M. A. S. Silva

Universidade Federal do Ceará | UFC · Departamento de Física

In this article, the dielectric properties of a Li4Ti5O12 (LTO) ceramic at the radio frequency (RF) and microwave (MW) regions were evaluated. X-ray diffraction showed that LTO was obtained without the presence of spurious and/or secondary phases. Complex impedance spectroscopy (CIS) analysis was conducted, whereas an activation energy (Ea) of 0.88...

The present article evaluates the effect of the addition of TiO2 on the dielectric properties in the radiofrequency region of the YNbO4 ceramic matrix. X-ray diffraction (XRD) showed that the YNT (Y(Nb0.5Ti0.5)2O6) phase formed from the reaction between YNbO4 (YNO) and TiO2 in the investigated composites. Complex impedance spectroscopy (CIS) analys...

The present work shows the dielectric properties of (100-X)Ba2TiSi2O8-(X)TiO2 composites (X in wt%) at radio frequency (RF) region (< 300 MHz). X-ray diffraction and Rietveld's refinement showed the presence of Ba2(Ti7/9Si2/9)9O20 (BTSO) phase in the studied composites. To analyze the relationship between the electrical properties and the microstru...

This work studies the dielectric properties in the microwave region (MW) of the Ba2TiSi2O8 (BTS) ceramic with TiO2 additions and its applications as a dielectric resonator antenna (DRA). In this study, structural characterization through x-ray diffraction (XRD) is performed and the Rietveld refinement is used to confirm the phases formed. Analysis...

The effect of doping of Co²⁺ and Sn⁴⁺ in Ba0.5Sr0.5Fe12-2xO19 hexaferrite with different concentrations (x = 0.2, 0.4, 0.6, 0.8, and 1.0) was studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), complex impedance spectroscopy, and analyzed as a dielectric resonating antenna (DRA) at room temperature. The samples were produced and...

This work presents experimental and numerical investigations of the microwave dielectric properties of the ceramic matrix CaMoO4 (CMO) with the addition of 8, 12, and 20 wt% TiO2, obtained through the solid-state reaction method. X-ray diffraction and Rietveld’s refinement revealed no evidence of secondary phases, indicating no reaction between the...

This paper reviews the dielectric properties of Sr2TiSi2O8 (STS) ceramic in the radio frequency (RF) and microwave (MW) regions. X-ray diffraction (XRD) analysis is used to demonstrate that a small secondary phase of SrTiO3 is present in a synthesised STS ceramic. Complex impedance spectroscopy is performed, and the typical permittivity values of c...

A series of MCuSi4O10 (M = Ca²⁺, Sr²⁺ and Ba²⁺) electroceramics have been prepared by solid-state reaction and sintered at 1150 (CCSO (CaCuSi4O10)), 1100 (SCSO (SrCuSi4O10)), and 1150 °C (BCSO (BaCuSi4O10)). The structure and dielectric properties of the samples were studied by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), im...

Neste trabalho são apresentados a síntese, caracterização estrutural e o estudo das propriedades dielétricas na região de micro-ondas (MW) da matriz de silicato de bário titânio Ba2TiSi2O8 com adições em massa de óxido de titânio (TiO2). A reação do estado sólido foi utilizada para obtenção da matriz cerâmica Ba2TiSi2O8 (BTS), sendo que nesse proce...

Herein, we report a study on the suitability of the Sr3Mo1‐xWxO6 (0.1 ≤ × ≤ 0.9) solid‐solution system for radio frequency and microwave (MW) applications. The ceramic powders were synthetized via solid‐state reaction at 1423 K for 6 h. X‐ray diffraction and scanning electron microscopy were performed to confirm the double‐perovskite‐type structure...

This work presents the study of the dielectric properties in the microwave region (MW) of BaMoO4 ceramic and composites with CaTiO3 (CTO). The BaMoO4 matrix was synthesized by solid state reaction and characterized by X-ray diffraction. Ceramic composites were obtained by adding 20–80 mol% of CTO in the BaMoO4 matrix. The Silva-Fernandes-Sombra met...

Molybdates from A2Mo3O12 family have been widely investigated due to its low sintering temperature, low thermal expansion coefficient, and low dielectric loss. Fe2Mo3O12 (FMO) is an oxide from this family and widely used in the catalytic field. The aim of this work is to evaluate the influence of the Bi2O3–B2O3 as a sintering aid in the microstruct...

Ba5Li2W3O15 (BLWO) electroceramics with different amounts of lithium carbonate (10–15%) were synthesized using the solid-state route. Powder x-ray diffraction (PXRD) and Raman spectroscopy showed the presence of the BaWO4 (BWO) phase in the samples. The excess lithium in the BLWO matrices contributed to an increase in the BWO phase and improved the...

Eu³⁺ – Tb³⁺ co-doped Sr3MoO6 (SMO) phosphors have been synthesized by solid-state reaction. Powder X-ray diffraction (PXRD) and Scanning electron microscopy (SEM) were used for the characterization of the synthesized materials, and no significant structural changes have been observed. Photoluminescence (PL) was obtained under the 290 nm excitation...

Bismuth layer structured ferroelectric Bi3R2Ti3FeO15 with R = Bi (BFTO), Gd (BGFTO), and Nd (BNFTO) composition were synthesized by solid-state route, and their morphology and dielectric properties were investigated. The BGFTO and BNFTO samples, show a decrease in dielectric characteristics compared to BFTO. This can be explained by structural dist...

The original version of this article unfortunately contained a mistake. The Eqs. (11) and (12) in the paper [1] have been published with errors. The correct version of Eqs. 11 and 12 are below (Formula presented.). Note that the errors were only typographical, calculations and discussions in the article are unaffected, and the conclusions remain un...

The present work shows present the dielectric properties of YNO – CYNTO ceramic composites at Radio Frequency (RF) and Microwave (MW) regions. X-ray diffraction showed that the addition of CaTiO3 (CTO) on YNbO4 (YNO) caused the formation of the CaYTiNbO7 (CYNTO) phase. In the RF analysis, a typical universal dielectric response in the frequency of...

In the present work, an electroceramic of the perovskite family, BiCu3Ti3FeO12 (BCTFO), was synthesized by the solid-state reaction method. The structural study was performed by X-ray diffraction and Mössbauer and Raman spectroscopy. Electric and dielectric properties were analyzed by impedance spectroscopy and the Hakki-Coleman method. Due to the...

In this study, the Pb(Zr0.65Ti0.35)O3 (PZT) structure was produced by the solid state reaction method, and a new polarization geometry was used to obtain the radial and thickness modes in cylindrical samples with more efficiency. The polarization procedure was investigated by varying the temperature from 30°C to 80°C. The experimental excitation of...

In this work, investigations of the FeNbO4 ceramic matrix (FNO) and TiO2 additions were carried out in 0, 20, 40, 60, and 80% wt. proportions. The material was synthesized using the solid-state reaction method in an energy mill, and the phases were confirmed by X-ray diffraction and Rietveld refinement. The study of complex electrical impedance was...

This work presents the dielectric properties of YNbO4 (YNO)-TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of...

This study reports the dielectric and structural characterisation of composites formed by the mixture of a BiVO4 ceramic matrix with ZnO (25, 50, and 75 wt.%) obtained through a solid-state method procedure for applications in the microwave range. X-ray diffraction is used for structural characterisation. The dielectric properties and temperature c...

It was produced a series of cylindrical dielectric resonator antennas (DRA) from the ceramic material LFO(1-x)CTO(x) (LFO = LaFeO3 ; CTO = CaTiO3 ; x = 0, 0.17, 0.31, 0.43, 0.54, 0.64, 0.68, 0.73 and 1 in molar fraction of CTO) to operate in the microwave region. This material was obtained by solid state reaction and characterized in an orthorhombi...

In this work, the electrical properties of Bi4Ti3O12 (BiT) were investigated; those presenting interesting electrical and dielectric properties in the radiofrequency (RF) and microwave (MW) range were analysed. BiT has many applications in telecommunication systems and MW circuits. It was synthesized by the solid-state reaction method, and X-ray di...

Magneto-dielectric composites are interesting advanced materials principally due to their potential applications in electronic fields, such as in microstrip antennas substrates. In this work, we developed superparamagnetic polymer-based films using the biopolymeric matrices chitosan (Ch), cellulose (BC) and collagen (Col). For this proposal, we syn...

Bismuth layer-structured ferroelectric Bi3R2Ti3FeO15 (R = Bi, Nd, and Gd) ceramics were synthesized by conventional solid-state reaction. All the samples showed an orthorhombic structure with A21am space group. Bi3Nd2Ti3FeO15 and Bi3Gd2Ti3FeO15 presented a reduction in the orthorhombicity when compared to Bi5Ti3FeO15. The magnetic susceptibility of...

In this work, a complex impedance spectroscopy study of bismuth vanadate (BiVO4) ceramics with different additions of ZnO (25, 50, and 75 wt %) was performed. BiVO4 (BVO) was synthesized by the reaction method in solid-state and calcined at 500 °C and BVO–ZnO composites were moulded in sintered ceramic pellets at 700 °C. X-ray diffraction (XRD) was...

Bismuth layer-structured ferroelectric Bi3R2Ti3FeO15 (R = Bi, Nd, and Gd) ceramics were synthesized by conventional solid-state reaction. All the samples showed an orthorhombic structure with A21am space group. Bi3Nd2Ti3FeO15 and Bi3Gd2Ti3FeO15 presented a reduction in the orthorhombicity when compared to Bi5Ti3FeO15. The magnetic susceptibility of...

This paper analysed the effects of doping with Pr and Yb on the dielectric and down-conversion luminescence properties in the ceramic matrix LaNbO4. X-ray diffraction analysis showed that no additional phases were present in the materials. Impedance spectroscopy analysis demonstrated increasing conductivity due to the generation of oxygen vacancy,...

Molybdates from A 2 Mo 3 O 12 family have been widely investigated due to its low sintering temperature, low thermal expansion coefficient, and low dielectric loss. Fe 2 Mo 3 O 12 (FMO) is an oxide from this family and widely used in the catalytic field. The aim of this work is to evaluate the influence of the Bi 2 O 3 -B 2 O 3 as a sintering aid i...

This study presents the novel (LaFeO3)(1-m)(CaTiO3)m (m = 0, 0.1, 0.3 and 0.5 in weight fraction) solid solutions. These materials were obtained by conventional solid-state reaction between LaFeO3 (LFO) and CaTiO3 (CTO) perovskite phases despite the favorable conditions for the composite formation. The X-Ray diffraction (XRD) confirmed the solid so...

This work shows a planar interdigital sensor for rapid measurement of oils. The kit is characterised by the impedance meter, a Raspberry Pi3 and a sample port where the planar capacitive interdigital multifinger (IDCM) sensor is stored. For validation of this IDCM sensor, the data was compared with measurements performed by impedance spectroscopy (...

In this work, the investigation of Sr2CoNbO6–TiO2 composite, which shows interesting dielectric characteristics (low loss and high dielectric permittivity), was carried out. The Sr2CoNbO6(SCNO) system is widely applied in electro-electronic devices due to their dielectric characteristics. SCNO was synthesised via solid state reaction, and x-ray dif...

The present work shows the electric and dielectric study of ceramic composites made from cobalt titanate CoTiO3 (CoTO) and vanadium oxide (V2O5), by complex impedance spectroscopy. The CoTO was obtained by solid state reaction, the structural properties of the CoTO and the composites were discussed using X-ray diffraction and the electric and diele...

This work presents the dielectric properties of several oxides used as sintering aids for the manufacture of thermally stable ceramics in the radio frequency (RF) and microwave ranges. The oxides were prepared in pallets and cylinder geometries, with sintering close to their melting point for 4 h. The dielectric properties in the RF range were anal...

This paper investigated the microwave dielectric properties through the Hakki-Coleman method of BiVO4 ceramic matrix, obtained by the solid-state reaction method, using 8, 16, 24 and 32 wt% of CaTiO3. The X-ray diffraction (XRD) was used for the structural characterisation of the crystalline phases present in ceramic before the sinterisation proces...

In this work, composites based on the ceramic matrix Ba 2 CoNbO 6 (BCNO) 1-X - CaTiO 3 (CTO) X were fabricated using the solid-state reaction method. X-ray diffraction and scanning electron microscopy were used for structural and morphological characterization of the material. The dielectric properties of the composites in the microwave and radio f...

in the microwave range by measuring their di-electric properties comprising the temperature coefficient of the resonant frequency (τ f), relative dielectric permittivity (ε r), and dielectric loss (tanδ) in the C band (4-8 GHz). The Li 2 TiO 3 phase was obtained by solid-state reaction and the ceramic composites were obtained by blending phase 2 wi...

Yttrium iron garnet and calcium titanate (Y3Fe5O12-CaTiO3, YIG-CTO) ceramic composite were obtained according to the well-established solid-state route. This system was studied by complex impedance spectroscopy as a function of temperature. All samples showed a thermo-activated relaxation with energy activation between 1.10 and 1.70 eV. The CaTi0.6...

In this work, we have analysed the effects of adding CaTiO3 (CTO) and changing the temperature on the dielectric and electric properties of ceramic matrix BiVO4 (BVO) in the radiofrequency range. BVO was synthesized by a calcination process at 500 °C and ceramic composites were prepared by the addition of CTO (8, 16, 24, 28 and 32 wt%). These compo...

This paper reported the dielectric and structural characterization of composites formed by mixture of BiVO4 and TiO2 and applications in microwave range. The composites were formulated by addition of TiO2 (15, 30, 45 and 60 wt %) in BiVO4. X-Ray Diffraction (XRD) was used in structural characterization. The dielectric properties, temperature coeffi...

This paper presents the application of the Li2MgTi3O8 (LMT) ceramic matrix added with small quantities (0 wt.%, 1 wt.%, 3 wt.%, and 5 wt.%) of Bi2O3 for building and studying dielectric resonator antennas (DRA) to operate in microwave frequency bands. A low-cost procedure of manufacturing was applied to produce a material with good dielectric chara...

In this work, the dielectric and electric properties of the ceramic matrix BiVO4 (BVO) and the effects of the addition of TiO2 were analysed by impedance spectroscopy (IS). The BVO phase was calcined at 773 K and used to prepare the composite ceramic which the titanium oxide was added (15, 30 and 60 wt% TiO2), molded in pellet shape and sintered at...

In this work, we prepared ceramic composites based on SrFe12O19 (SFO)-BiFeO3 (BFO) strontium hexaferrite. The SFO and BFO were synthesized by the solid-state reaction method, and we used both x-ray diffraction and infrared spectroscopy for structural characterization of the composite matrix. The electrical and dielectric properties were measured in...

This work aims to develop an eco-friendly ceramic obtained from the sludge generated in the textile industry treatment by electrocoagulation to demonstrate a possibility of natural raw materials’ extraction decrease. The sludge generated by the electrocoagulation treatment was treated by some sintering processes. The presence of two crystalline pha...

LiFe5O8 (LFO) spinel-like material has been studied for use in ferrite resonator antennas (FRAs). Antenna parameters such as gain and return loss were greatly affected when an external magnetic field was applied to the FRA. The temperature coefficient of the resonant frequency (τf ) for the FRA presented a value of − 482.16 ppm/°C. The magnetic hys...

The Sr3MoO6 (SMO) double perovskite has been studied due to its photoluminescence properties. Herein, the aim of this work is to study the dielectric properties of the SMO in radiofrequency (RF). From impedance spectra, we proposed an equivalent circuit using three associations of R-CPE in parallel. We also evaluated its performance as a microwave...

The effects of different BiFeO3 (BFO) additions (0, 20, 40, 60 and 80 wt%) on the SrFe12O19 hexaferrite ceramic matrix (SFO) have been studied by Complex Impedance Spectroscopy (CIS), Mössbauer spectroscopy, magnetic hysteresis and X-Ray Diffraction (XRD) analysis. The solid state reaction method was used for the production of the SFO and BFO, the...

In this work, we present a dielectric study on the Sr3V2O8 (SVO) ceramic matrix in the radiofrequency spectrum by using Impedance Spectroscopy (IS). We calcined pure phase SVO through the conventional solid-state reaction at 950◦C and sintered the ceramic pellet at 1050◦C. In the analyzed by X-ray Diffraction, the SVO presented single phase. At the...

In this work, we fabricated ceramic composites based on the composite matrix Sr2CoNbO6 (SCNO)-TiO2. The SCNO was synthesized by solid-state reaction, and x-ray diffraction was used for the structural characterization of this synthesis. We measured the dielectric properties in the microwave range by using the Hakki–Coleman method, as well as the the...

On this paper, polycrystalline samples of the tetragonal systems BaBi2Nb2O9 (BBN) and BBN co-doped with Er3+/Yb3+ (BBN: 0.04Er(3+)yYb(3+), where y=0.02, 0.04, 0.06 and 0.08 mol%) were synthesized by the solid state method. The crystalline structure and photoluminescent properties of the ceramic phosphors were investigated by powder X-ray diffractio...

A new planar triple band microstrip-fed Planar Inverted-F Antenna (PIFA) for the use in GSM835 band (698–989 MHz), DCS1940 band (1824–2033 MHz) and Wi-Fi2340 band (2302–2548 MHz) is reported. A numerical study based on the parameters like ground plane length, height of radiating plate, feeding point position, shorting plate width, and position, was...

The nature and symmetry of transition mechanisms in the spin-spiral copper halides CuCl2 and CuBr2 are analyzed theoretically. The magnetoelectric effects observed in the two multiferroic compounds are described and their phase diagram at zero and applied magnetic fields are worked out. The emergence of the electric polarization at zero field below...

Lanthanum ortho-niobate matrices, LaNbO4 (LNO), doped with rare-earth ions (Er³⁺ and Yb³⁺), were prepared by a high-temperature solid-state reaction method. The LNO matrices thus prepared were confirmed by X-ray diffraction followed by Rietveld refinement. Raman spectroscopy was used to analyze the vibrational energy of the undoped and rare-earth d...

This work presents results of a study of the alumina-niobium oxide composite (Al2O3)-(Nb2O5) dielectric properties in the radio frequency and microwave range. The characterization study was performed in a matrix of alumina by varying the amount of niobium oxide (2.5%–10% by weight. amount). The samples were sintherized at the temperature of 1350°C....

Multiferroic materials are intensively investigated as potential candidates for a new generation of solar cells, due to the coexistence in their phases of ferroelectricity and magnetic order with low band gap. However, symmetry considerations, which determine the interplay between the magnetoelectric and photovoltaic properties of a light irradiate...

This work reports the dielectric properties of Sr3WO6 (SWO) double perovskite at radio frequencies as a function of the temperature and a study in microwaves range to evaluate the material as a novel dielectric resonator. Thermo-activated charge transfer process for SWO ceramic was observed and two resistor–capacitor associations were fitted for th...

In this paper is reported an experimental and numerical investigation of the microwave dielectric properties of Na2Nb4O11 (NN), ceramic matrix added with (0, 2, 5, and 10 wt%) of Bi2O3, obtained through a new procedure based on the solid-state method. The experimental and theoretical characteristics of the resonator like return loss, bandwidth, inp...

The nature and symmetry of the transition mechanisms in the spin-spiral copper halides CuCl$_2$ and CuBr$_2$ are analyzed theoretically. The magnetoelectric effects observed in the two multiferroic compounds are described and their phase diagram at zero and applied magnetic fields are worked out. The emergence of the electric polarization at zero f...

Abstract This work investigates the microstructure and magnetic–dielectric properties of the CaTiO3 (CTO) and Y3Fe5O12 (YIG) composite ceramic. CTO is a paramagnetic ceramic, presents a positive value of Resonant Frequency Temperature Coefficients (τf) and has high dielectric permittivity (εr) while YIG is ferromagnetic, has low εr and negative τf...

We have studied the effect of addition of titania, as a sintering agent, to alumina on the dielectric characteristics of the ceramic composites obtained. The dielectric properties of the titania–alumina composites were studied by use of impedance spectroscopy and the Hakki–Coleman method in the radio-frequency and microwave regions, respectively. T...

Muitas pesquisas têm sido realizadas buscando materiais que apresentem excelentes propriedades dielétricas. Dentre esses materiais destaca-se o niobato de lantânio, já que este material possui propriedades interessantes. O objetivo deste trabalho é realizar a caracterização estrutural e dielétrica da cerâmica LaNbO 4 (LNO) pura e com adição de 1% d...

Neste trabalho foi feito o estudo de antenas resssoadoras dielétricas (DRA) da matriz cerâmica FeNbTiO 6 (FNTO). As amostras analisadas foram adicionadas com ZnO e seguiram as seguintes proporções 0%, 8% e 25%. As propriedades dielétricas de microondas demonstraram variação significativa para a permissividade (47,23-63,77) e aumento das perdas diel...

Este trabalho visa estudar as propriedades dielétricas do FeNbTiO 6 (FNTO) nas regiões de micro-ondas e rádio frequência. A cerâmica de FNTO foi preparada por reação em estado sólido a 1075°C e adicionado com ZnO. O estudo foi realizado por difração de raios-X. As propriedades dielétricas das amostras foram medidas por Espectroscopia de Impedância...

In this article is present the structural and dielectric microwave properties of Alumina – CaTiO3 ceramic composite with the addition of CaTiO3 and your performance as a dielectric resonator antenna (DRA). Alumina has a negative temperature variation of resonant frequency coefficient τf, while CaTiO3 has a high positive temperature coefficient. Als...

This article proposes a dielectric resonator in the form of a quarter of a cylinder to perform as a circularly polarized antenna using a very simple feed design on which a single probe excites two resonant modes in phase quadrature and spatial orthogonality. This study examines some electromagnetic aspects of this antenna and it also presents and d...

In this study, magnetic nanobiocomposites were prepared in different proportions and produced with galactomannan (GM), magnetic nanoparticles of NiZn and glycerol (GL). The microstructure and morphology of the samples were characterized by Scanning Electron Microscopy (SEM), X-ray powder diffraction, Fourier transform infrared (FTIR) spectroscopy,...

In this work we analyze the XRD of two thin films samples, one of CdS (Space group: P63mc) and another of SnO2 (Space Group: P42/mnm) grown on a glass substract. The CdS thin film, growth via CBD (Chemical Bath Deposition), and the difficulties found for a clear peak around 2(theta)=31.2 growth in the direction [111] of the cubic structure, accordi...

Muitas pesquisas têm sido realizadas buscando materiais que apresentem excelentes propriedades dielétricas. Dentre esses materiais destaca-se o LaNbO 4 , já que este material possui propriedades interessantes nas mais diversas áreas como opticoeletrônica; dipositivos eletrônicos; etc. O objetivo deste trabalho foi realizar a caracterização estrutur...

Com o desenvolvimento da tecnologia sem fio, muitos dispositivos eletrônicos exigem alta integração e que possuam propriedades multifuncionais. Em tal caso, compósitos magneto-dielétricos têm atraído muita atenção, porque eles têm tanto propriedades dielétricas como magnéticas. O titanato de cálcio e a granada de ítrio e ferro possuem excelentes pr...

The main object of this work is to study two materials with giant dielectric constants: CaCu3Ti4O12 (CCTO) and Ca0.7Bi0.3Ti0.7Cr0.3O3 (CBTC). CBTC1−x –CCTO x composites were also obtained to create a new dielectric material with dielectric properties between these two phases. Structural properties were studied by x-ray powder diffraction (XRPD), Fo...

A partir dos óxidos em pó, Fe 2 O 3 (Sigma-Aldrich, 99,0%), Nb 2 O 5 (Sigma-Aldrich, 99,99%) e TiO 2 (Vetec, 99,75%), foi feita a síntese, através método de reação em estado sólido da cerâmica Ti 0.4 Fe 0.3 Nb 0.3 O 2 (TFNO). Seguindo as proporções estequiométricas os óxidos foram misturados e moídos por 7h e calcinados por 4h a 1075°C. Por meio da...

O SrBi 4 Ti 4 O 15 (SBTi) é uma típica perovskite com deficiência de cátions. Este trabalho tem como objetivo estudar as propriedades dielétricas e elétrica de do material SBTi dopado de óxido de vanádio (V 2 O 5). O SBTi foi preparado pelo método cerâmico. Os pós de oxido de Bismuto (Bi 2 O 3), Óxido de Titânio (TiO 2) e Carbonato de Estrôncio (Sr...

In this paper is reported an experimental and numerical investigation of the microwave dielectric properties of BiFeO3 (BFO) ceramic matrix added with 3 and 10 wt% of Bi2O3 or PbO, obtained through a new procedure based on the solid-state method. The experimental and theoretical characteristics of the resonator like return loss, bandwidth, input im...

In this paper SrBi4Ti4O15 (SBTi), a perovskite-type ceramic, with cation deficit A5B4O15, was prepared by solid-state reaction method and PbO and V2O5 were added into SBTi (2, 5, 10 and 15 wt%). Samples were characterized through X-Ray Diffraction (XRD), Raman Spectroscopy and Scanning Electron Microscopy (SEM). Impedance Spectroscopy was carried o...

In this work, BBT has been synthesized by solid-state reaction. X-ray diffraction and Raman spectroscopy were used to structurally characterize the samples. The dielectric properties were analyzed by impedance spectroscopy for radiofrequency range. For microwave range, the dielectric properties were analyzed by the Hakki–Coleman method. The propert...

In this paper an alternative method for the measurement of the temperature coefficient of resonant frequency (τf), is presented. The traditional method (based on the Courtney method) present some limitations of measuring the values of τf, for samples with high dielectric loss due to their inability to observe clearly the TE011 mode. The alternative...

This paper presents the microwave dielectric properties and a structural study of SrBi2Nb2O9 (SBN) added La2O3, PbO or Bi2O3 obtained by a solid state procedure. High-energy mechanical milling was used to reduce the particle size, which allows for a better shaping of the green body and an increased reactivity. The mechanical milling activation proc...

RESUMO Este estudo objetiva sintetizar e caracterizar a cerâmica BBT (BaBi 4 TI 4 O 15) dopada com 1% em massa de Nb 2 O 5 para melhorar a densificação dos produtos. A fase do BBT foi encontrada por reação de estado sólido. Os óxidos de partida misturados sofreram moagem de alta energia em moinho planetário com reatores poliméricos e esferas de zir...

RESUMO O estudo da síntese e caracterização estrutural da cerâmica BiNbO 4 e o comportamento da densidade quando adicionado 10% de CuO em massa, com vistas a aplicação em capacitores cerâmicos, são apresentados neste trabalho. O BiNbO 4 foi preparado pelo método convencional cerâmico. Os pós moídos por 2h foram calcinados a 850°C por 3h e caracteri...

In this work, we study for the first time the dielectric properties, at microwave frequencies, of the BiREWO6 (RE = Y, Gd, and Nd) dielectric resonator (DR) obtained by microwave assisted fast solid state synthesis. The DRs were excited by a wire antenna protruding above a ground plane and simulations were carried out using high-frequency structure...

We report a study of the structural and thermal characteristics of calcium titanate alloys Ca[(Li1/3Nb2/3)xTi1−x]O3−δ (abbreviated as CNLTO). CNLTO alloys were prepared using a new procedure in the solid-state reaction method. Then they were studied using x-ray diffraction, Raman scattering spectroscopy and microwave properties. The symmetry of the...

This paper presents a study of the structure and microwave properties of ${\rm Nb}_{1/2}^{5+}{\rm Fe}_{1/2}^{3+}$ substituted into the Ti⁴⁺ site of calcium titanate ceramics. The structural and dielectric properties of solid solutions in CaTi1-x(Nb1/2Fe1/2)xO3, was done. The microwave dielectric properties of solid solutions in CaTi1-x(Nb1/2Fe1/2)x...

In this work, we study the dielectric properties and structure of the BiYWO6 dielectric resonator (DR) obtained by microwave assisted fast solid state synthesis. The crystal structure of BiREWO6 (RE=rare earth) can be associated to the Bi2WO6 perovskite structure. It was observed that the crystalline structure was attributed to a monoclinic phase w...