Building a resonant cavity for the measurement of microwave dielectric permittivity of high loss materials

Rubinger, C. P. L.; Costa, L.C.

doi:10.1002/mop.22506

Cited by 56 publications

(60 citation statements)

References 14 publications

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“…To measure the complex permittivity of the material, e* ¼ e 0 Àie 00 , a cavity perturbation method was used [7], in a rectangular cavity, operating in the TE 1,0,11 mode, at about 5 GHz. In the centre of the cavity, where the electrical field is maximal, the sample is inserted, provoking the perturbation of the field.…”

Section: Methodsmentioning

confidence: 99%

Structural and optical properties on thulium-doped LHPG-grown Ta2O5 fibres

Macatrão¹,

Peres²,

Rubinger³

et al. 2009

Microelectronics Journal

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a b s t r a c tStructural, spectroscopic and dielectric properties of thulium-doped laser-heated pedestal Ta 2 O 5 as-grown fibres were studied. Undoped samples grow preferentially with a single crystalline monoclinic structure. The fibre with the lowest thulium content (0.1 at%) also shows predominantly a monoclinic phase and no intra-4f 12 Tm 3+ recombination was observed. For sample with the highest thulium amount (1.0 at%), the appearance of a dominant triclinic phase as well as intraionic optical activation was observed. The dependence of photoluminescence on excitation energy allows identification of different site locations of Tm 3+ ions in the lattice. The absence of recombination between the first and the ground-state multiplets as well as the temperature dependence of the observed transitions was justified by an efficient energy transfer between the Tm 3+ ions. Microwave dielectric properties were investigated using the small perturbation theory. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for thulium-doped Ta 2 O 5 samples it decreases to 18 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value.

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Section: Methodsmentioning

confidence: 99%

Structural and optical properties on thulium-doped LHPG-grown Ta2O5 fibres

Macatrão¹,

Peres²,

Rubinger³

et al. 2009

Microelectronics Journal

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“…According to the small perturbation theory, 16 a linear relationship exists between the frequency shift ⌬f caused by the insertion of a sample in the cavity and the real part of the complex permittivity of the material Ј. The same behavior is observed in the change in the inverse of the quality factor of the cavity, ⌬͑1 / Q͒, related to the imaginary part, Љ.…”

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confidence: 87%

“…16 In the center of the cavity, where the electrical field is maximal, the sample is inserted, provoking the perturbation of the field. As a consequence, the transmission of the cavity changes.…”

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confidence: 99%

Microwave dielectric permittivity and photoluminescence of Eu2O3 doped laser heated pedestal growth Ta2O5 fibers

Rubinger

Costa

Macatrao

et al. 2008

Applied Physics Letters

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We report the microwave dielectric properties and photoluminescence of undoped and europium oxide doped Ta 2 O 5 fibers, grown by laser heated pedestal growth technique. The effects of Eu 2 O 3 doping ͑1 -3 mol % ͒ on the structural, optical, and dielectric properties were investigated. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for Eu 2 O 3 doped Ta 2 O 5 samples it increases, reaching up to 36 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value. For this wide band gap oxide, Eu 3+ optical activation was achieved and the emission is observed up to room temperature. Thus, the transparency and high permittivity make this material promising for electronic devices and microwave applications. In recent years, the doping of wide band gap transparent oxides with lanthanide ions has been performed mainly with the purpose of tuning desirable optical properties for optical and electro-optical applications.1 The demand for materials with high luminescence efficiency provided by the intra-4f n transitions has been a driving force for the exploitation of the spectroscopic properties in several oxide hosts.2-4 Besides the interest in laser optical materials, 5 oxide systems have been also widely investigated due to its interesting dielectric properties for dynamic random access memories and tunable microwave device applications.6-9 For instance, it is well known that high dielectric constant materials allow a high degree of miniaturization of the components used in many wireless communication systems. 10 The claim for materials with high dielectric constant and low dielectric losses is one of the motivations of new material development.In this letter, we report on the structural, optical, and microwave dielectric properties of Eu doped Ta 2 O 5 grown by laser heated pedestal growth ͑LHPG͒ technique. The Ta 2 O 5 was grown as transparent cylindrical fibers with 1 mm of diameter and 50 mm of length and have been intentionally doped with Eu 2 O 3 from 0 ͑i.e., undoped͒ to 3 mol % of concentration. With an ϳ3.8 eV bandgap at room temperature ͑RT͒, 11 the tantalum pentoxide crystalline fiber is a suitable host for the incorporation of lanthanide ions. Undoped and 1 mol % doped was found to have a monoclinic crystalline structure, but increasing doping ͑between 2 and 3 mol %͒, the appearance of a triclinic phase is promoted.11 The achievement of optically activated Eu 3+ was observed for all the doped samples as shown by photoluminescence ͑PL͒ and photoexcitation luminescence data.11 Figure 1 shows the temperature dependent PL spectra for the Ta 2 O 5 :Eu ͑3 mol % ͒ fiber carried out with above band gap excitation ͑325 nm cw He-Cd laser and an excitation power density less than 0.6 W cm −2 ͒. The intra-4f 6 transitions of Eu 3+ in the oxide matrix also sensitize the crystalline phase transformation as observed from the presence of three11 Two of the lines ͑576.5 and 578 nm, measured at 14 K͒ correspond to Eu 3+ related centers in the mo...

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“…Resonant methods have much better accuracy and sensitivity than nonresonant methods [1,13,14]. They are generally applied to characterization of low-loss materials.…”

Section: Introductionmentioning

confidence: 99%

“…They are generally applied to characterization of low-loss materials. In a recent study, it has been shown that they are also applicable to high-loss materials provided that very small samples are prepared or higher volume cavities are constructed [13]. Though, a meticulous sample preparation is needed before measurements.…”

Section: Introductionmentioning

confidence: 99%

Permittivity Measurement of Thin Dielectric Materials From Reflection-Only Measurements Using One-Port Vector Network Analyzers

Hasar¹

2009

PIER

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Abstract-We have proposed a simple waveguide method for complex permittivity determination of dielectric materials which are not completely filling the entire sample holder. The method reconstructs the permittivity from measured reflection-only scattering parameters by a one-port vector network analyzer of two configurations of the sample holder. It not only eliminates the necessity of any knowledge of the location of the shifted sample inside its holder but also decreases measurement errors occurring with the presence of undesired air gaps, which seriously affect the measurement accuracy of transmissiononly measurements, present between the sample and holder walls. Furthermore, the reconstruction of permittivity can be realized by any one-port vector network analyzer, which is less expensive than their two-port counterparts. Therefore, the proposed method is cost-effective. We have analyzed the accuracy of the proposed method and noted a good compromise between the reference data and measured values of permittivities of low-loss polyvinyl-chloride and polytetrafluoro.ethylene samples (less than 8 percent for dielectric constant and less than 15 percent for loss tangent values).

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Building a resonant cavity for the measurement of microwave dielectric permittivity of high loss materials

Cited by 56 publications

References 14 publications

Structural and optical properties on thulium-doped LHPG-grown Ta2O5 fibres

Structural and optical properties on thulium-doped LHPG-grown Ta2O5 fibres

Microwave dielectric permittivity and photoluminescence of Eu2O3 doped laser heated pedestal growth Ta2O5 fibers

Permittivity Measurement of Thin Dielectric Materials From Reflection-Only Measurements Using One-Port Vector Network Analyzers

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