Influence of Ba2+ substitution on the microwave dielectric properties of Nd(Mg0.5Sn0.5)O3 ceramics

The microwave dielectric properties of Nd(Mg_0.5?xBa_xSn_0.5)O₃ ceramics were examined with a view to their exploitation in mobile communication. The Nd(Mg_0.5?xBa_xSn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Nd(Mg_0.47Ba_0.03Sn_0.5)O₃ ceramics revealed no significant variation of phase with sintering temperatures. A density of 6.91 g/cm³, a dielectric constant (ε _r ) of 19.14, a quality factor (Q × f) of 97,500 GHz, and a temperature coefficient of resonant frequency (τ _f ) of ?65.4 ppm/°C were obtained for Nd(Mg_0.47Ba_0.03Sn_0.5)O₃ ceramics that were sintered at 1,600 °C for 4 h.     

Improved microwave dielectric properties of Nd(Mg0.5Sn0.5)O3 ceramics with Ni2+ substituting

This study elucidates the microwave dielectric properties and microstructures of Nd(Mg_0.5?xNi_xSn_0.5)O₃ ceramics with a view to their potential for microwave devices. The Nd(Mg_0.5?xNi_xSn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Nd(Mg_0.43Ni_0.07Sn_0.5)O₃ ceramics revealed no significant variation of phase with sintering temperatures. A dielectric constant ( $ \varepsilon_{r} $ ) of 19.3 and a quality factor (Q × f) of 93,400 GHz and a temperature coefficient of resonant frequency ( $ \tau_{f} $ ) of ?66 ppm/ °C were obtained for Nd(Mg_0.43Ni_0.07Sn_0.5)O₃ ceramics that were sintered at 1,550 °C for 4 h.     

Enhancing the microwave dielectric properties of Nd (Mg0.5Sn0.5)O3 ceramics by substituting Nd3+ with Ca2+

The microwave dielectric properties of Nd_(1?2x/3)Ca_x(Mg_0.5Sn_0.5)O₃ ceramics were examined to evaluate their exploitation for mobile communication. Nd_(1?2x/3)Ca_x(Mg_0.5Sn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Nd_2.9/3Ca_0.05(Mg_0.5Sn_0.5)O₃ ceramics revealed no significant variation of phase with the sintering temperature. Nd_2.9/3Ca_0.05(Mg_0.5Sn_0.5)O₃ ceramics that were sintered at 1,550 °C for 4 h had the following properties: a density of 6.86 g/cm³, a dielectric constant (ε_r) of 19.3, a quality factor (Q × f) of 99,000 GHz, and a temperature coefficient of resonant frequency (τ _f ) of ?65 ppm/°C.     

Improved microwave dielectric properties of La(Mg0.5Sn0.5)O3 ceramic with Ba2+ substitution

The microwave dielectric properties of La(Mg_0.5?xBa_xSn_0.5)O₃ ceramics were examined with a view to their exploitation for wireless communications. The La(Mg_0.5?xBa_xSn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The La(Mg_0.5?xBa_xSn_0.5)O₃ ceramics contained La₂Sn₂O₇. An apparent density of 6.54 g/cm³, a dielectric constant ( $ \varepsilon_{r} $ ε r ) of 20.1, a quality factor (Q  $ \times $ ×  f) of 51,600 GHz, and a temperature coefficient of resonant frequency ( $ \tau_{f} $ τ f ) of ?82 ppm/°C were obtained for La(Mg_0.43Ba_0.07Sn_0.5)O₃ ceramics that were sintered at 1,550 °C for 4 h.     

Tuning the microwave dielectric properties of La0.97Sm0.03(Mg0.5Sn0.5)O3 by adding Ca0.8Sm0.4/3TiO3

The influence of sintering temperature on the microwave dielectric properties and microstructure of the (1 ? y)La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃–yCa_0.8Sm_0.4/3TiO₃ ceramic system were investigated with a view to their application in microwave devices. The (1 ? y)La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃–yCa_0.8Sm_0.4/3TiO₃ ceramic systems were prepared using the conventional solid-state method. The X-ray diffraction (XRD) patterns of the (1 ? y)La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃–yCa_0.8Sm_0.4/3TiO₃ ceramic system did not significantly vary with sintering temperature. The XRD patterns of the (1 ? y)La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃–yCa_0.8Sm_0.4/3TiO₃ ceramic system shifted to higher angle as y increased. A dielectric constant of 37.5, a quality factor (Q × f) of 40,300 GHz, and a temperature coefficient of resonant frequency of 2.4 ppm/°C were obtained when the 0.425La_0.97Sm_0.03(Mg_0.5Sn_0.5)O₃–0.575Ca_0.8Sm_0.4/3TiO₃ ceramic system was sintered at 1,600 °C for 4 h.     

Effect of TiO2 and Al2O3 doping on sintering behavior and microwave dielectric properties of Ba4(Sm0.5Nd0.5)28/3Ti18+xO54+2x ceramics

The effects of TiO₂ and Al₂O₃ doping on the phase formation, the microstructure and microwave dielectric properties of Ba_6?3x (Sm_1?y ,Nd _y )_8+2x Ti₁₈O₅₄ (x = 2/3 and y = 0.5; BSNT) ceramics were investigated. X-ray diffraction patterns showed that the main crystal phase of BSNT + xTiO₂ (x = 0–2) ceramics sintered at 1,280 and 1,300 °C for 5 h was Ba(Sm, Nd)₂Ti₄O₁₂, accompanied by a small number of second phases: Ba₂Ti₉O₂₀ and TiO₂ (x ≥ 1.0), while the new phase BaAl₂Ti₅O₁₄ appeared and the two phases Ba₂Ti₉O₂₀ and TiO₂ disappeared in BSNT ? 2TiO₂ ceramic doped with ≥2 wt% Al₂O₃ successively as identified by scanning electron microscopy and energy dispersive spectroscopy analysis. The TiO₂ and Al₂O₃ working as sintering aids conduced effectively to promote the densification and grain growth, and thus decreasing the sintering temperature, so when the amounts of TiO₂ was increased, Q × f and τ _f values increased continuously. The BSNT ? 2TiO₂ ceramics doped with y wt% Al₂O₃ decreased the density and dielectric constant, increased the Q × f value remarkably and the τ _f values was adjusted from 25.3 to ?7.3 ppm/ °C. When doped with 1.5 wt% Al₂O₃ sintered at 1,260 °C for 5 h, the ceramics obtained the excellent microwave dielectric properties: ε _r  = 74.3, Q × f = 11,928 GHz, and τ _f  = +5.39 ppm/ °C.     

Tuning the microwave dielectric properties of La(Mg0.4Sr0.1Sn0.5)O3 by introducing Ca0.8Sr0.2TiO3

The influence of sintering temperature on the microwave dielectric properties and microstructure of the (1 ? y)La(Mg_0.4Sr_0.1Sn_0.5)O₃–yCa_0.8Sr_0.2TiO₃ ceramic system were investigated with a view to their application in microwave devices. The (1 ? y)La(Mg_0.4Sr_0.1Sn_0.5)O₃–yCa_0.8Sr_0.2TiO₃ ceramic systems were prepared using the conventional solid-state method. The X-ray diffraction patterns of the (1 ? y)La(Mg_0.4Sr_0.1Sn_0.5)O₃–yCa_0.8Sr_0.2TiO₃ ceramic system shifted to higher angle as y increased. A dielectric constant of 41.2, a quality factor (Q × f) of 56,900 GHz, and a temperature coefficient of resonant frequency of ?6 ppm/ °C were obtained when the 0.4La(Mg_0.4Sr_0.1Sn_0.5)O₃–0.6Ca_0.8Sr_0.2TiO₃ ceramic system was sintered at 1,550 °C for 4 h.     

Effect of preparation methods on microstructures and microwave dielectric properties of Ba(Mg1/3Nb2/3)O3 ceramics

Effect of preparation methods on microstructures and microwave dielectric properties of Ba(Mg_1/3Nb_2/3)O₃ ceramics was investigated. Ba(Mg_1/3Nb_2/3)O₃(BMN) ceramics were prepared by the conventional mixed oxides method and the molten salt synthesis method. It was shown that the single-phase of BMN was obtained at 900 °C in the molten salt synthesis method. No single-phase BMN was obtained in the conventional mixed oxides method, although the calcining temperature was increased up to 1400 °C. BMN powders prepared by the molten salt synthesis method had better sinterability than that prepared by the conventional mixed oxides method. Because of the very different nature of the powders, different microstructures were observed. The molten salt synthesis method ceramics have a higher B-site ordering parameter (S) and larger grain size than that of the conventional mixed oxides ceramics at same sintering temperature. The variation of Qf, ε _r and τ _f were also explained based on the difference in microstructures.     

Structure and microwave dielectric characteristics of lithium-excess Ca0.6Nd0.8/3TiO3/(Li0.5Nd0.5)TiO3 ceramics

Compositions based on (1−x)Ca_0.6Nd_8/3TiO₃−x(Li_1/2Nd_1/2)TiO₃ + yLi (CNLNTx + yLi, x = 0.30–0.60, y = 0–0.05), suitable for microwave applications have been developed by systematically adding excess lithium in order to tune the microwave dielectric properties and lower sintering temperature. Addition of 0.03 excess-Li simultaneously reduced the sintering temperature and improved the relative density of sintered CNLNTx ceramics. The excess Li addition can compensate the evaporation of Li during sintering process and decrease the secondary phase content. The CNLNTx (x = 0.45) ceramics with 0.03 Li excess sintered at 1190 °C have single phase orthorhombic perovskite structure, together with the optimum combination of microwave dielectric properties of ɛ_r = 129, Q × f = 3600 GHz, τ_f = 38 ppm/°C. Obviously, excess-Li addition can efficiently decrease the sintering temperature and improve the microwave dielectric properties. The high permittivity and relatively low sintering temperatures of lithium-excess Ca_0.6Nd_0.8/3TiO₃/(Li_0.5Nd_0.5)TiO₃ ceramics are ideal for the development of low cost ultra-small dielectric loaded antenna.     

Influence of SrTiO3 modification on dielectric properties of Mg(Zr0.05Ti0.95)O3 ceramics at microwave frequency

The microwave dielectric properties and microstructures were investigated in the (1?x)Mg(Zr_0.05Ti_0.95)O₃–xSrTiO₃ (hereafter referred to as (1?x)MZT–xST) system. The compounds were prepared via the conventional solid-state reaction. Compositions in the (1?x)Mg(Zr_0.05Ti_0.95)O₃–xSrTiO₃ system were designed to compensate the negative temperature coefficient of the resonant frequency of Mg(Zr_0.05Ti_0.95)O₃. The values displayed nonmonotonic mixture-like behavior, because the TiO₂ phase was formed in the MZT composite ceramics with increasing x. A close zero τ_f of 0.2 ppm/°C could be achieved at 0.96MZT–0.04ST with ?_r = 20.8 and Q × f = 257,000 GHz.     

Effect of B2O3 additive on the sintering temperature and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 ceramics

Journal of Materials Science: Materials in Electronics - This paper reported a research of the sinterability, microstructures, and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 (BMT) ceramics...     

Microwave dielectric properties of Mg(Zr0.05Ti0.95)O3-SrTiO3 ceramics

The microwave dielectric properties of (1−x)Mg(Zr_0.05Ti_0.95)O₃-xSrTiO₃ ceramics prepared by conventional solid processing were investigated. With increasing x, the dielectric constant and the quality factor decreased, and the temperature coefficient of resonant frequency was tuned from negative to positive value. The effect of sintering temperature on microwave properties was also studied. After sintering at 1,390 °C for 4 h, the ceramics exhibited a near zero temperature coefficient of resonant frequency about 2.1 ppm/°C, an optimum dielectric constant of 20.9 and a high quality factor of 203000 (6.8 GHz), at the level of x = 0.05.     

Effect of nickel on microwave dielectric properties of Ba(Mg1/3Ta2/3)O3

The dielectric and physical properties of the complex perovskite Ba(Mg_1/3Ta_2/3)O₃ system in which magnesium was substituted for nickel from 0.03–0.67 mol%, were investigated in the temperature range 20–110C, and the frequency range 10.5–14.5 GHz. As the nickel content was increased, the dielectric constant, the degree of ordering, and the unloaded Q decreased. The temperature dependence of the dielectric constant and the temperature coefficient of resonant frequency of the specimens annealed at 1500C for 20 h were found to be greater than those of the specimens sintered at 1650C for 2 h. These results are due to the increase in the density, the increase in grain size, and the lattice distortion.     

Formation and microwave dielectric properties of Sr(Ga0.5Ta0.5)O3-based complex perovskites

The Sr(Ga0.5Ta0.5)O3-based perovskites with O2- and/or Sr2+ vacancies were formed by changing the A-site and/or B-site cation ratios. The Sr-deficient perovskites with a limited composition of Sr0.86(Ga0.36Ta0.64)O3 could be obtained, whereas oxygen vacancies were hardly created. The B′-site Ga3+ cation could be replaced with large Sc3+, In3+, Y3+, Nd3+ and La3+. The crystal symmetry of the complex perovskites changed from cubic (B′=Ga3+, Sc3+, In3+) to tetragonal (B′=La3+) through rhombohedral (B′=Y3+, Nd3+). The dielectric permittivities of these ceramics indicated no distinct dependence on the B′-site cation species. The temperature coefficient of permittivity might be associated with the symmetry change of the perovskite phases. Higher microwave Qf values, >Qf=38 000 GHz, were obtained for our complex perovskite ceramics, except with B′=La3+. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Sm3+ ions on structural, dielectric, and electrical properties of Pb(SnTi)O3 ceramics

Powders and pellets of (Pb_1–x Sm _x )(Sn _y Ti_1–y )_1–x/4O₃ (PSmST) ferroelectric ceramics with x=0, 0.05, 0.07, 0.1 and y=0.45 have been synthesized using a solid-state reaction technique. Preliminary studies of X-ray diffraction (XRD) patterns and scanning electron microscopic images of these compounds at room temperature suggest that compounds formed in a single phase with the orthorhombic crystal system and a uniform grain distribution throughout the surface of the samples. Dielectric study of these compounds as a function of temperature suggests that with increase in concentration of Sm³⁺, the relative dielectric constant maximum decreases. The electrical conductivities (a.c. and d.c.) of the PSmST compounds have been investigated and the activation energies (E_a.c. and E_d.c.) have also been calculated. It is observed that for each concentration of Sm the relative dielectric constant () reaches its maximum value at the same transition temperature for all the three frequencies, which reveals the non-relaxor ferroelectric behavior of the materials.     

低损耗( Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4陶瓷的微波介电性能研究

采用标准电子陶瓷工艺制备了(Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4陶瓷.研究了(Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4陶瓷的烧结特性、相结构和微波介电性能.采用X射线衍射分析其物相组成,利用SEM观察其显微结构.XRD图谱表明烧结样品为立方尖晶石( Mg0.95Zn0.05)2(Ti...