ORCID Profile
0000-0001-7413-1087
Current Organisation
Universidade Federal de Minas Gerais
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Publisher: American Chemical Society (ACS)
Date: 09-12-2005
DOI: 10.1021/CM051982F
Publisher: Elsevier BV
Date: 07-2007
Publisher: AIP Publishing
Date: 05-05-2005
DOI: 10.1063/1.1897065
Abstract: Complex perovskite-type Ca5−xSrxA2TiO12[A=Nb,Ta] (0⩽x⩽5) ceramics were prepared by conventional solid-state ceramic route. The crystal structure, microwave dielectric properties, and vibrational spectroscopic characteristics of these materials are reported. The structure and microstructure were investigated by x-ray diffraction and scanning electron microscopy techniques. The microwave dielectric properties were measured in the 3–5-GHz frequency range by the resonance method. Structural evolutions from orthorhombic to an averaged pseudocubic phase, with associated changes in dielectric properties, were observed as a function of composition. The structure-property relationships in these ceramics were established using Raman and Fourier transform infrared spectroscopic techniques. Raman analysis showed characteristic bands of ordered perovskite materials, with variation in both intensity and frequency as a function of composition.
Publisher: American Chemical Society (ACS)
Date: 21-11-2007
DOI: 10.1021/CM7024747
Publisher: Elsevier BV
Date: 2007
Publisher: Wiley
Date: 13-11-2009
DOI: 10.1002/JRS.2494
Publisher: AIP Publishing
Date: 15-10-2005
DOI: 10.1063/1.2112179
Abstract: Complex ceramics Ca5−xBaxNb2TiO12 and Ca5−xBaxTa2TiO12 were prepared by conventional solid-state ceramic route. The crystalline structures were determined by x-ray diffraction, which showed that solid solutions were formed for x=4 (CaBa4Nb2TiO12 and CaBa4Ta2TiO12) and crystalline multiphases appeared for 1⩽x⩽3. The dielectric properties of the sintered ceramics were measured in the microwave frequency range. The dielectric constant and temperature variation of resonant frequency increased and the quality factor decreased with increasing x value. Raman analyses showed different spectra depending upon the composition, with variations in both intensity and frequency, as well as in the number of bands strictly related to the phases present. For both Nb- and Ta-based systems, the results indicated an increase in the short-range ordering with barium substitution, which explained the reduction in the unloaded quality factor (Qu). The results of far-infrared spectroscopy agree well with the Raman data, with few variations when Nb replaces Ta, and an increase in the complexity of the vibrational modes for Ca∕Ba mixed ceramics.
Publisher: American Chemical Society (ACS)
Date: 30-06-2007
DOI: 10.1021/CM070894N
Publisher: American Chemical Society (ACS)
Date: 22-07-2008
DOI: 10.1021/CM800969M
Publisher: IOP Publishing
Date: 13-03-2009
Publisher: American Chemical Society (ACS)
Date: 10-06-2008
DOI: 10.1021/CM8003326
Publisher: American Chemical Society (ACS)
Date: 07-12-2004
DOI: 10.1021/CM048411S
Publisher: American Chemical Society (ACS)
Date: 08-12-2010
DOI: 10.1021/CM1027964
No related grants have been discovered for Anderson Dias.