-970 Maraba-PABrazil departamento de Fisica Universidade Federal do Ceara CEP 60.455-760Fortaleza-CEBrazil universidade Federal do ceara Campus do Pici-Bloco 940 Langmuir Lab.de Adsorcao e Catalise CeP 60.000-000 Fortaleza-CEBrazil faculdade de educacao ciencias e letras do sertao central universidade estadual do ceara CEP 63.900-000 Quixada-CEBrazil faculdade de Fisica Universidade Federal do Para CEP 66.075-110Belem-PABrazil

Temperature dependence of the dielectric constant of oleic acid with different degrees of puritywas measured in the 233-313 K *** was observed that the presence of impurities(palmiticand linolenic acids)strongly influences the dielectric constant,melting point and dipole moment of the oleic *** values of apparent dipole moment and the Kirkwood correlation parameterswere evaluated using the Kirkwood's model and were estimated to be about 1.20,1.61 and 2.27 D,respectively for 60,90 and 97 wt%oleic acid.

关键词： Oleic acid dielectric properties fatty acids Kirkwood's theory.

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