Microwave Dielectric Properties Of Ca Research Articles

Microwave Dielectric Properties of B<sub>2</sub>O<sub>3</sub> Doped Ca [(Li<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.9</sub><sub>5</sub>Zr<sub>0.0</sub><sub>5</sub>]O<sub>3</sub><sub>−δ </sub>Ceramics

The effects of B2O3 on the sinterability and microwave dielectric properties of Ca [(Li1/3Nb2/3)0.95Zr0.05]O3−δ ceramics were investigated. B2O3 doping can effectively reduce sintering temperatue by 150~200oC. The temperature coefficient of resonator frequency τf increased with an increase of B2O3 content and sintering temperatue. When B2O3 of 2wt% were added, the optimum microwave dielectric properties: εr=28.7,Qf =13580GHz and τf= − 7.8×10−6/oC were obtained at the sintering temperature of 950oC.

Synthesis and microwave dielectric properties of Ca substituted SrLa4Ti4·93Zr0·07O17 ceramics

Microwave dielectric ceramics in Sr1–x Ca x La4Ti4·93Zr0·07O17 (0 ≤ x ≤ 0·5) composition series were processed via a solid-state sintering rout. X-ray diffraction revealed single phase ceramics. Ca substitutions for Sr tuned τ f towards zero with increased Q u f o values. In the present study, ε r ~ 55, Q u f o ~ 11960 GHz and τ f ~ 5·2 ppm/°C were achieved for the composition with x = 0·3.

Effect of Excess Li+ on Microwave Dielectric Properties of Ca0.16Sr0.04Li0.4Nd0.4TiO3 Ceramics

The effect of excess Li+ (δ) on microstructures and microwave dielectric properties of Ca0.16Sr0.04Li0.4Nd0.4TiO3 ceramics with δ = 0.00125–0.0125 was investigated. XRD analysis showed that lattice parameters in a‐axis, b‐axis, and c‐axis became longer by the addition of small amount of excess Li+. Ca0.16Sr0.04Li0.4Nd0.4TiO3 ceramics with δ = 0.0075 after being sintered at 1270°C showed the optimal values with εr = 138, Q.f = 1591 GHz, and τf = 52 ppm/°C. Impedance measurement indicated that the grain regions showed the inhomogeneity in electrical properties and dielectric loss of the ceramic system were mainly derived from the semiconducting grain cores.

Structure and microwave dielectric properties of Ca0·7Ti0·7La0·3(Al0·3−xGax)O3 ceramics

Microwave dielectric ceramics in the system Ca0·7Ti0·7La0·3(Al0·3−xGax)O3 were prepared by the mixed oxide route. Powders were calcined at 1200°C and sintered at 1500°C for 4 h. High density products, at least 93% theoretical, were obtained for substitutions in the range 0·03⩽x⩽0·20. The microstructures of the ceramics had grain sizes in the range of 4–15 μm, and those with a high level of substitution (0·1–0·2) contained a grain boundary phase rich in Al–Ga. All the samples were orthorhombic in structure (Pbnm). The dielectric properties improved with Ga substitution; for x = 0·03, ϵr = 45±0·5, Q×f = 39 900±2000 GHz and τf = +12±0·5 ppm °C−1; for x = 0·2, ϵr = 50±0·5, Q×f = 26 400±1320 GHz and τf = 18±0·5 ppm °C−1. Electron diffraction patterns revealed the presence of (112), () and (110) type twins.

Structures and microwave dielectric properties of Ca(1−x)Nd2x/3TiO3 ceramics

Abstract Ca (1− x ) Nd 2 x /3 TiO 3 microwave dielectric ceramics were prepared by the mixed oxide route; powders were calcined at 1100 °C and sintered at 1450–1500 °C. High density, single phase products were obtained for all compositions. Grain sizes ranged from 1 μm to 100 μm. There was evidence of significant discontinuous grain growth in mid range compositions; all ceramics were characterised by complex domain structures. With increasing Nd content there was a evidence of a transition from an orthorhombic Pbnm structure to a monoclinic C2/m structure. This was accompanied by a decrease in relative permittivity ( ɛ r ) from 180 to 78, and decrease in the temperature coefficient of resonant frequency ( τ f ) from +770 ppm K −1 to +200 ppm K −1 . The product of dielectric Q value and resonant frequency ( Q × f ) varied in a grossly non-systematic way, exhibiting a peak at 13,000 GHz in Ca 0.7 Nd 0.2 TiO 3 .

Preparation and Microwave Dielectric Properties of Ca(Sm<sub>0.5</sub>Nb<sub>0.5</sub>)O<sub>3</sub> Ceramics

Microstructures and microwave dielectric properties of Ca(Sm0.5Nb0.5)O3 ceramics, prepared by a conventional solid-state reaction method, were systematically investigated by varying calcining temperature, sintering temperature and cooling rate. The XRD result showed that a single Ca(Sm0.5Nb0.5)O3 phase could be synthesized at a calcining temperature of 1200 °C. Optimized combination of microwave dielectric properties of εr = 22.36, Q×f = 18030 GHz and τf = -31.2 ppm/°C was obtained for furnace-cooled Ca(Sm0.5Nb0.5)O3 ceramics sintered at 1550 °C for 4 h. However, some microcracks were found from the microstructures of the furnace-cooled specimens. Further, the Q×f value could be increased by controlling the cooling rate during the sintering process due to the disappearance of microcracks in the final material. With a cooling rate of 2 °C/min, Ca(Sm0.5Nb0.5)O3ceramics exhibited an enhanced Q×f value of 37130 GHz.

Microwave Dielectric Properties of Low-Temperature Sintered Ca[(Li<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.95</sub>Zr<sub>0.05</sub>]O<sub>3−δ</sub>−0.04TiO<sub>2</sub> Ceramics

The effects of B2O3 on the sinterability and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.95Zr0.05]O3−δ−0.04TiO2 (CLNZ−0.04TiO2) ceramics were investigated . B2O3 doping can effectively reduce sintering temperatue by 150~200°C. The temperature coefficient of resonator frequency τf increased with an increase of B2O3 content and sintering temperatue. When B2O3 of 2wt% were added, the optimum microwave dielectric properties: εr =31.8,Qf =17240GHz and τf = − 5.9×10−6/°C were obtained at the sintering temperature of 950°C.

Effect of Glass Additions on Ca[(Li<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.92</sub>Zr<sub>0.08</sub>]O<sub>3−δ</sub> Microwave Ceramics

The effects of ZnO-B2O3-Na2O(ZBN) glass on the sinterability and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.92Zr0.08]O3−δ ceramics were investigated . ZBN glass doping can effectively reduce sintering temperatue by 100~150°C. The temperature coefficient of resonator frequency τf increased with an increase of ZBN glass content and sintering temperatue. When ZBN glass of 1.8wt% were added, the optimum microwave dielectric properties: εr =22.1,Qf =18360GHz and τf = − 9.8×10−6/°C were obtained at the sintering temperature of 1000°C.

Microwave sintering of Ca0.6La0.2667TiO3 microwave dielectric ceramics

Ca0.6La0.2667TiO3 ceramics were prepared by conventional and microwave sintering techniques and their sinterability, microstructure, and microwave dielectric properties were investigated in detail for comparison. Densified Ca0.6La0.2667TiO3 ceramics were obtained by microwave sintering at 1350°C for 30 min and by conventional sintering at 1450°C for 4 h. An unusual phenomenon was found that some larger grains (grain size range: 8–10 μm) inclined to assemble in one area but some smaller ones (grain size range: 2–4 μm) inclined to gather in another area in the microwave sintered ceramics. The microwave dielectric properties of Ca0.6La0.2667TiO3 ceramics prepared by microwave sintering at 1350°C were as follows: dielectric constant (ɛr) = 119.6, quality factor (Qf) = 17858.5 GHz, and temperature coefficient of resonant frequency (τf) = 155.5 ppm/°C. In contrast, the microwave dielectric properties of the ceramics prepared by conventional sintering at 1450°C were ɛr = 117.4, Qf = 13375 GHz, and τf = 217.2 ppm/°C.

Low temperature cofirable Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ microwave dielectric ceramic with ZnO–B2O3–SiO2 frit

The sintering properties and microwave dielectric properties of Ca[(Li1/3Nb2/3)1−xZr3x]O3+δ (x=0.05, abbreviated as CLNZ) ceramic doped with ZBS frit are investigated for LTCC applications. XRD patterns and SEM photographs show that dense and single perovskite phase ceramics can be obtained with ZBS doping content of less than 10wt%, before the Ca2Nb2O7 pyrochlore phase begins to segregates. The results show that ZBS vitreous phase stays at the grain boundary in the final sintered ceramics, suggesting it acts as liquid phase lubrication during sintering, and has effectively lowered the sintering temperature of CLNZ ceramics from 1170°C to 940°C. The preferred orientation of CLNZ solid solution varies from (121) plane to (101) plane as ZBS content and sintering temperature increase. The optimal microwave dielectric properties of ɛr=32.0, Qf=6.64THz and τf=−27.1ppm/°C can be obtained in 15wt% ZBS doped CLNZ ceramic when sintered at 940°C for 4h. The Ag-cofiring experiment clearly shows that no chemical reaction takes place between Ag and the ZBS-doped CLNZ ceramic, indicating its great potential applications in LTCC field.

Effect of B<sub>2</sub>O<sub>3</sub> on Microwave Dielectric Properties of Ca[(Li<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.92</sub>Zr<sub>0.08</sub>]O<sub>3−δ</sub>−0.05TiO<sub>2</sub> Ceramics

The effects of B2O3 on the sinter ability and microwave dielectric properties of Ca [(Li1/3Nb2/3)0.92Zr0.08]O3−δ−0.05TiO2 (CLNZ−0.05TiO2) ceramics were investigated. B2O3 doping can effectively reduce sintering temperature by 150~200 °C. The temperature coefficient of resonator frequency τf increased with an increase of B2O3 content and sintering temperature. When B2O3 of 2.5 wt % were added, the optimum microwave dielectric properties: εr =34.2, Qf =15680GHz and τf = − 4.7×10−6/°C were obtained at the sintering temperature of 950 °C.

Microwave Dielectric Properties of Ca[(Li<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.95</sub>Zr<sub>0.05</sub>]O<sub>3−δ−x</sub>TiO<sub>2</sub> Ceramics

Crystal structure and microwave dielectric properties of Ca [(Li1/3Nb2/3) 0.95Zr0.05]O3−δ−xTiO2(0≤x≤0.1) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.02~0.1. With an increasing of Ti4+ content, the Qf value decreased due to a decrease of the degree of B-site 1:2 ordering. However, the τf value increased from-14.7ppm /°C to-6.9ppm/°C. When x=0.04, the optimum microwave dielectric properties: εr=31.1, Qf =21640GHz and τf =−8.8 ppm/°C.

Synthesis and microwave dielectric properties of Ca0.6La0.267TiO3 nanocrystalline powders by sol–gel method

Ca0.6La0.267TiO3 nanocrystalline powders were successfully synthesized by the sol–gel method using PEG1000 as a dispersant in this study. The sinterability of the powders and the microwave dielectric properties of the ceramics were also investigated. The XRD diffraction result showed that pure Ca0.6La0.267TiO3 powder with orthorhombic perovskite structure could be synthesized at 600 °C for 2 h without any detectable intermediate phase. The average grain size of the as-synthesized powder was as low as 35 nm. Compared with Ca0.6La0.267TiO3 ceramics fabricated by conventional solid-state process, the bulk materials prepared by sintering as-prepared nanopowders performed better in densification and microwave dielectric properties. The ceramics sintered at 1,300 °C exhibited a higher relative density of 98.3% combined with a dielectric constant (er) of 120.3, a quality factor (Q × f) of 23,550 GHz and a temperature coefficient of resonant frequency (τf) of +220.7 ppm/°C, respectively.

Influence of ZnO-B<sub>2</sub>O<sub>3</sub>-Na<sub>2</sub>O Glass on Microwave Dielectric Properties of Ca[(Li<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.8</sub>Sn<sub>0.2</sub>]O<sub>3−δ</sub>−0.1TiO<sub>2</sub> Ceramics

The effects of ZnO-B2O3-Na2O(ZBN) glass on the sinterability and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.8Sn0.2]O3−δ−0.1TiO2 (CLNS−0.1TiO2) ceramics were investigated . ZBN glass doping can effectively reduce sintering temperatue by 100~150°C. The temperature coefficient of resonator frequency τf increased with an increase of ZBN glass content and sintering temperatue. When ZBN glass of 3wt% were added, the optimum microwave dielectric properties: εr =28.8,Qf =10960GHz and τf = − 7.5×10−6/°C were obtained at the sintering temperature of 1050°C.

Crystal Structure and Microwave Dielectric Properties of Ca[(Li1/3Nb2/3) 0.92Zr0.08]O3-δ−xTiO2 Ceramics

Crystal structure and microwave dielectric properties of Ca[(Li1/3Nb2/3) 0.92Zr0.08]O3−δ−xTiO2(0≤x≤0.2) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.0~0.1. With an increasing of Ti4+ content, the Qf value decreased due to a decrease of the degree of B-site 1:2 ordering. However, the τf value firstly increased from-14.2ppm /°C to -6.6ppm/°C, and then moved to the negative direction. When x=0.05, the optimum microwave dielectric properties: εr=32.8, Qf =19460GHz and τf =−8.3 ppm/°C.

Investigation of the microwave dielectric properties of Ca 1− xMg xLa 4Ti 5O 17 ceramics for application in coplanar patch antenna

In this paper, the dielectric properties of Ca 1− x Mg x La 4Ti 5O 17 ceramics at microwave frequency have been studied. The diffraction peaks of Ca (1− x) Mg x La 4Ti 5O 17 ceramics nearly unchanged with x increasing from 0 to 0.03. Similar X-ray diffraction peaks of Ca 0.99Mg 0.01La 4Ti 5O 17 ceramic were observed at different sintering temperatures. A maximum density of 5.3 g/cm 3 can be obtained for Ca 0.99Mg 0.01La 4Ti 5O 17 ceramic sintered at 1500 °C for 4 h. A maximum dielectric constant ( ɛ r ) and quality factor ( Q × f) of Ca 0.99Mg 0.01La 4Ti 5O 17 ceramic sintered at 1500 °C for 4 h are 56.3 and 12,300 GHz (at 6.4 GHz), respectively. A near-zero temperature coefficient of resonant frequency ( τ f ) of −9.6 ppm/°C can be obtained for Ca 0.99Mg 0.01La 4Ti 5O 17 ceramic sintered at 1500 °C for 4 h. The measurement results for the aperture-coupled coplanar patch antenna at 2.5 GHz are presented. With this technique, a 3.33% bandwidth (return loss <−10 dB) with a center frequency at approximately 2.5 GHz has been successfully achieved.

Zero Temperature Compensated Microwave Dielectric Properties of Ca0.8Sr0.2TiO3–Li0.5Ln0.5TiO3 System

The microwave dielectric properties of (1 – x) Ca 0.8 Sr 0.2 TiO 3 + xLi 0.5 Ln 0.5 TiO 3 (CST-LLT) (x = 0–1.0) (Ln: Nd, Sm) system have been investigated. The dielectric constant (ϵ r ) decreased with x increasing. The temperature coefficient of resonant frequency (τ f ) decreased almost linearly from high positive values to negative values with the increase of x. A near zero τ f was achieved at x = 0.87 for Nd and x = 0.81 for Sm ions, respectively. Optimized microwave dielectric properties (ϵ r = 111.6; Q × f = 2013 GHz; τ f = – 2.75 ppm/°C) of CST-LNT and (ϵ r = 95; Q × f = 3303 GHz; τ f = – 1.8 ppm/°C) of CST-LST were estimated at x = 0.87 and x = 0.81 respectively.

DIELECTRIC PROPERTIES OF Ca(1-x)ZnxLa4Ti5O17 CERAMICS AT MICROWAVE FREQUENCIES

In this paper, the microwave dielectric properties of Ca (1- x ) Zn x La 4 Ti 5 O 17 ceramics have been studied. The diffraction peaks of Ca (1- x ) Zn x La 4 Ti 5 O 17 ceramics shift to higher angles as x increases from 0 to 0.01 and nearly unchanged with x increasing from 0.01 to 0.03. A maximum density of dielectric constant value of 57 and a quality factor ( Q × f ) of 15000 GHz can be obtained for Ca 0.99 Zn 0.01 La 4 Ti 5 O 17 ceramic sintered at 1450°C for 4h. A near-zero temperature coefficient of resonant frequency (τ f ) of -8.1 ppm/°C can be obtained for Ca 0.99 Zn 0.01 La 4 Ti 5 O 17 ceramic sintered at 1450°C for 4h.

Influence of CuO or MnCO3 additive on the dielectric properties of Ca0.65Ti0.65La0.35Al0.35O3 Ceramics

The influence of CuO or MnCO3 additive on the sinterability, microstructure and microwave dielectric properties of Ca0.65Ti0.65La0.35Al0.35O3, i.e., CTLA, ceramics was investigated in this paper. The results indicated that the density and dielectric properties of CTLA ceramics can be improved by both low-level doping of CuO (up to 1 wt%) and MnCO3 (up to 0.75 wt%). The sintering temperature of CTLA ceramics with addition of CuO/MnCO3 can be effectively reduced from 1450°C to 1320°C due to the liquid phase effect. No secondary phase was observed for the addition at the amount of 0.5-1 wt% CuO and 0.25-0.75 wt% MnCO3. With the addition of CuO/MnCO3, the dielectric constant (er) and the temperature coefficient of resonant frequency (tf) of the samples were not significantly affected, while the unloaded quality factors Q were effectively promoted. Excellent microwave dielectric properties were achieved for the ceramic Ca0.65Ti0.65La0.35Al0.35O3 + 0.75wt% CuO/ MnCO3 sintered at 1320°C for 2 h, with values of Q×f = 32,800 GHz, er = 43 and tf = +10 ppm/°C.

Influence of CuO Addition and Sintering Temperature on Microwave Dielectric Properties of Ca0.99Zn0.01La4Ti5O17 Ceramics for Application in Stacked Patch Antenna

In this study, the microwave dielectric properties of Ca0.99Zn0.01La4Ti5O17 (CZLTO) ceramics have been investigated. It is found that the X-ray diffraction pattern exhibited no phase difference with 0.5 wt % CuO additive at different sintering temperatures. The maximum value of the dielectric constant and the quality factor Q×f can be obtained with 0.5 wt % CuO additive and sintered at 1450 °C for 4 h. A τf of -8.16 ppm/°C was measured for CZLTO ceramics with 0.5 wt % CuO sintered at 1450 °C for 4 h. The measurement results for a stacked patch antenna at 2.45 GHz are presented. With this technique, a 3.3% bandwidth (return loss < -10 dB) with a center frequency at approximately 2.45 GHz has been successfully achieved. The peak antenna gain is approximately 2.2 dBi, with gain variations of less than 1.0 dBi for frequencies within in the -10 dB S11 bandwidth.