Dielectric spectroscopy of LiNbO3 and TmNbO4 nanocrystals embedded in a SiO2 glass matrix

Silva, C.C.; Sombra, A. S. B.; Graça, M.P.F.

doi:10.1016/j.jnoncrysol.2009.09.044

Cited by 5 publications

(3 citation statements)

References 27 publications

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“…These results suggest that the development of a unit cell distorted structure, which is the case of the formation of polymorphic H-Nb 2 O 5 (Figure ), facilitates the formation of a microstructure with grains oriented in a preferred direction. Thus, the presence of a preferential orientation promotes an increase of the dipole moment, experimentally observed by the increase of the dielectric constant value. The presence of the B-Nb 2 O 5 monoclinic phase in the sample NbO-80K treated at 900 °C, does not influence significantly the dielectric results due, probably, to its low content.…”

Section: Resultsmentioning

confidence: 89%

Sintered NbO Powders for Electronic Device Applications

et al. 2011

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Wide band gap niobium oxides are particularly important for electronic device applications. Two types of NbO powders were sintered between 300 and 1100 °C. The structural characterization of the pellets, performed by X-ray diffraction measurements and Raman spectroscopy, revealed the appearance of the NbO and T-, B-, and H-Nb2O5 polymorphs, depending on the sintering temperature. The optical characterization was complemented with absorption measurements and photoluminescence, where it was possible to identify a bandgap of 3.5 eV. A strong dependence of luminescence on the sintering temperature and therefore of the niobium oxide crystalline phases nature was observed. The influence of the morphological and structural characteristics on the dielectrical properties, at room temperature and in the low frequency range (<100 MHz), was studied. The sample with the H-Nb2O5 polymorph presents higher dielectric constant (∼55) than the samples with T- and B-Nb2O5 (∼25).

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Section: Resultsmentioning

confidence: 89%

Sintered NbO Powders for Electronic Device Applications

et al. 2011

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“…Many LN glass-related studies have been concerned with the addition of glass network forming oxides such as borate, 22,23 silicate, [24][25][26][27] germinate 28 and alumina. 29 However, in most of these studies the opto-electrical properties of LN glass-related samples rather than the kinetics and mechanism of the corresponding samples have been discussed.…”

Section: Introductionmentioning

confidence: 99%

Crystallization kinetics of lithium niobate glass: determination of the Johnson–Mehl–Avrami–Kolmogorov parameters

Choi

Kim

Rim

et al. 2013

Phys. Chem. Chem. Phys.

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The formation of crystalline LiNbO3 (LN) from LN glass has been studied by means of differential scanning calorimetry and in situ synchrotron X-ray diffraction. The LN glass with no glass former was prepared by the polymerized complex method. The isothermal kinetics of the crystallization process is described using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and the Avrami exponent n is found to be ~2.0, indicating that the crystallization mechanism is diffusion-controlled growth with a decreasing nucleation rate. The effective activation energy of crystallization calculated from isothermal measurements is 6.51 eV. It is found that the LN glass directly transforms into a rhombohedral LN crystal without any intermediate crystalline phase and most crystal grains are confined within the size of ~40 nm irrespective of different isothermal temperatures. Application of JMAK theory to the non-isothermal thermoanalytical study of crystallization of LN glass is discussed.

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“…There are many examples in the literature of the combined use of impedance spectroscopy and electron microscopy to derive information of microstructural relevance that is not accessible using one of the techniques alone 9 . This approach has been applied with great success to characterize heterogeneous glasses prepared by the crystallization of homogenous glasses, and consisting of a distribution of a large number of fine crystallites of various phases embedded in a glassy matrix 11–16 . The dielectric behavior of a heterogeneous glass material depends on the contributions from different polarization processes present at crystalline phases, glassy matrix, the glass–crystal interface region, and the sample–electrode interface.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Properties of Reduced Heterogeneous Silica–Titania Glasses

Medina

Furman

Lanagan

2010

Int J of Appl Glass Sci

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We have studied the frequency and temperature dependences of the dielectric properties of a heterogeneous silica-titania (SiO 2 -TiO 2 ) glass by ac impedance spectroscopy measurements in the temperature range 25-7001C and the frequency range 40-10 7 Hz. The heterogeneous glass was prepared by the controlled heat treatment of a homogenous SiO 2 -TiO 2 glass, containing B7.5 wt% TiO 2 , in a reducing atmosphere to create a microstructure consisting of many discrete particles of the rutile/ anatase TiO 2 phase dispersed in a homogeneous SiO 2 -rich glassy matrix. Unlike the homogeneous SiO 2 -TiO 2 glass, which exhibited only one electrical/dielectric dispersion, presumably due to ion hopping, the heterogeneous glass material exhibited two distinct electrical responses in the impedance formalism. We attributed these contributions to the two-phase microstructure and explained the dielectric behavior in terms of the Maxwell-Wagner relaxation arising at the interfaces between the TiO 2 crystals and the SiO 2 -rich matrix phase.

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Dielectric spectroscopy of LiNbO3 and TmNbO4 nanocrystals embedded in a SiO2 glass matrix

Cited by 5 publications

References 27 publications

Sintered NbO Powders for Electronic Device Applications

Sintered NbO Powders for Electronic Device Applications

Crystallization kinetics of lithium niobate glass: determination of the Johnson–Mehl–Avrami–Kolmogorov parameters

Dielectric Properties of Reduced Heterogeneous Silica–Titania Glasses

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