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Tri‐layer ZnZrNb1.99(Sn0.5W0.5)0.01O8–TiO2–ZnZrNb1.99(Sn0.5W0.5)0.01O8 and random distribution ZnZrNb1.99(Sn0.5W0.5)0.01O8@TiO2 ceramics with different mass fractions of TiO2 were initially synthesized. The effects of the laminated cofiring and the random distribution processes on the crystal structure and microwave dielectric properties of the composite ceramics were investigated. The advantages of the unique tri‐layer architecture were fully demonstrated. It not only allows the effects of the chemical reactions between ZnZrNb1.99(Sn0.5W0.5)0.01O8 and TiO2 can be effectively limited to a narrow region (∼20 μm in width) within the ZnZrNb1.99(Sn0.5W0.5)0.01O8/TiO2 interfaces, and acts as the "glues" to bond each layer well. The layers are well connected and the possibility of deterioration of Q× f values during the modification process can be greatly reduced. When compared with ZnZrNb1.99(Sn0.5W0.5)0.01O8@TiO2 ceramics with random distribution type, the tri‐layer design can produce a roughly 60% improvement in Q× f value with no noticeable loss in dielectric constant while maintaining temperature stability. After sintering at 1340°C for 6 h, ZnZrNb1.99(Sn0.5W0.5)0.01O8–TiO2–ZnZrNb1.99(Sn0.5W0.5)0.01O8 tri‐layer ceramics exhibited excellent dielectric properties (εr = 30.29, Q× f = 56,880 GHz, and τf = −5.73 ppm/°C) with 0.05 wt% TiO2, and the cooperative optimization of microwave dielectric properties was achieved. The current research provides a strategy for synthesizing microwave dielectric devices with high dielectric properties for applications in 5G network communications. [ABSTRACT FROM AUTHOR]

The ZnZrNb2O8 + x wt% LiF, MgF2, CuO (0.00 ≤ x ≤ 0.10), and Zn1−xCuxZrNb2O8 (0.000 ≤ x ≤ 0.050) ceramics were synthesized through solid‐state reaction. Compared with pure ZnZrNb2O8 ceramic, the quality factor and microstructure densification of the specimens with the addition of trace additives were significantly improved. When CuO was utilized as a sintering additive, εr${\varepsilon _r}$ is mostly impacted by relative density, whereas Q×$ \times \;$f value is primarily influenced by grain size. When CuO was employed as a dopant, εr${\varepsilon _r}$ is strongly connected to the dielectric polarizability and lattice vibration, Q×$ \times \;$f value is driven mostly by chemical bond covalency, and τf${\tau _f}$ value is primarily dictated by variations in Nb–O bond energy and bond valence. Notably, the ceramics demonstrated excellent characteristics (εr${\varepsilon _r}$ = 27.404, Q×$ \times \;$f = 74 213 GHz, τf${\tau _f}$ = −52.779 ppm/°C, ZnZrNb2O8 + 0.06 wt% CuO; εr${\varepsilon _r}\;$= 27.448, Q×$\; \times $ f = 72 520 GHz, τf${\tau _f}\;$= −53.143 ppm/°C,Zn0.997Cu0.003ZrNb2O8), and these make them promising for use in fifth generation communications. [ABSTRACT FROM AUTHOR]

Strain and stress play an important role in functional materials, but they are often neglected in electroceramics. Here we report the stress effect on microwave dielectric loss in rutile-related (Ti 0.6 Zr 0.4) 0.8 (Zn 1/3 Nb 2/3) 0.2 O 2 solid solutions. The macroscopic, microscopic and nano-scale residual stresses have been systematically investigated, including their relationships. The average Raman spectra have demonstrated considerable macro-residual stresses, especially for the heavily cracked sample. The high-resolution Raman images reveal the inhomogeneity of residual stress distribution at the grain-level, which is reflected by the shifts of Raman-active modes. The high-resolution transmission electron microscope (HRTEM) images and geometric phase analysis (GPA) analysis show the aggregation of dislocations and resulting distortion of crystal. It can be found that the dielectric loss depends strongly on residual stresses, that samples with greater residual stress exhibit much higher dielectric loss because the residual stress increases the vibration anharmonicity of the lattice. [ABSTRACT FROM AUTHOR]

MgNb 2-x V x/2 O 6-1.25x (0.1≤x≤0.6) ceramics with orthorhombic columbite structures were prepared at low-temperature by a solid-phase process. The phase component, microscopic morphology, low-temperature sintering mechanism and microwave dielectric performance of MgNb 2-x V x/2 O 6-1.25x ceramics were comprehensively investigated. Low-temperature sintering densification of dielectric ceramics was achieved via the nonstoichiometric substitution of vanadium (V) at the Nb-site. In contrast to pure MgNb 2 O 6 ceramics, the sintering temperature of MgNb 2-x V x/2 O 6-1.25x (x = 0.2) ceramics was reduced by nearly 300 °C owing to the liquid-phase assisted sintering mechanism. The liquid phase arises from the autogenous low-melting-point phase. Meanwhile, MgNb 2-x V x/2 O 6-1.25x (x = 0.2) samples with nonstoichiometric substitution could achieve a more than 900% improvement in the Q × f value, compared with stoichiometrically MgNb 2-x V x O 6 (x = 0.1, 0.2) ceramics. Finally, MgNb 2-x V x/2 O 6-1.25x dielectric ceramics possess outstanding microwave dielectric properties: ε r = 20.5, Q × f = 91000, and τ f = -65 ppm/°C when sintered at 1030 °C for x = 0.2, which provides an alternative material for LTCC technology and an effective approach for low-temperature sintering of Nb-based microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

Recently, the progress of miniaturization and integration for dielectric communication devices is being motivated by the rapidly‐developed communication technology. Microwave dielectric ceramics, the foundation of dielectric communication devices, have been receiving great attention. In this study, 0.91MgTiO3‐0.09(Ca0.8Na0.1Ce0.1)TiO3 ceramic (0.91MT‐0.09CNCT) was synthesized by the traditional solid‐phase process to tune the temperature coefficient of resonant frequency (τf) to zero. Compared with 0.95MgTiO3–0.05CaTiO3 ceramic, a Q×f value increased by 15 % was achieved in 0.91MT‐0.09CNCT ceramic, meanwhile, the sintering temperature of which was significantly lowered by 225 °C. In general, the τf value is related to the (Ca0.8Na0.1Ce0.1)TiO3 content and sintering temperature. At the same time, the 0.91MT‐0.09CNCT ceramic sintered at 1175 °C has competitive dielectric properties: ϵr=20.4, Q×f=66,000 GHz, τf=0.2 ppm/°C, which suggests it a promising candidate for dielectric communication devices with low cost and green synthesis. [ABSTRACT FROM AUTHOR]

As a common flux agent, B 2 O 3 –CuO was introduced into Li 2 TiO 3 system to reduce the sintering temperature for the requirements of LTCC applications. The optimal mass ratio of CuO to B 2 O 3 was innovatively explored. When the mass ratio of CuO to B 2 O 3 increased to 1.2:1.0, excellent microwave dielectric properties were obtained in LTMF&LTZN 0.892 +CB 1.2 ceramic of ε r = 13.23, Q × f = 62,749 GHz, τ f = -2.48 ppm/°C and the sintering temperature was reduced from 1300 to 930 °C. In a wide temperature range, the sample still maintain high temperature stability of |τ f | < 5 ppm/°C (-40–120 °C). Based on the LTMF&LTZN 0.892 +CB 1.2 substrate, a millimeter wave microstrip antenna resonated at 30.12 GHz was designed with a considerably high radiation efficiency of 93.94% and a signal gain of 4.87 dB. Comprehensive microwave dielectric properties make LTMF&LTZN 0.892 +CB 1.2 become a candidate material for LTCC applications. [ABSTRACT FROM AUTHOR]

Microwave ceramic with ultra-high Q value is one of the most significant classes of material to realize the miniaturization and integration of microwave devices. In this paper, to improve the microwave dielectric properties of ceramics, MgTiO 3 - x wt.% MgF 2 (x = 0, 3, 4, 5, and 6) microwave ceramics with high-quality factor were synthesized by solid-state reaction method. The effects of MgF 2 addition on the phase composition, sintering behavior, and microwave dielectric properties of MgTiO 3 were investigated. In comparison to pure MgTiO 3 , our study demonstrates that the Q × f values can be dramatically enhanced with the doping of MgF 2. After being sintered at 1300 °C for 4 h, the MgTiO 3 -3 wt.% MgF 2 showed the best microwave dielectric properties of ε r ∼18.09, Q × f ∼262,900 GHz (at 8.98 GHz) and τ f ∼ −41.5 ppm/°C. The outstanding performance of MgF 2 doped MgTiO 3 ceramics provides a solid foundation for widespread applications of microwave dielectric substrates, resonators, filters and patch antennas in modern wireless communication equipment. • Mg 2 TiO 4 phase of ceramics were analyzed based on RP phase. • The leakage current was analyzed based on the grain boundary barrier effect. • The bulk density at different sintering temperatures were analyzed. • The optimum densification sintering process was determined. [ABSTRACT FROM AUTHOR]

To determine the mechanism of microwave response in AZrNb 2 O 8 (A: Mn, Zn, Mg, Co, et al.) wolframites, CuZrNb 2 O 8 ceramic with low sintering temperature (920 °C) is successfully fabricated by solid-state reaction method. Meanwhile, its structural stability is synthetically evaluated, the vibration modes are also calibrated. Except for the extrinsic factor like sintering temperature, the condition of Jahn-Teller ion Cu2+ as intrinsic part is characterized for the first time in relation to the microwave dielectric properties of the system. In virtue of Raman and EPR spectra, it is predicted that the electronic structure of transition metal ions, as the less concerned factor, may be influential on the dielectric properties of ceramics at microwave range, especially in the structure with mixed ion occupancy. In addition, the CuZrNb 2 O 8 ceramic is well matched with the silver electrode, which makes it a prospective candidate for temperature compensation material of LTCC (low-temperature co-fired ceramic) passive integration technology. [ABSTRACT FROM AUTHOR]

Preliminary tri-layer architecture ZnNb 1.8 V 0.1 O 5.75 -TiO 2 +CuO–ZnNb 1.8 V 0.1 O 5.75 ceramics with high-temperature stability and low dielectric loss have been prepared. In the past, the stacked co-firing process could only be used at normal sintering temperatures. In this paper, the effect of the transition layer in ZnNb 1.8 V 0.1 O 5.75 -TiO 2 +CuO–ZnNb 1.8 V 0.1 O 5.75 ceramics with tri-layer architecture sintered at low temperatures (950 °C) on the crystalline structure, microscopic structure, and integrated microwave dielectric performance of specimens has been investigated in depth for the first time. This low-temperature stacked-layer co-firing technique can effectively enable the chemical reaction between ZnNb 1.8 V 0.1 O 5.75 and TiO 2 +CuO to take place in a rather narrow region (about 20 μm), i.e., the interface of the heterogeneous layers. In this interface, diffusion of Zn, Nb, V, Ti, and Cu can be observed. This heterogeneous interface can act as an in-situ "glue" that holds the layers together well. The effect of TiO 2 +CuO content on the microwave dielectric performances of laminated architectural specimens under low-temperature sintering was systematically investigated. Among the existing layer architectures, the stack of ZnNb 1.8 V 0.1 O 5.75 -TiO 2 +CuO–ZnNb 1.8 V 0.1 O 5.75 with 0.03 wt% TiO 2 +CuO exhibits the most excellent microwave dielectric performances. τ f can be efficiently tuned close to zero (−7.14 ppm/°C), and remarkably, a low dielectric loss (14,587 GHz) and a high value of ε r (24.00) are also achieved. This low-temperature sintered tri-layered architecture is designed to help open new avenues for the development of high-performance microwave dielectrics based on existing material systems, providing effective strategies and methods for 5G applications and multilayer packaging technologies. [ABSTRACT FROM AUTHOR]

Abstract LiZn 1-x M x NbO 4 (M = Co, Ni) (x = 0–0.06) systems were fabricated by a facile solid-state reaction method. Structure and property relationships of spinel structured LiZn 1-x M x NbO 4 were investigated systematically. Appropriate amount of Co2+ and Ni2+ greatly improved the dielectric loss of LiZnNbO 4 ceramics. While, the dielectric loss deteriorated seriously when the doping content exceeded x = 0.02. The origin of dielectric loss in LiZn 1-x M x NbO 4 ceramics was investigated systematically. Moreover, the theoretical dielectric constant and linear expansion coefficient were calculated on the bases of the crystallographic parameters from XRD refinement. The temperature coefficient of resonant frequency calculated by the P-V theory agreed well with the test values. Due to the small doping content, the change in chemical bonds was negligible. Density became the major factor determining the variation of dielectric constant in LiZnNbO 4 ceramics. At last, excellent microwave dielectric properties were obtained: Ts = 1010 °C, ε r = 15.25, Q f = 107,000 GHz, τ f = −63.3 ppm/°C for LiZn 0.98 Co 0.02 NbO 4 and Ts = 995 °C, ε r = 14.85, Q f = 104,000 GHz, τ f = −61.7 ppm/°C for LiZn 0.98 Ni 0.02 NbO 4. Highlights • Structure and property of spinel structured LiZn 1-x M x NbO 4 are investigated. • The origin of dielectric loss in LiZn 1-x M x NbO 4 ceramics is clarified. • Dielectric constant and linear expansion coefficient are obtained by the P-V theory. • Excellent microwave performance make it a promising candidate for LTCC applications. [ABSTRACT FROM AUTHOR]

Inequivalent La 3+ is firstly utilized to modify the microwave dielectric properties in SrTiO 3 ceramic system. For the general composition of Sr 1-x La 2x/3 TiO 3 (0 ≤ x ≤ 1), the effects of La 3+ introduction on the phase transition and structural changes are systematically investigated. The correlation between A-site ordering degree and dielectric loss in microwave range is established, and the temperature coefficient of resonant frequency is also dramatically improved. When x = 0.945, excellent dielectric properties of ε r ∼89.3, Qf ∼15243 GHz (@4.3 GHz) and τ f  ∼ 160 ppm/°C are obtained, making it potential to meet the application requirements of 5G technologies. [ABSTRACT FROM AUTHOR]

Low-loss (Zn 1- x Ni x )ZrNbTaO 8 (0.02 ≤  x  ≤ 0.10) ceramics possessing single wolframite structure are initiatively synthesized by solid-state route. Based on the results of Rietveld refinement, complex chemical bond theory is used to establish the correlation between structural characteristics and microwave performance in this ceramic system. A small amount of Ni 2+ ( x  = 0.06) in A-site with the fixed substitution of Ta 5+ in B-site can effectually raise the Q  ×  f value of ZnZrNb 2 O 8 ceramic, embodying a dense microstructure and high lattice energy. The dielectric constant and τ f are mainly affected by bond ionicity and the average octahedral distortion. The (Zn 0.94 Ni 0.06 )ZrNbTaO 8 ceramic sample sintered at 1150 °C for 3 h exhibits an outstanding combination of microwave dielectric properties: ε r = 27.88, Q × f  = 128,951 GHz, τ f = –39.9 ppm/°C. Thus, it is considered to be a candidate material for the communication device applications at high frequency. [ABSTRACT FROM AUTHOR]

The effects of TiO 2 doping on the phase transition and microwave dielectric performances of ZnNb 1.8 V 0.1 O 5.75 @xTiO 2 (0.05 ≤ x ≤ 0.60) ceramics prepared by conventional mixing methods were investigated. In this study, we report for the first time the phase transition of ZnNb 2 O 6 with columbite structure at low temperature (950 °C) where the τ f value is adjusted to near zero. With the increase of TiO 2 doping, the following phase transitions are experienced in the ceramics: columbite + monoclinic → columbite + monoclinic + ixiolite → monoclinic + ixiolite → monoclinic + ixiolite + rutile. The microscopic morphology of ceramics is greatly influenced by TiO 2 doping. The grain size of ceramics continues to grow as TiO 2 doping increases. The microwave dielectric performances of ceramics are intimately connected to the phase transition process, which occurs when the Q × f value constantly declines while the τ f value steadily increases and is adjusted to near zero at x = 0.50. After sintering at 950 °C for 6 h, the most optimal microwave dielectric performances were obtained for x = 0.50 with a dielectric constant of 41.18, a Q × f value of 6852 GHz, and a τ f value of +6.83 ppm/°C, providing a new option with great potential for microwave devices requiring medium dielectric ceramics. [ABSTRACT FROM AUTHOR]

The ZnNb 2-x V x/2 O 6-1.25x (0.1 ≤ x ≤ 0.6) dielectric ceramics were synthesized through conventional solid-state technique and sintered at 925 °C–975 °C for 6 h. The specimens with the substitution of V5+ for Nb5+ could be sintered at a lower temperature than pure ZnNb 2 O 6 ceramic, densifying the microstructure more densely and improving the quality factor. Density analysis proves that the dielectric constant is related to the relative density. In addition, the [NbO 6 ] octahedral distortion, the bond valence and the average bond energy of the Nb–O bond also change, leading to a nonlinear variation for the temperature coefficient of the resonance frequency from x = 0.1 to 0.6. The ZnNb 2-x V x/2 O 6-1.25x (x = 0.2) ceramics sintered at 950 °C exhibited the superior characteristic while taking into account the applications of low temperature co-fired ceramics technology. Not only did it possesses outstanding dielectric performances of ε r = 22.25, Q × f = 51,701 GHz, and τ f = −67.02 ppm/°C, but also has excellent chemical compatibility with the widely used Ag electrode. [ABSTRACT FROM AUTHOR]

The phase composition, crystal structure and microwave dielectric properties of (1-x) (3ZnO-Nb 2 O 5 )-xGeO 2 were investigated systematically. The phase composition and phase transformation of (1-x) (3ZnO-Nb 2 O 5 )-xGeO 2 ceramics were confirmed by XRD refinement, SEM micrographs and EDS analysis. All sintered samples were composed of Zn 3 Nb 2 O 8 and ZnNb 2 O 6 phases. Phase transition between Zn 3 Nb 2 O 8 and ZnNb 2 O 6 was closely related the introduction of GeO 2 . When the doping content was low (x = 0–0.007), the phase transformation from ZnNb 2 O 6 to Zn 3 Nb 2 O 8 occurred, which was discovered for the first time. To clarify the phase transition, the local charge density and band structures were calculated using the CASTEP program. With the substitution of Ge 4+ , part of the electrons transferred from the oxygen atom to the middle of 'niobium-oxygen' and 'zinc-oxygen'. According, the covalency of 'niobium-oxygen' and 'zinc-oxygen' was enhanced. The shrinkage of ZnO 6 octahedron resulted in a decrease in the coordination number of zinc atoms. At last, the relationships between phase transition, crystal structure and the microwave performance were established. The system of 2.73ZnO-0.91Nb 2 O 5 -0.09GeO 2 sintered at 1150 °C for 6 h had excellent microwave dielectric properties: ε r  = 21.3, Q f  = 99,140 GHz, τ f  = −54 ppm/°C, which, to our best knowledge, the best performance with relative lower sintering temperature. [ABSTRACT FROM AUTHOR]

Abstract: Al/Nb co‐doped SrTiO3 microwave ceramics with the composition of SrTi1–x(Al0.5Nb0.5)xO3 (x = 0.03, 0.05, 0.1, and 0.15) have been synthesized via a standard solid‐state reaction method. The substitution of (Al0.5Nb0.5)4+ in B‐site inhibits the reduction in Ti4+ ions and the growth of grain size, then the transport of mobile charge carriers is limited, and thus the Q value is improved. For the SrTi0.9(Al0.5Nb0.5)0.1O3 ceramics, in addition to their high dielectric constant (εr ~185), they exhibit correspondingly a high Qf value (~ 9077 GHz) at 2.9 GHz, making the microwave ceramics suitable for myriad device miniaturization and high‐performance wireless communication. [ABSTRACT FROM AUTHOR]

The ZnZrNb 2-x V x/2 O 8-1.25x -based (0.2 ≤ x ≤ 0.6) ceramics with monoclinic wolframite structure were prepared by the solid-phase method at low temperature. The microscopic morphology, phase structure, low-temperature sintering mechanism, and microwave dielectric performances of ZnZrNb 2-x V x/2 O 8-1.25x -based (0.2 ≤ x ≤ 0.6) ceramics were thoroughly analyzed. Low-temperature sintering densification of microwave dielectric ceramics was made achievable by substituting non-dense vanadium at the Nb location. The sintering temperature of ZnZrNb 2-x V x/2 O 8-1.25x (x = 0.4) ceramics was reduced by 340 °C when compared to pure ZnZrNb 2 O 8 ceramics due to the mechanism of liquid phase aided sintering. The self-generated low melting point phase forms a liquid phase during the sintering process reducing the sintering temperature. It is noteworthy that when sintered at 900 °C, the ZnZrNb 2-x V x/2 O 8-1.25x (x = 0.4) ceramic exhibits extremely exceptional microwave dielectric performances: ε r = 25.15, Q × f = 17,600 GHz (at 8.01 GHz), and τ f = −53.25 ppm/°C. The proposed material configuration provides a candidate material with extremely broad application potential for LTCC applications and a practical and effective strategy for low-temperature sintering of Nb-based monoclinic wolframite structured microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

Spinel CoZnTiO ceramics were synthesized by conventional solid-state method and their microwave dielectric properties were investigated. The crystal structure and microstructures of specimens were studied by XRD and SEM. The CoZnTiO phase forms at a temperatures ranging from 1140 to 1220 °C and the dependence of the dielectric properties of the ceramics on the sintering condition is found to be insignificant. The relative densities of the specimens are higher than 95 % for the entire temperature range tested during the experiment. Specimen using CoZnTiO sintered at 1200 °C possesses a combination of dielectric properties with ε ~ 17.31, Q × f ~ 97,571 GHz (where f = 8.84 GHz, is the resonant frequency) and τ ~ −36.4 ppm/°C, which makes it a suitable candidate material for microwave devices. [ABSTRACT FROM AUTHOR]

The (ZnCo)ZrNbO (x = 0.1, 0.2, 0.3, 0.4) ceramics were synthesized by the conventional solid-state reaction route and sintered in the temperature range of 1160-1320 °C. The microstructure and microwave dielectric properties were investigated systematically. The X-ray diffraction results showed that the (ZnCo)ZrNbO ceramics exhibited a single monoclinic structure. The variation trend of dielectric constant ( ε) was in accordance with variation trend of relative density. The Qf value decreased with the decrease of the packing fraction. The temperature coefficient of resonant frequency (τ) moved towards positive due to the increase of B-site bond valence. In conclusion, the excellent microwave dielectric properties were obtained for ZnCoZrNbO ceramics sintered at 1240 °C for 4 h: ε = 27.93, Q × f = 68,615 GHz (where f = 6.95 GHz), and τ = −61.94 × 10/°C. [ABSTRACT FROM AUTHOR]

A high quality microwave dielectric material Mg 0.5 Zn 0.5 ZrNb 2 O 8 was reported in this paper. Single-phase Mg 0.5 Zn 0.5 ZrNb 2 O 8 was prepared by a conventional mixed-oxide route and sintered in the temperature range of 1220−1300 °C. The microstructure and microwave dielectric properties were investigated systematically. The X-ray diffraction results showed that all samples exhibit a single monoclinic structure. The variation trend of dielectric constant was in accordance with that of relative density. The Q f value mainly depended on the crystal structure, and it increased with the increasing packing fraction. The temperature coefficient of τ f correlated with the variation of bond valence of B-site. In summary, the monoclinic structure Mg 0.5 Zn 0.5 ZrNb 2 O 8 ceramic samples sintered at 1260 °C exhibited uniform and dense microstructural morphology, and owned outstanding microwave dielectric properties of ε =27.06, Q f =91077 GHz, τ f =−18×10 −6 /°C. These represent very promising candidates for the application of highly selective microwave ceramic resonators and filters. [ABSTRACT FROM AUTHOR]

Cubic pyrochlore Bi 1.5 Mg 1.0 Nb 1.5 O 7 (BMN) thin films were prepared on substrates including amorphous glass, mono-crystal silicon and poly-crystal Ba(Mg 1/3 Nb 2/3 )O 3 ceramic by sol–gel technique with rapid thermal annealing (RTA). The effects of different substrates on the structures and microwave dielectric properties were investigated. The results showed that the BMN thin film deposited on the Si(1 0 0) exhibited best crystallinity and highest dielectric constant, with strong (2 2 2) orientation. While the glass and ceramic samples presented relative lower crystallinity and dielectric constant, with a slightly (2 2 2) and (4 0 0) orientations, respectively. Dielectric relaxation was observed in the film on ceramic substrate in the microwave frequency region. It was found that the crystalline structures were remarkably influenced by the type of the substrates, which was mainly due to the thermal mismatch between the films and the substrates. The substrate-dependence of the microwave dielectric properties in the BMN thin films was attributed to the combined effects of crystallinity, orientation and thermal strain. [ABSTRACT FROM AUTHOR]

The microstructures and microwave dielectric properties of Zn-excess (0.0 mol%, 0.5 mol%, 1.0 mol%, 2.0 mol%, 3.0 mol%) Mg 0.97 Zn 0.03 TiO 3 ceramics prepared via the conventional solid-state reaction route were investigated. With Zn-excess doped, the sintering temperature of the specimens can be slightly reduced from 1275 °C to 1250 °C. Microwave dielectric properties of the compounds were studied systematically. A slight Zn-excess does not have obvious effect on the relative dielectric constant ( ε r ) and temperature coefficient of resonant frequency ( τ f ) of the specimens. However, the Q × f is very sensitive to the amount of Zn-excess. As the content of Zn-excess increased, the MgTi 2 O 5 phase which was derived from sample without Zn-excess disappeared. Along with the augmentation of Zn-excess, the Q × f , bulk density and ε r show an initial increase, followed by a decrease, but the last two factors do not change much. An extremely high Q × f of 277,500 GHz (at 8.5 GHz) together with an ε r of 17.66 and a τ f of −55.09 × 10 −6 /°C can be found for Mg 0.97 Zn 0.03 TiO 3 specimen with 0.5 mol% Zn-excess sintered at 1250 °C for 4 h. [ABSTRACT FROM AUTHOR]

• Raman mapping technique is used to investigate residual stress. • The two-step sintering is developed to improve the Q × f value. • High Q × f value materials are prepared in air without sintering aids. (Mg 1/3 Nb 2/3) x (Zr 0.4 Ti 0.6) 1-x O 2 (x = 0.05–0.15) ceramics are fabricated by solid-state reaction methods. With the increase of x value, the phase content and microwave dielectric loss change significantly. The Raman mapping technique is used to investigate the residual stresses and the anharmonic vibration of phonons. It is proved that the volume variation caused by the first-order phase transition will lead to non-uniform internal stress and lattice anharmonicity. Moreover, for the x = 0.12 sample with near zero τ f , the two-step sintering is conducted to reduce residual stresses and improve the Q × f value. The optimized microwave dielectric properties with τ f ∼ 1.23 ppm/°C, ɛ r ∼ 40.7 and Q × f ∼ 41461 GHz are obtained by two-step sintering, while the Q × f value is about 5 times that of the normal sintering sample. [ABSTRACT FROM AUTHOR]

Highlights: [•] The crystal structure of Ca x Zn1 − x Sn0.08Ti1.92Nb2O10 ceramics were analyzed. [•] The quantitative determination of Ca x Zn1−xSn0.08Ti1.92Nb2O10 ceramics were analyzed. [•] The typical values of ε =53.09, Qf =48,000GHz, τf =21.20ppm/°C were obtained. [ABSTRACT FROM AUTHOR]

To address the nonlinear variation of resonant frequency in a MgTiO 3 -CaTiO 3 system over a wide temperature range (-40–105°C), MgTiO 3 -Li 2 TiO 3 system ceramics with multilayer architectures are designed. Trilayer MgTiO 3 -Li 2 TiO 3 -MgTiO 3 ceramics (mass ratio=0.2:0.56:0.2) sintered at 1275°C possess a linear and near-zero temperature coefficient of resonant frequency (τ f+ =-3.0 ppm/°C (25–105°C), τ f- =2.7 ppm/°C (-40–25°C)). Compared with that of random distribution-type MgTiO 3 -Li 2 TiO 3 ceramics, the Q × f value of trilayer ceramics is significantly improved (Q × f =80,000 GHz (@7.6 GHz)). The electric field distribution is examined by the eigenmode solver of High Frequency Structure Simulator software to analyze the effect of the Li 2 TiO 3 content and the stacking scheme on the dielectric properties. The cross-sectional morphologies show a dense intermediate layer formed by ion diffusion, which acts as a glue to bond each layer. This work can be conceived as a new strategy for developing 5G wireless communication components with linear temperature-related resonant frequency (-40–105°C) and low dielectric loss. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Composite dielectrics, (1− y)(Mg1−x Zn x )1.8Ti1.1O4–yCaTiO3, were prepared by the conventional solid-state route. The results of the X-ray diffraction and field emission scanning electron microscopy (FESEM) indicated the formation of solid solutions. Microwave dielectric properties of the composites were investigated systematically. For (Mg1−x Zn x )1.8Ti1.1O4 system, superior dielectric properties (ɛ r =15.03, Q × f =185,000GHz, τ f =−45.1 × 10−6/°C) were achieved with (Mg0.95Zn0.05)1.8Ti1.1O4 sintered at 1375°C. CaTiO3, as a τ f compensator, was added to form a temperature-stable ceramic system. For (1− y)(Mg0.95Zn0.05)1.8Ti1.1O4–yCaTiO3 system, 0.93(Mg0.95Zn0.05)1.8Ti1.1O4–0.07CaTiO3 ceramic sintered at 1375°C had optimal dielectric properties (ɛ r =18.26, Q × f =96,000GHz, τ f =−4.6 × 10−6/°C) which satisfied microwave applications in resonators, filters and antenna substrates. [Copyright &y& Elsevier]

Abstract: The crystal structure and microwave dielectric properties of Zn0.9Ti0.8−x Sn x Nb2.2O8 (x =0.00, 0.05, 0.10, 0.15) ceramics sintered at temperatures ranging from 1100°C to 1140°C for 6h were investigated. A single phase with ixiolite structure was obtained. With the increase of Sn content, the dielectric constant decreased attributed to the decrease of dielectric polarizability. The Qf value decreased with the decrease of packing fraction and grain size. The temperature coefficient of resonant frequency (τ f) increased due to the increase of the bond valence of Zn0.9Ti0.8−x Sn x Nb2.2O8 ceramics. The excellent microwave dielectric properties of ɛ =35.05, Qf=49,100GHz, τ f =−27.6×10−6/°C were obtained for Zn0.9Ti0.8−x Sn x Nb2.2O8 (x =0.05) specimens sintered at 1120°C for 6h. [Copyright &y& Elsevier]

Abstract: (Mg1−x Co x )TiO3 (x =0.00–0.09) ceramics were prepared by reaction sintering method. The correlations of crystal structure and the properties were analyzed on the basis of Rietveld refinement for specimens with different x. For x ≤0.5, solid solution phases with the ilmenite structure were obtained, which can be confirmed by the X-ray diffraction patterns and the lattice parameters measured. Whereas for x >0.05, secondary phase was detected besides the main phase. Dielectric properties were closely related with theoretical dielectric polarizabilities, packing fraction and average octahedral distortion. By increasing x from 0.00 to 0.09, the Q × f value of the specimen decreased from a maximum of 289,400GHz to 228,100GHz. A fine combination of microwave dielectric properties (ɛ r ∼16.1, Q × f ∼289,400GHz, τ f ∼−54.4×10−6/°C) was achieved for MgTiO3 ceramics sintered at 1350°C for 4h. [Copyright &y& Elsevier]

Abstract: The crystal structure and microwave dielectric properties of ZnTi(Nb1−x Ta x )2O8 ceramics were investigated. The ZnTi(Nb1−x Ta x )2O8 ceramics mainly contained ixiolite structure phase ZnTiNb2O8 and an unknown Columbite-type phase. The change of microwave dielectric properties was affected by the change of crystal structure of each phase. In ZnTi(Nb1−x Ta x )2O8 ceramics, the Columbite structure phase with increasing degree of ordering led to decrease of dielectric constant, increase of Qf, and to τf moving in the positive direction. The ZnTiNb2O8 with decreasing cation valence led to the increase of τf . The typical values were: ε = 34.05, Qf = 40,000 GHz, τf  = −66.07 ppm/°C. [Copyright &y& Elsevier]

The phase formation, microstructures and microwave dielectric properties of 0.5 wt% ZnO-doped 0.9MgTiO 3 –0.1(K 0.5 La 0.5 )TiO 3 ceramic system, prepared by conventional solid-state reaction route, were investigated, aiming to obtain a composite with low loss and nearly zero τ f value. Microwave dielectric properties were found strongly correlate with the densification and the second phase of the ceramic system. Moreover, doping with appropriate amount of ZnO as a sintering aid contributed to the enhancement of densification and microwave dielectric properties of the ceramic system. Excellent microwave dielectric properties ( ε r ~21.7, Q × f ~68,000 GHz (at 8 GHz) and τ f ~−0.7×10 −6 /°C) were achieved for 0.5 wt% ZnO-doped MgTiO 3 –(K 0.5 La 0.5 )TiO 3 ceramic system sintered at 1300 °C for 4 h. [ABSTRACT FROM AUTHOR]

Ceramics in the system MgO–SiO2–TiO2 were prepared by standard mixed oxide route. By adding ZnO–B2O3 to the starting mixtures, the firing temperature of the ceramics could be reduced to 1160 °C. Small additions of MnCO3 and CaTiO3 improve microwave dielectric properties leading to an increase in insulation resistance and a decrease in temperature coefficient of capacitance. By adding Co2O3 grain growth can be inhibited and the dielectric Qf value greatly increased. The resultant ceramic material exhibited low dielectric constant and low dielectric loss: relative permittivity (&epsiv;r): 20±2; temperature coefficient of capacitance (τc): 0±30 ppm/°C; Qf: 100,000 (at 10 GHz); insulation resistance: 1013 Ω cm: [Copyright &y& Elsevier]

With the development of 5G technology, millimeter wave communication has gradually attracted the attention of scholars. In order to meet the requirements of wireless communication for transmission rate, the research on millimeter wave microstrip antenna with wider frequency band and more stable gain is in full swing. Therefore, As the key material for microstrip antenna substrate, the performance of microwave dielectric ceramic plays a decisive role. Here, excellent performance microwave dielectric ceramics with low permittivity and high Q× f value were made by replacing Ti4+ of Li 2 Mg 3 TiO 6 (LMT) system with (Zn 1/3 Nb 2/3)4+. The phase composition, Raman spectra, micro-structure, bond valence, bond energy and microwave dielectric properties of Li 2 Mg 3 Ti 1-x (Zn 1/3 Nb 2/3) x O 6 (0.02 ≤ x ≤ 0.08) ceramics were investigated subsequently. Compared with pure LMT, all samples exhibited lower dielectric constant and higher Q× f value at the same time. In the range of 0.02 ≤ x ≤ 0.08, Li 2 Mg 3 Ti 0·92 (Zn 1/3 Nb 2/3) 0.08 O 6 ceramic sintered at 1285 °C exhibited the best microwave dielectric property of ε r ∼13.28, Q× f ∼168,911 GHz, τ f ∼ -42.88 ppm/°C. The ԑ r value of the system was decreased by 12.63%, and the Q× f value was increased by 11.13%, compared with pure LMT. Lower ԑ r value and higher Q× f value make Li 2 Mg 3 Ti 0·92 (Zn 1/3 Nb 2/3) 0.08 O 6 ceramic become an ideal material for preparing microstrip antennas. • The impact of (Zn 1/3 Nb 2/3)4+ in Li 2 Mg 3 Ti 1-x (Zn 1/3 Nb 2/3) x O 6 ceramics was explored. • Q× f value has increased by 11.13% in Li 2 Mg 3 Ti 0·92 (Zn 1/3 Nb 2/3) 0.08 O 6 ceramics. • ε r value has decreased by 12.63% in Li 2 Mg 3 Ti 0·92 (Zn 1/3 Nb 2/3) 0.08 O 6 ceramics. [ABSTRACT FROM AUTHOR]

With the deployment of 5G (5th generation wireless systems) worldwide, the development of dielectric duplexers more suitable for high-frequency applications is in full swing. Thus, the key material of dielectric duplexers, microwave dielectric ceramics, have attracted widespread attention from scholars. Here, high-performance microwave dielectric ceramics were prepared by adjusting the stoichiometry of Ta5+ of Ba(Mg 1/3 Ta x)O 3 within 0.67–0.68. Typically, excellent resonance frequency stability (resonance frequency offset is less than 1.2 MHz) in a wide temperature range (−55–85 °C) is obtained by all samples, which extends to the negative temperature range compared to previous studies. Optimally, the Ba(Mg 1/3 Ta 0.675)O 3 ceramic sintered at 1620 °C/12h and annealed at 1550 °C/10h is provided with the microwave dielectric properties of ε r ∼25.021, Q × f ∼244,155 GHz, τ f ∼ -0.74 ppm/°C, achieving an 11% increase in Q × f value (compared to pure BMT). Comprehensive and excellent performance makes Ba(Mg 1/3 Ta 0.675)O 3 ceramics furnish powerful material support for 5G dielectric duplexer applications. Image 1 • The impact of Ta5+ non-stoichiometry on Ba(Mg 1/3 Ta x)O 3 ceramics was explored. • Q × f value has been improved by 11% in Ba(Mg 1/3 Ta 0.675)O 3 ceramics. • Excellent temperature stability is obtained over a wide temperature range (−55–85 °C). [ABSTRACT FROM AUTHOR]

(Mg 1/3 Nb 2/3) x (Zr 0.5 Ti 0.5) 1-x O 2 (x = 0.00, 0.05, 0.10, 0.13, 0.15, and 0.20) systems without additives are fabricated by facile solid-state reaction method in the air atmosphere. The influence of (Mg 1/3 Nb 2/3)4+ substitution on microwave dielectric properties of (Mg 1/3 Nb 2/3) x (Zr 0.5 Ti 0.5) 1-x O 2 ceramics is investigated systematically. The XRD results convey that the doping ion ((Mg 1/3 Nb 2/3)4+) should occupy (Zr 0.5 Ti 0.5)4+ site throughout the composition. An appropriate amount of (Mg 1/3 Nb 2/3)4+ tremendously increases the temperature stability and reduces the microwave dielectric loss of the ZrTiO 4 ceramic. In addition, to further investigate the dielectric loss mechanism, high-resolution Raman mapping is used to characterize residual stresses at the grain level. The result justifies that there is non-uniform residual stress in the ceramic, which is closely related to the anharmonic vibrations of the crystal lattice and the intrinsic loss of (Mg 1/3 Nb 2/3) x (Zr 0.5 Ti 0.5) 1-x O 2 ceramics. Meanwhile, the annealing approach is applied for reducing the intrinsic loss and further improving the Q × f value. Ultimately, the optimum microwave dielectric properties with τ f ∼0.8 ppm/°C, high ϵ r ∼40.9 and Q × f ∼40,217 GHz are obtained in annealed (Mg 1/3 Nb 2/3) 0.13 (Zr 0.5 Ti 0.5) 0.87 O 2 ceramic, which suggests that it can be as one of the candidates exploiting for microwave devices in 5G wireless communication technology. [ABSTRACT FROM AUTHOR]

Tri-layered Zn 3 Nb 2 O 8 –TiO 2 –Zn 3 Nb 2 O 8 ceramic with high temperature stability are initially fabricated. On the basis of X-ray diffraction, Raman spectra and HFSS (High Frequency Structure Simulator) simulation, a reasonable parallel mode is put forward, then the transition layer at the heterogeneous interface is considered to be crucial to the microwave response in this system, and the theoretical feasibility of layer-cofired microwave dielectric ceramics is verified. Contrasting to the random distribution type Zn 3 Nb 2 O 8 –TiO 2 , this structure can substantially reduce the amount of TiO 2 and achieve an eightfold increase in Q f value, which is conducive to produce the new generation microwave passive devices. • Temperature-stable tri-layered Zn 3 Nb 2 O 8 –TiO 2 –Zn 3 Nb 2 O 8 ceramics are initially fabricated. • Compared to the random-type, an eightfold-increasing in Q f value can be achieved using this architecture. • A reasonable parallel mode is put forward to illustrate the microwave response in multi-layered ceramic system. [ABSTRACT FROM AUTHOR]

Tri-layer ZnTi 0.97 Ge 0.03 Nb 2 O 8 -TiO 2 -ZnTi 0.97 Ge 0.03 Nb 2 O 8 ceramics with different mass fractions of TiO 2 were initially prepared. The advantages of the multilayer architecture were fully demonstrated, and the microwave dielectric properties were controlled by the components of each dielectric layer. In contrast to the random distribution-type ZnTi 0.97 Ge 0.03 Nb 2 O 8 -TiO 2 , this tri-layer architecture could achieve a nearly 50 % increase in the Q× f value. Meanwhile, based on the parallel distribution mode, a 10 % increase in the dielectric constant could be obtained due to the existence of Zn 2 GeO 4. After sintering at 1120 ℃ for 6 h, ZnTi 0.97 Ge 0.03 Nb 2 O 8 -TiO 2 -ZnTi 0.97 Ge 0.03 Nb 2 O 8 tri-layered ceramics exhibited excellent dielectric properties (ε r = 42.1, Q× f = 51,477 GHz and τ f = +1.9 ppm/℃) with 0.04 wt% TiO 2 , and the cooperative optimization of microwave dielectric properties was achieved. This research provides a direction for the preparation of high-performance microwave dielectric resonators for application in 5 G wireless communication technologies. [ABSTRACT FROM AUTHOR]

In order to better fulfill the requirements high-performance dielectric devices for low insertion loss, compact size, and excellent temperature stability, we propose a strategy to maximize the comprehensive regulation of microwave dielectric properties. Since TiO 2 has a relatively large and positive τ f value, direct addition of TiO 2 has often been utilized to modify the negative τ f value in previous studies. In this paper, TiO 2 and the laminated co-firing technique are applied to monoclinic wolframite structural ceramics. Tri-layer architectural ZnZr 1−x Hf x Nb 2 O 8 -yTiO 2 -ZnZr 1−x Hf x Nb 2 O 8 (0.000 ≤ x ≤ 0.030, 0.01 ≤ y ≤ 0.06) ceramics were synthesized by the laminated co-firing technique. Firstly, Hf4+ ions substituted for Zr4+ ions to significantly enhance the Q × f value of ZnZrNb 2 O 8 system. The modulation effect of Hf4+ on the crystal structure and the influence on the dielectric constant (ε r), Q × f , and τ f values were reasonably demonstrated by combining several characterization approaches with complex chemical bond theory. Compared with pure ZnZrNb 2 O 8, the ZnZr 0.990 Hf 0.010 Nb 2 O 8 ceramic achieved a nearly 65% increase in the Q × f value without excessive deterioration of other dielectric parameters. The laminated co-firing technique was then used to further modulate its ε r and τ f values. Notably, the ZnZr 0.990 Hf 0.010 Nb 2 O 8 -0.05TiO 2 -ZnZr 0.990 Hf 0.010 Nb 2 O 8 tri-layer architectural ceramic achieved prominent comprehensive microwave dielectric characteristics: ε r = 34.34, Q × f = 53,860 GHz, and τ f = + 2.29 ppm/°C, making the tri-layer architecture ceramics attractive for usage in modern microwave communications. • A series of ceramics with the composition ZnZr 1−x Hf x Nb 2 O 8 (x = 0.000, 0.005, 0.010, 0.020, and 0.030) are synthesized using the traditional solid-state reaction approach. • A two-step strategy is proposed for the first time to improve the comprehensive microwave dielectric properties of ZnZrNb 2 O 8 systems. • The effects of Hf4+ substitution on the crystal structure, microstructure, bonding properties, and microwave dielectric characteristics of ceramics with monoclinic wolframite structure were comprehensively investigated. • The ε r value is influenced by the bond ionicity of Nb-O bond. The Q × f value is determined by the lattice energy of Nb-O bond, and the FWHM values of Raman spectra. The τ f value is mostly dependent on the bond energy and bond valence of Nb-O bond. • The microwave dielectric characteristics of the ZnZrNb 2 O 8 system were comprehensively adjusted by the laminated co-firing technique, and the excellent microwave dielectric characteristics were obtained: ε r = 34.34, Q × f = 53,855 GHz, and τ f = + 2.29 ppm/°C. [ABSTRACT FROM AUTHOR]

The ZnTi 1−x Mo x Nb 2 O 8 (0.000 ≤ x ≤ 0.060) microwave dielectric ceramics were prepared through traditional solid-state reaction. Mo4+ substitution for Ti4+ can markedly improve the microwave dielectric characteristics of ZnTiNb 2 O 8 system. In the microstructures investigation, a suitable degree of Mo4+ substitution was shown to be useful for creating uniform grain size and minimizing dielectric loss. Raman spectroscopy and complex chemical bond theory analyses demonstrate that the bond ionicity of Nb O bond is the intrinsic component influencing the ε r value. The lattice energy of Nb O bond, bond valence of Cation-O bond, and the FWHM of Raman spectra were the primary determinants of Q × f value. The τ f value is mostly determined by variations in Nb O bond energy and the bond valence of Cation-O bond. When x = 0.010, ZnTi 0.990 Mo 0.010 Nb 2 O 8 ceramics exhibit excellent microwave dielectric characteristics: ε r = 33.91, Q × f = 64,136 GHz, and τ f = − 50.57 ppm/°C. Furthermore, in order to improve the temperature coefficient of resonant frequency (τ f values close to zero) for the ZnTi 0.990 Mo 0.010 Nb 2 O 8 ceramics, the TiO 2 and laminated co-firing technique were used to adjust the comprehensive microwave dielectric characteristics of the ZnTiNb 2 O 8 system. When the mass fraction of the TiO 2 layer reaches 0.03 wt% after sintering at 1150 °C, the tri-layer structural ZTMN-0.03TO-ZTMN ceramics obtain outstanding microwave dielectric characteristics: ε r = 41.52, Q × f = 50,827 GHz, and τ f = − 2.59 ppm/°C, and these characteristics make them potential for usage in 5G communications. • A two-step strategy is proposed to improve the comprehensive microwave dielectric properties of ZnTiNb 2 O 8 systems. • The effects of Mo4+ substitution on the crystal structure, microstructure, bonding properties, and microwave dielectric characteristics of rutile-like structural ceramics were comprehensively investigated. • Ceramic of ZnTi 0.990 Mo 0.010 Nb 2 O 8 sintered at 1150 °C for 6 h exhibit excellent microwave dielectric characteristics: ε r = 33.91, Q × f = 64,136 GHz, and τ f = − 50.57 ppm/°C. • The bond ionicity of Nb O bond is the intrinsic component influencing the ε r value. The lattice energy of Nb O bond, bond valence of Cation-O bond, and the FWHM of Raman spectra were the primary determinants of Q × f value. The τ f value is mostly controlled by variations in Nb O bond energy and the bond valence of Cation-O bond. • The microwave dielectric characteristics of the ZnTiNb 2 O 8 system were comprehensively adjusted by the laminated co-firing technique, and the excellent microwave dielectric characteristics were obtained: ε r = 41.52, Q × f = 50,827 GHz, and τ f = − 2.59 ppm/°C. [ABSTRACT FROM AUTHOR]

As a candidate of multi-functional material, NdNbO4–xCaTiO3 (x =0, 0.2, 0.4, 0.6, 0.8, 1.0, 3.0wt.%) ceramics with improved microwave dielectric properties were prepared by conventional mixed oxide route. The effects of CaTiO3 addition on the microstructures and microwave dielectric properties of NdNbO4 ceramics were investigated systematically. Microscopic analysis showed that CaTiO3 solubilized into NdNbO4 and substituted for ions. The shift of the main peaks can be demonstrated by the changing of unit cell volumes caused from the substitution of ions. With the addition of CaTiO3 increasing, the microwave dielectric properties of NdNbO4 ceramics were improved. The dielectric constant εr is relative to the ionic polarizabilities and relative densities. The value of quality factors Q × f increases first, and then decreases. The temperature coefficient of the resonant frequency τƒ has a trend of shifting toward zero in the whole range. The variation of Q × f and τƒ could be related to the presence of grain boundaries area, porosity and the second phases. A optical Q × f of 70,000GHz, was achieved for NdNbO4 ceramic doped with 0.6wt.% CaTiO3 sintered at 1275°C for 4h. [ABSTRACT FROM AUTHOR]

Abstract: The effects of H3BO3 addition on the sintering temperature, microstructure and microwave dielectric properties of Li2ZnTi3O8 ceramics were investigated. With H3BO3 addition, the densification of Li2ZnTi3O8 ceramics was improved significantly, the sintering temperature was lowered effectively, and the τf was adjusted to shift toward zero direction. In the case of 1.0wt.% H3BO3 addition, the value of ε r and Q × f reached maximum. With further H3BO3 addition, the dielectric properties were degraded due to the inferior microstructure. With 1.0wt.% H3BO3, the Li2ZnTi3O8 ceramics sintered at 880°C for 4h showed excellent microwave dielectric properties of ε r =25.9, Q × f =50,200GHz, and τf =−6.8ppm/°C. [Copyright &y& Elsevier]

SnO2-doped Li2MgTi3O8 ceramics were successfully synthesized by a solid-state method. The effects of SnO2 addition on the microstructure and dielectric properties of Li2Mg(Ti1−x Sn x )3O8 (x=0.10–0.25)were investigated. Microscopic analysis showed that two phase composition regions were identified in the specimens sintered at 1100°C; [spinel+rutile] at 0.10≤×≤0.15, and [spinel+rutile+ilmenite] at 0.20≤×≤0.25. As SnO2 concentration increased, the temperature coefficient of resonant frequency(τ ƒ) and dielectric constant(ε r ) decreased, which was strongly correlated with the phase composition. However, the quality factor (Q׃) significantly increased with SnO2 content due to the increase of grain size. Especially, the Li2Mg(Ti1−x Sn x )3O8 (x=0.15) ceramics sintered at 1100°C for 4h exhibited good microwave dielectric properties: ε r =26.0, Q׃=74,700GHz and τ ƒ =−5.2ppm/°C. [ABSTRACT FROM AUTHOR]