Microwave dielectric properties of CeO2–0.5AO–0.5TiO2 (A = Ca, Mg, Zn, Mn, Co, Ni, W) ceramics (original) (raw)
Related papers
Microwave dielectric properties of (1x)CeO2–xCaTiO3 and (1x)CeO2–xSm2O3 ceramics
CeO2–CaTiO3 and CeO2–Sm2O3 microwave dielectric ceramics have been prepared by a conventional solid state ceramic route. The dielectric ceramics are characterized by X-ray diffraction, SEM, Raman and microwave methods. Ceria has a relative dielectric constant, "r, of 23, high dielectric quality factorfrequency product, Qf up to 60,000 GHz withh igh temperature coefficient of resonant frequency, f, of 53 ppm/C. The addition of CaTiO3 and samarium oxide leads to a zero temperature variation of resonant frequency. The relative dielectric constant increases and Q decrease withCaTiO 3 addition and the r changes from a negative to a positive value. Sm2O3 addition of up to 50 mol% increases Q, decreases "r and improves the f. The microwave dielectric properties are measured at low temperatures down to 20 K. The effect of addition of 1 mol% of various rare earth oxides on the microwave dielectric properties of ceria has also been investigated
The (1−x)CeO2–xRE2O3 (RE = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb and Y), 0≤x≤1 ceramics have been prepared by solid state ceramic route. The solubility of different rare earths (RE) in ceria was investigated by using XRD, SEM and EDXA techniques. The microwave dielectric properties of the ceramics having different compositions were investigated. Several high Q dielectric resonator compositions were identified in (1−x)CeO2–xRE2O3 (RE = La, Nd, Sm, Eu, Gd, Dy, Er, Tm, Yb and Y), ceramics for 0≤x≤1. The best properties were obtained for 0.9CeO2–0.1Eu2O3 (εr = 25.4, Qu ×f = 70,300 GHz, f =−64 ppm/◦C), 0.8CeO2–0.2Dy2O3 (εr = 26.2, Qu ×f = 70,150 GHz, f =−57 ppm/◦C) and 0.3CeO2–0.7Sm2O3 (εr = 19.7, Qu ×f = 79,450 GHz, f =−51 ppm/◦C).
Microwave Dielectric Properties and Low-Temperature Sintering of Cerium Oxide for LTCC Applications
were added to CeO 2 powder. The crystal structure of the ceramic-glass composites was studied by X-ray diffraction, microstructure by scanning electron microscopy, and phase composition using the energy-dispersive X-ray analysis technique. The microwave dielectric properties such as relative permittivity (e r ), quality factor (Q u xf), and coefficient of temperature variation of resonant frequency (s f ) of the ceramics have been measured in the frequency range 4-6 GHz. Addition of B 2 O 3 and Bi 2 O 3 -ZnO-B 2 O 3 -SiO 2 lowered the sintering temperature of ceria to about 9001C. The 20 wt% B 2 O 3 and 10 wt% Bi 2 O 3 -ZnO-B 2 O 3 -SiO 2 -added CeO 2 and sintered at 9001 and 9501C showed: Q u xf 5 24 200 and 12 000 GHz, e r 5 13.2 and 22.4, and s f 5 À46 and -57.2 ppm/1C, respectively.
Journal of the American Ceramic Society, 2004
Cerium oxide (CeO 2 ) has been prepared as a ceramic dielectric resonator by a conventional solid-state ceramic route. The sintered CeO 2 has a high dielectric quality factor (Q؋f), Q value of 10 000 at 6 GHz with a relative permittivity () of 23, and temperature coefficient of resonant frequency ( f ) of ؊53 ppm/°C. The Q value increases to 20 000 at 6 GHz when the CeO 2 is doped with 1 mol% CaCO 3 . Higher levels of CaCO 3 doping lowers the Q and values and simultaneously decreases f . TiO 2 doping decreases f and slightly increases , but deceases the Q value. The Q value of pure CeO 2 increases to 105 000 at a frequency of 5.58 GHz when it is cooled to 30 K, whereas Q Ϸ 85 000 at 5.48 GHz for 1-mol%-CaCO 3 -doped CeO 2 at 30 K.
Microwave Dielectric Properties and Low-Temperature Sintering of (1x)CeO2xBaTi4O9 Ceramics
(1x)CeO2xBaTi4O9 ceramics were prepared by the solid-state ceramic route. The structure and microstructure of the ceramics were studied using X-ray diffraction (XRD) and scanning electron microscope. XRD patterns indicate that (1x) CeO2xBaTi4O9 ceramics were of a two-phase composite consisting of fluorite CeO2 and BaTi4O9. The microwave dielectric properties such as relative permittivity (er), quality factor (Quf ), and coefficient of temperature variation of resonant frequency (tf ) of the ceramics have been measured in the frequency range 4–6 GHz by the resonance method. The 0.5CeO2– 0.5BaTi4O9 samples sintered at 12601C/2 h exhibit excellent microwave dielectric properties: er534.5, Quf520,750 GHz (at 4.2 GHz) and tf51.8 ppm/1C. The density, dielectric constant, and temperature coefficient of resonant frequency of mixtures predicted by the appropriate mixing relations agree well with the experimental values. The addition of B2O3 and CuO significantly lowered the sintering temperature of 0.5CeO2–0.5BaTi4O9 ceramic to 9501C. The 0.5CeO2–0.5 BaTi4O9112 wt% B2O311 wt% CuO sintered at 9501C for 4 h showed er520.6, Quf517,000 GHz (at 5.7 GHz) and tf5148 ppm/1C.
Microwave dielectric properties of BaO−2CeO2−nTiO2 ceramics
Journal of Solid State Chemistry, 2004
The BaO-2CeO2-nTiO2 ceramics with n = 3, 4 and 5 have been prepared with CeO2 as starting material. The ceramics have been characterized using scanning electron microscopy , X-ray diffraction , Raman and X-ray photoelectron spectroscopy techniques. The microwave dielectric properties have been measured using standard dielectric resonator techniques. BaO-2CeO2-3TiO2 (123), BaO-2CeO2-4TiO2 (124) and BaO-2CeO2-5TiO2 (125) ceramics showed dielectric constants of 38, 27 and 32, respectively. All the ceramics showed fairly good unloaded Q-factors. 124 and 125 compounds exhibited low tf values, while 123 showed a high rf value.
Synthesis, characterization and microwave dielectric properties of nanocrystalline CaZrO 3 ceramics
Journal of Alloys and Compounds, 2008
Spinel MgGa 2 O 4 ceramic materials were synthesized by solid-state method. MgGa 2 O 4 powders were investigated with X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, Raman spectrum, X-ray photoelectron spectrum (XPS), and high resolution transmission electron microscopy (HRTEM). The spinel-structured MgGa 2 O 4 ceramics sintered at 1410°C exhibited excellent microwave dielectric properties: a dielectric constant (e r ) of 9.54, a quality factor (Q Â f) of 117,000 GHz (at 14.7 GHz frequency) and a temperature coefficient of resonant frequency (s f ) of À4.0 ppm/°C. MgGa 2 O 4 ceramics have a wide sintering temperature region ($150°C) and nearly zero s f value. The large relative density, uniform microstructure and cation ordering resulted in high Q Â f values. Crystal distortion from the oriented growth was advantageous to produce nearly zero s f value. MgGa 2 O 4 ceramics are promising candidate materials for millimeter-wave devices. j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j a l c o m solution. 0.79ZnAl 2 O 4 -0.21Mg 2 TiO 4 ceramics (sintered at 1550°C) had the following dielectric properties: e r = 9.6, Q Â f = 160,800 GHz, s f = À65.3 ppm/°C [18].
Materials Science-Poland, 2014
Ca 2 Ce 2 Ti 5 O 16 dielectric ceramics prepared by conventional solid-state ceramic route was investigated. Phase composition and microwave dielectric properties were measured using XRD and Vector network analyzer, respectively. XRD analysis of the calcined and sintered samples revealed the formation of CeO 2 and another unidentified phase (that vanished at 1400°C) as secondary phases along with the parent Ca 2 Ce 2 Ti 5 O 16 phase. The amount of the parent Ca 2 Ce 2 Ti 5 O 16 phase increased with increasing sintering temperature from 1350°C to 1450°C accompanied by a decrease in the apparent density. The density decreased but ε r and Q u f o increased with sintering temperature. An ε r ∼ 81.5, Q u f o ∼ 5915 GHz and τ f ∼ 219 GHz were achieved for the sample sintered at 1450°C.
2014
Ca2Ce2Ti5O16 ceramics processed via mix oxide route was investigated. Phase composition and microwave dielectric properties were measured using X-ray diffraction and a cavity method, respectively. CeO2 and another unidentified phase (that vanishes at ≥1400 o C) existed as secondary phases along with the parent Ca2Ce2Ti5O16 phase. The amount of the parent Ca2Ce2Ti5O16 phase increased with increasing sintering temperature from 1350 o C to 1450 o C accompanied by a decrease in the apparent density. The density decreased but r and Qufo increased with sintering temperature. An r ~87.2, Qufo~ 5915 GHz and f~219 GHz was achieved for the sample sintered at 1450 o C.
Microwave Dielectric Properties of Ca1+xCu3Ti4O12+x (-0.04 ≤ x ≤ 0.04) Ceramics
Procedia Chemistry, 2016
Ca 1+x Cu 3 Ti 4 O 12+x (-0.04 ≤ x ≤ 0.04) ceramics were prepared by using conventional solid-state route. The microwave dielectric properties of the samples were investigated as a function of measured frequency and the Ca content. A pure perovskite structure was obtained for samples with-0.02 ≤ x ≤ 0.02, whereas small amount of CuO and CaTiO 3 appeared in the samples with x =-0.04 and 0.04, respectively, indicated that the solubility limit of Ca atom in CCTO lattice was reached for this system. Adjusting of Ca content showed a little influence on the microstructure of the ceramics. The sample with x = 0 exhibited good microwave dielectric permittivity (ε' ~ 85), which nearly constant at a broad frequency range of 1-35 GHz, then abruptly dropped to ~70 at 50 GHz. The other samples showed a strongly frequency dependence of dielectric permittivity from ~100 (at 1 GHz) to ~10 (at 50 GHz). The dielectric loss (tan-δ) for nonstoichiometry CCTO samples is relatively higher at least an order of magnitude and displays strong frequency dependence as compared with the x = 0 sample. The existence of vacancy (oxygen and Ca) and Ca/Cu disorder are the main factor affecting ε' and tan-δ values of the ceramics.