Microwave dielectric resonators based on Ba[( Bi,Dl)1/2 Nb1/2]O3 (D= Y, Pr, Sm, Gd, Dy, Er) (original) (raw)
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Microwave dielectric resonators (DRs) based on Ba(B 1/2Nb1/2)O3 [B = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In] complex perovskites have been prepared by conventional solid state ceramic route. The dielectric properties (relative permittivity, εr ; quality factor, Q; and resonant frequency, τf ) of the ceramics have been measured in the frequency range 4–6 GHz using resonance methods. The resonators have relatively high dielectric constant in the range 36–45, high quality factor and small temperature variation of resonant frequency. The dielectric properties are found to depend on the tolerance factor (t), ionic radius (r), and lattice parameter (ap).
Ceramics International, 1995
The (Ba1 Sr,) (Nd;;,Nbl;,) O, ceramics have been prepared by the conventional ceramic route for different values of.v. Addition of a small amount of CeO, (I wt'!/,,) as a sintering aid increased the density of the samples. The structure and microstructure of the sintered samples are studied by X-ray diffraction and SEM methods. The dielectric properties of the samples are measured in the microwave frequency region as a function of composition. The dielectric constant decreases as x increases. The coefficient of thermal variation of resonant frequency decreases as the Sr content increases and goes to the negative side. The dielectric properties of (Bai_,Sr,) (Nd, Nbj) O, are in the range suitable for application as dielectric resonators in microwave circuits.
Ba(Tb12Nb12)O3: A new ceramic microwave dielectric resonator
Materials Letters, 1997
has been prepared and characterized in the microwave frequency region. 1 wt% CeO, is used as additive to reduce the sintering temperature. The sintered samples were characterized by XRD, SEM and Raman spectroscopic methods. Microwave DR properties such as Ed, Q factor and temperature-coefficient of resonant frequency (~~1 have been measured using a HP 8510 B Network Analyzer. Cylindrical DRs of Ba(Tb,,,Nb,,:!)O, showed high E, (-371, high Q (-3,200) and low 7f (-10 ppm/"C) at 4 GHz and hence are useful for practical applications. 0 1997 Elsevier Science B.V.
Ba( Tb1/2Nb1/2) 03: A new ceramic microwave dielectric resonator H.
A new microwave dielectric resonator Ba@b,,,Nb,,,)O, has been prepared and characterized in the microwave frequency region. 1 wt% CeO, is used as additive to reduce the sintering temperature. The sintered samples were characterized by XRD, SEM and Raman spectroscopic methods. Microwave DR properties such as Ed, Q factor and temperature-coefficient of resonant frequency (~~1 have been measured using a HP 8510 B Network Analyzer. Cylindrical DRs of Ba(Tb,,,Nb,,:!)O, showed high E, (- 371, high Q (- 3,200) and low 7f (- - 10 ppm/“C) at 4 GHz and hence are useful for practical applications. 0
Low-loss dielectric ceramics based on Ba(B0 1/2Ta1/2)O3 (B0 5La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) complex perovskites have been prepared by the solid-state ceramic route. The dielectric properties (er, Qu, and tf) of the ceramics have been measured in the frequency range 4–6 GHz by the resonance method. The resonators have a relatively high dielectric constant and high quality factor. Most of the compounds have a low coefficient of temperature variation of the resonant frequencies. The microwave dielectric properties have been improved by the addition of dopants and by solid solution formation. The solid solution Ba[(Y1xPrx)1/2Ta1/2]O3 has x50.15, with er533.2, Quf551,500 GHz, and tf 0. The microwave dielectric properties of Ba(B0 1/2Ta1/2)O3 ceramics are found to depend on the tolerance factor (t), ionic radius, and ionization energy.
Sr(B1/2 0 Nb1/2)O3 [B0 5La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] ceramics were prepared by the conventional solid-state ceramic route. The crystal structure and microstructure of the ceramics were characterized by X-ray diffraction and scanning electron microscopic methods, and the dielectric properties were measured in the microwave range. Addition of a small amount of CeO2 as a sintering aid improved the densification and dielectric properties of the ceramics. The effects of cation substitution and glass addition on the microwave dielectric properties of the ceramics were also investigated. Glass addition resulted in the lowering of the processing temperature of the materials without much affecting the dielectric properties, whereas cation substitution resulted in the variation of the temperature coefficient of resonant frequencies. A correlation of dielectric properties with the tolerance factor and ionic radii of B0-site elements of the ceramics has been observed.
Improvement of microwave dielectric properties for Ba(Ni1/3Nb2/3)O3 ceramics by Zr-substitution
Ceramics International, 2015
Effects of Zr-substitution on the structure, microstructure and microwave dielectric properties of Ba(Ni 1/3 Nb 2/3)O 3 ceramics have been investigated. A small amount of Zr-substitution facilitates the densification of Ba(Ni 1/3 Nb 2/3)O 3 ceramics. Within x ≤ 0.05, the densification temperature decreases with increasing x in Ba[(Ni 1/3 Nb 2/3) 1-x Zr x ]O 3 , while it turns to increase for x>0.05. With increasing x, the grains become more homogeneous and closely contacted, and significantly increase in size for x=0.15-0.20. The B-site cations 1:2 ordering is destroyed by Zr-substitution, and only stabilizes for x ≤ 0.04. B-site cations 1:1 ordering starts to form in x=0.04, and the 1:1 ordering degree first increases and then decreases with increasing x. Q×f value decreases slightly in x=0.01 and then increases monotonously with x increasing from 0.02 to 0.20. The destroyed 1:2 ordering structure is responsible for the decreased Q×f value in x=0.01; while the improved grain configuration dominates the increase of Q×f value for x=0.02-0.20. The dielectric constant ε r increases monotonously with increasing x, due to the higher polarizability of Zr ion than the average value of Ni/Nb ions. The temperature coefficient of resonant frequency τ f shifts from negative to positive through zero with increasing x, which is ascribed to the highly positive τ f value of the end member BaZrO 3. The significant improvement of microwave dielectric properties has been achieved for x=0.10, higher ε r , higher Q×f as well as near zero τ f value have been obtained: ε r =31.8, Q×f =36,100 GHz, τ f =7.8 ppm/ o C.
Influence of Bi2O3 and MnO2 doping on microwave properties of (Pb,Ca) LaO3 dielectric ceramics
Materials Science and Engineering: B, 2005
The effect of Bi 2 O 3 and MnO 2 addition in [(Pb 0.5 Ca 0.5) 0.92 La 0.08 ](Fe 0.5 Nb 0.5)O 3 system on the sintering and dielectric properties have been investigated using X-ray diffractions and post-resonator measurement. Perovskite and pyrochlore phase exist in samples with MnO 2 content ≤2 wt.% while specimens with Bi 2 O 3 doping possessed the third unknown phase. The dielectric properties could be obviously adjusted as well as reducing the sintering temperature in both Bi 2 O 3 and MnO 2 addition system. It was found that Bi 2 O 3 and MnO 2 co-doping could reduce the sintering temperature more effectively by 100-140 • C while improve the microwave dielectric properties. Microwave dielectric properties of ε r = 91.1, Qf = 4870 GHz and τ f = 18.5 ppm/ • C could be obtained in [(Pb 0.5 Ca 0.5) 0.92 La 0.08 ](Fe 0.5 Nb 0.5)O 3 system when k = 1, w = 1 wt.% and sintered at 1050 • C for 4 h.