Properties In Microwave Range Research Articles

Detection of an emerging contaminant in water by dielectric properties in microwave range

The complex relative permittivity study of samples of liberdux® syrup dissolved in distilled–deionized water is presented. It should be mentioned that excess of this syrup as pharmaceutical residual in water is considered an emerging contaminant. The study covers liberdux® concentrations from 0% v/v to 100% v/v, which were measured from 500 MHz to 20 GHz. For each sample, the parameters of the Havriliak–Negami model are presented in the range of measurement. Also, the uncertainty study was carried out to determine the sensitivity of the open coaxial probe and it was established that, for concentrations between 8% v/v and 100% v/v, it is possible to determine the concentration of liberdux® in water by the dielectric constant and the loss factor. In addition, a linear relationship was found between the concentration of liberdux® and the α parameter of the Havriliak–Negami model. The study of liberdux® concentrations was also performed with a spectrophotometer and the Beer–Lambert equation. It was established that the spectrophotometer and the open coaxial probe can be used as complements to measure concentrations, the spectrophotometer being the instrument for measuring low concentrations by absorbance, and the open coaxial probe for high concentrations by microwave permittivity.

The microwave dielectric properties of CaxSr1−xBi2Nb2O9 (0.0 ≤ x ≤ 1.0) ceramics

To improve the microwave dielectric properties of SrBi2Nb2O9 ceramics, the Ca element was selected as the substitute for Sr site. The CaxSr1−xBi2Nb2O9 ceramics were prepared by the conventional solid-state ceramic route. The crystal structure, microstructural evolution and microwave dielectric properties of CaxSr1−xBi2Nb2O9 (x = 0.0, 0.3, 0.6 and 1.0) were investigated. With the content of Ca2+ ions increasing, the dielectric constant er decreased from 145 to 98 and Q × f value increased from 167 to 672 GHz, respectively. Increasing sintering temperature can effectively promote the dielectric properties of CaxSr1−xBi2Nb2O9 ceramics. The optimal microwave dielectric property of er = 98, Q × f = 672 GHz was obtained for the CaBi2Nb2O9 ceramic sintered at 1050 °C for 5 h. The relatively low sintering temperature and high dielectric properties in microwave range would make CaxSr1−xBi2Nb2O9 ceramics promising for application in electronics.

The microwave dielectric properties of CaxBi4−xTi3O12−x/2 (0.0 ≤ x ≤ 1.4) ceramics

In this work CaxBi4−xTi3O12−x/2 ceramics were prepared by the conventional solid-state ceramic route. Densification, microstructural evolution and microwave dielectric properties of CaxBi4−xTi3O12−x/2 (x = 0.0, 0.6, 1.0, 1.2 and 1.4) were investigated. The room temperature structural data were obtained from X-ray diffraction (XRD). For x = 1.4, little secondary phases was observed. Therefore, the solubility limit of CaxBi4−xTi3O12−x/2 ceramics was estimated to x = 1.2. The microstructure and microwave dielectric properties were investigated as a function of the x-value and sintering temperature. Increasing sintering temperature can effectively promote the densification and dielectric properties of CaxBi4−xTi3O12−x/2 ceramics. With the content of Ca2+ ions increasing, the dielectric constant er and Q × f values increased at the beginning and then decreased. The optimal microwave dielectric property of er = 166, Q × f = 704 GHz was obtained for the Ca1.2Bi2.8Ti3O11.4 ceramic sintered at 1050 °C for 5 h. The relatively low sintering temperature and high dielectric properties in microwave range would make CaxBi4−xTi3O12−x/2 ceramics promising for application in electronics.

Effects of B2O3 addition on sintering behavior and microwave dielectric properties of ixiolite-structure ZnTiNb2O8 ceramics

The effects of B2O3 additives on the sintering behavior, microstructure and microwave dielectric properties of ixiolite-structure ZnTiNb2O8 ceramics prepared by conventional solid-state route were investigated. The B2O3 additives, acting as a sintering aid, can effectively decrease the sintering temperature of ZnTiNb2O8 ceramics to 1050 °C, due to the formation of liquid phase. Little second phase from XRD results was observed throughout the entire experiments. The variations in the dielectric constant (εr) and quality factor (Q·f) of the ixiolite-structure ZnTiNb2O8 ceramics were studied systematically depending on the adopting of B2O3 and the sintering temperatures. With the increase of the B2O3 addition, εr and Q·f decreased and the temperature coefficient of resonant frequency (τf) slightly fluctuated around −20 ppm/°C. The optimal microwave dielectric properties with high εr ∼35.04, Q·f ∼50,100 GHz, and a near-zero τf ∼−20.21 ppm/°C were obtained at 1 wt%-B2O3-doped samples sintered at 1050 °C. The relatively low sintering temperature and high dielectric properties in microwave range would make ZnTiNb2O8 ceramics promising for application in electronics.

Effect of H3BO3 addition on the sintering behavior and microwave dielectric properties of wolframite-type MgZrNb2O8 ceramics

The effect of H3BO3 addition on sintering behavior, microstructure and microwave dielectric properties of MgZrNb2O8 ceramics was investigated by solid-state method. With H3BO3 addition, the densification of MgZrNb2O8 ceramics was improved significantly, and the τf was adjusted to shift toward zero direction. Due to the effect of liquid phase produced from H3BO3 addition, the sintering temperature was lowered effectively. The variations in the dielectric constant (εr) and the Q·f values of the MgZrNb2O8 ceramics are depended on the amount of H3BO3 doping and the sintering temperature. As a result, an optimal microwave dielectric property of Q·f = 58,930 GHz, εr = 23.72, and τf = −13.19 ppm/°C was obtained for the MgZrNb2O8 ceramic with 1 wt% H3BO3 addition sintered at 1200 °C for 4 h. The relatively low sintering temperature and high dielectric properties in microwave range would make MgZrNb2O8 ceramics promising for application in electronics.

Microstructure and microwave dielectric characteristics of the CaxZn1−xTiNb2O8 temperature stable ceramics

The quantitative determination and the crystal structure of CaxZn1−xTiNb2O8 ceramics were analyzed by X-ray diffraction, the microwave dielectric properties were investigated. The results showed that the CaxZn1−xTiNb2O8 ceramics contained three main phases: ZnTiNb2O8 phase Zn0.17Nb0.33Ti0.5O2 phase and CaNb2O6 phase. With the increase of Ca content, the weight fraction of secondary phase Zn0.17Nb0.33Ti0.5O2 and CaNb2O6 increased. For ZnTiNb2O8, with the substitution of Ca2+ for Zn2+, the bond valence of Ti-site increased. The variation of distortion of oxygen octahedral was irregular. For Zn0.17Nb0.33Ti0.5O2, the distortion of oxygen octahedral and the bond valence of Ti-site increased with substitution of Ca2+. The increase of Ti-site bond valence led to a harder rattling of Ti cations of the specimens. As a result, the dielectric constant (e) and the quality factor value (Qf) decreased, the temperature coefficient of resonant frequency (τf) moved to the positive direction. The typical values of e = 38.6, Qf = 41,338 GHz, τf = −1.28 × 10−6/°C were obtained for CaxZn1−xTiNb2O8 (x = 0.45) specimens sintered at 1100 °C for 6 h. The high dielectric properties in microwave range drive these materials a promising application in electronics.

Synthesis, characterization, and microwave dielectric properties of ixiolite-structure ZnTiNb2O8 ceramics through the aqueous sol–gel process

Microwave dielectric ceramics based on ixiolite-structure ZnTiNb2O8 were prepared by an aqueous sol–gel process.Highly reactive nanosized ZnTiNb2O8 powders with particle sizes of 30–50nm were successfully obtained at 700°C as precursors. Sintering characteristics and microwave dielectric properties of ZnTiNb2O8 ceramics were studied depending on sintering temperatures ranging from 950°C to 1100°C. The dielectric properties were strongly dependent on the compositions, the densifications and the microstructures of the specimens. With the increase of sintering temperature, density, εr and Q⋅f values were increased and saturated at 1050°C with excellent microwave properties with an εr of 35.3, an high Q⋅f of 66,700GHz, and a τf of −55.4ppm/°C. The correlations of microstructure and dielectric properties for ZnTiNb2O8 ceramics were also investigated. The relatively low sintering temperature and high dielectric properties in microwave range would make these ceramics promising for application in electronics.

A temperature stable microwave dielectric material Ni0.35Zn0.65TiNb2O8

A temperature stable, high quality, low sintering temperature microwave dielectric material Ni0.35Zn0.65TiNb2O8 was investigated for the first time. The compounds were prepared by a conventional mixed-oxide route and sintered at the temperature range of 1,060–1,140 °C. The microstructure and microwave dielectric properties were investigated systematically. The X-ray diffraction results show that the Ni0.35Zn0.65TiNb2O8 ceramics contained two phase: ZnTiNb2O8 phase and Zn0.17Nb0.33Ti0.5O2 phase. With increase in temperature, the amount of ZnTiNb2O8 phase decreased and that of Zn0.17Nb0.33Ti0.5O2 increased. The microwave dielectric properties of Ni0.35Zn0.65TiNb2O8 were mainly affected by the variation of content and crystal structure of each phase. With increasing temperature, the content of Zn0.17Nb0.33Ti0.5O2 phase increased, resulting in the increasing dielectric constant and τ f , and decreasing Qf value. In addition, the dielectric constant increased with increasing bulk density, the Qf value were related to the cell volume of each phase, and the τ f value had correlation with the bond valence of each phase. Outstanding microwave dielectric properties of e = 40.9, Qf = 40,870 GHz, especially near-zero τ f = 0.62 × 10−6/°C were obtained sintered at 1,100 °C for 6 h. With the relatively low sintering temperature and excellent dielectric properties in microwave range, this material is very promising for electronic devices application.

Structure analysis and microwave dielectric properties of CaxZn1−xSn0.08Ti1.92Nb2O10 ceramics

Abstract The quantitative determination and the crystal structure of Ca x Zn 1− x Sn 0.08 Ti 1.92 Nb 2 O 10 ceramics were analyzed by X-ray diffraction, the microwave dielectric properties were investigated. The results showed that the Ca x Zn 1− x Sn 0.08 Ti 1.92 Nb 2 O 10 ceramics contained three main phases: ZnTiNb 2 O 8 phase, Zn 0.15 Nb 0.30 Ti 0.55 O 2 phase and Unknown Columbite-type phase. With the increase of Ca content, the weight fraction of secondary phase Zn 0.15 Nb 0.30 Ti 0.55 O 2 and Unknown Columbite-type phase increased. For ZnTiNb 2 O 8 , with the substitution of Ca 2+ for Zn 2+ , the bond valence of Ti-site increased. The variation of distortion of oxygen octahedral was irregular. For Zn 0.15 Nb 0.30 Ti 0.55 O 2 , the distortion of oxygen octahedral and the bond valence of Ti-site increased with substitution of Ca 2+ . The increase of Ti-site bond valence led to a harder rattling of Ti cations of the specimens. As a result, the dielectric constant ( e ) and the quality factor value ( Qf ) decreased, the temperature coefficient of resonant frequency ( τ f ) moved to the positive direction. The typical values of e = 53.09, Qf = 48,000 GHz, τ f = 21.20 ppm/°C were obtained for Ca x Zn 1− x Sn 0.08 Ti 1.92 Nb 2 O 10 ( x = 0.02) specimens sintered at 1120 °C for 6 h. The relative low sintering temperature and high dielectric properties in microwave range make these ceramics promising for application in multilayer ceramic capacitors.

Crystal structure and microwave dielectric properties of (Zn1−xCox)TiNb2O8 ceramics

The crystal structure and microwave dielectric properties of (Zn1−xCox)TiNb2O8 ceramics have been investigated. The results showed that the (Zn1−xCox)TiNb2O8 ceramics contained two main phases: (Zn,Co)TiNb2O8 phase and (Zn,Co)0.17Nb0.33Ti0.5O2 phase. The microwave dielectric properties of the (Zn1−xCox)TiNb2O8 ceramics were strongly affected by the change of crystal structure of each phase. The (Zn1−xCox)TiNb2O8 (x=0.1, 0.2, 0.3, 0.4) ceramics were sintered at temperatures ranging from 1025 to 1125°C for 4h. With the increase of Co content, the amount of (Zn,Co)0.17Nb0.33Ti0.5O2 phase increased, resulting in the increase of the dielectric constant (εr), decrease of the Q×f value and the temperature coefficient of resonant frequency (τf) moving to the positive direction. The excellent microwave dielectric properties of εr=35.93, Q×f=35,125GHz, τf=0ppm/°C were obtained for the (Zn1−xCox)TiNb2O8 ceramics (x=0.3) sintered at 1075°C for 4h. The relatively low sintering temperature (<1080°C) and high dielectric properties in microwave range make these ceramics promising for application in electronics.

Metal-dielectric nanocomposite structures

The influence of nanocomposite structures Al-polymer at its dielectric properties in microwave range is investigated. The graphs of experimental dependences of transmission and reflection coefficients of electromagnetic waves, the real and the imaginary part of dielectric permittivity of the samples, as well as of the volume fraction of the dispersed phase are represented

Microwave dielectric properties and structure of ZnO–Nb 2O 5–TiO 2 ceramics

Ceramic samples based on ZnO–Nb 2O 5–TiO 2 compositions have been prepared using solid state ceramic route. The work was carried out over a wide range of initial ZnNb 2O 6 and Zn 0.17Nb 0.33Ti 0.5O 2 compounds concentration. The crystal structure and microstructure developments were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was shown that the phase compositions of the samples present itself a columbite type and mixture of two phases—solid solutions of columbite and rutile types.The sintering behavior, permittivity, its temperature coefficients and quality factor had been characterized for ceramic samples in depending on compositions. The permittivity of the samples in this system is within the limits from 24 to 80, τ ɛ from 150 to −560 ppm/°C. For the samples with τ ɛ ∼ 0, ɛ r ∼ 43.8 and Q· f = 35000 GHz at f = 9 GHz. The comparatively low sintering temperature (≤1080 °C) and high dielectric properties in microwave range make these ceramics promising for application in electronics.