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Bismuth‐layered ferroelectric materials with Aurivillius structure are the potential materials for high‐temperature ferroelectric materials because of their high Curie temperature and excellent ferroelectric fatigue resistance. Herein, the Aurivillius phase relaxation ferroelectrics as Ban−3Bi4TinO3n+3 (n = 4–7) ceramics are studied. The layered structures are controlled by adjusting the number of BO6 octahedrons and (Bi2O2)2+ layers. The dielectric temperature stability and voltage resistance of bismuth barium titanate ceramics are improved. The influence of composition and microstructure on their electrical properties is explored. The relationship between dielectric properties and storage properties of bismuth barium titanate ceramics and the number of layers is obtained. Ba2Bi4Ti5O18 ceramics show the best performance with an energy storage density of up to 1.16 J cm−3 and a high efficiency of ≈87.2% (under 250 kV cm−1). This work provides key materials and technologies for the next generation of energy storage capacitors that can be applied in high‐temperature environments as well as a new reference for the development of dielectric materials and the functional optimization of other Aurivillius phase ceramic materials. [ABSTRACT FROM AUTHOR]

Abstract MoO 3 ceramics can not be well densified via conventional solid state method and a low relative density (ρ) was obtained (˜64.5% at 680 °C) with a permittivity (ε r) ˜ 7.58, a quality factor (Qf) ˜ 35,000 GHz and a temperature coefficient of resonant frequency (TCF) ˜ − 39 ppm/°C. However, cold sintering at 150 °C using 4 wt. % H 2 O at 150 MPa enhanced densification and give a relative ρ ˜76.8% and ε r ˜ 8.31 but with a Qf of only ˜ 900 GHz. The addition of (NH 4) 6 Mo 7 O 24 ·4H 2 O further improved densification to give a relative ρ ˜ 83.7% after annealing at 700 °C, resulting in a ε r ˜ 9.91 with a Qf ˜ 11,800 GHz. We conclude therefore that oxides that are difficult to be sintered via a conventional solid state route may benefit from cold sintering but despite the higher density, lower Qf cannot be avoided due to the impurities and grain boundary phases that are introduced. [ABSTRACT FROM AUTHOR]

Abstract A scheelite structured [Ca 0.25 (Nd 1-x Bi x) 0.5 ]MoO 4 (0.2 ≤ x ≤ 0.8) ceramics were prepared via solid state reaction method. All the ceramics can be well densified below 780 °C. As x value increased from 0.2 to 0.8, microwave dielectric permittivity increased from 14.0 to 27.8, Qf (Q = quality factor = 1/dielectric loss; f = resonant frequency) value decreased from 42,000 GHz to 19,000 GHz, and TCF shifted from −50 ppm/oC to +18 ppm/oC. The best microwave dielectric properties with permittivity between 23.54 and 23.56, Qf value between 24,000 GHz–21,000 GHz and TCF value ∼ −8 ppm/oC in wide temperature range 25 °C–130 °C were obtained in x = 0.6 ceramic. This work showed that Bi played an important role to modify the TCF from negative to positive value in scheelite materials and this result further accelerate the application of scheelite materials in low temperature co-fired ceramics (LTCC) technology. Highlights • Defect type scheelite [Ca 0.25 (Nd 1-x Bi x) 0.5 ]MoO 4 ceramics were formed. • Near zero TCF was obtained with a ɛ r 23.54 and Qf value 24,000 GHz. • Low sintering temperature ∼ 780° were achieved. [ABSTRACT FROM AUTHOR]

Abstract: K0.5(Nd1−xBix)0.5MoO4 (0.2 ≤ x ≤ 0.7) ceramics were prepared via the solid‐state reaction method. All ceramics densified below 720°C with a uniform microstructure. As x increased from 0.2 to 0.7, relative permittivity (ɛr) increased from 13.6 to 26.2 commensurate with an increase in temperature coefficient of resonant frequency (TCF) from – 31 ppm/°C to + 60 ppm/°C and a decrease in Qf value (Q = quality factor; f = resonant frequency) from 23 400 to 8620 GHz. Optimum TCF was obtained for x = 0.3 (−15 ppm/°C) and 0.4 (+4 ppm/°C) sintered at 660 and 620°C with ɛr ~15.4, Qf ~19 650 GHz, and ɛr ~17.3, Qf ~13 050 GHz, respectively. Ceramics in this novel solid solution are a candidate for ultra low temperature co‐fired ceramic (ULTCC) technology. [ABSTRACT FROM AUTHOR]

(Bi 1−x Ln x ) 2 MoO 6 (Ln=Nd and La) ceramics were prepared by conventional solid state reaction method. Solid solutions crystallizing in a monoclinic structure with a space group P 21/ c were obtained in the (Bi 1−x La x ) 2 MoO 6 (x≤0.3) ceramics. For the (Bi 1−x Nd x ) 2 MoO 6 ceramics, tetragonal Nd 2 MoO 6 phase with a space group I4 1 /acd was detected when x value reached 0.2 besides the Bi 2 MoO 6 solid solution. Temperature stability and quality factor Qf value at microwave frequencies were improved by appropriate substitution for Bi 3+ by Nd 3+ and/or La 3+ in Bi 2 MoO 6 system. When x=0.2, for both (Bi 1−x Nd x ) 2 MoO 6 and (Bi 1−x La x ) 2 MoO 6 ceramics, Qf values reached maximum about 30,200 GHz and 32,900 GHz, respectively. TCF value shifted towards zero with substitution of Bi 3+ by Nd 3+ and/or La 3+ . When x=0.3, TCF values of (Bi 1−x Nd x ) 2 MoO 6 and (Bi 1−x La x ) 2 MoO 6 ceramics were −70 and −85 ppm/°C, respectively. Relation between crystal structure, microstructure and microwave dielectric properties were discussed. [ABSTRACT FROM AUTHOR]

Low firing microwave dielectric ceramics Bi 3 (Nb 1− x V x )O 7 ( x =0.0, 0.1, 0.2, 0.3, and 0.5) were prepared by the solid state reaction method. Sintering behavior, crystalline structure, microstructure, and microwave dielectric properties were studied. Temperature stable low-firing microwave dielectric ceramics with high permittivity were obtained in the Bi 3 (Nb 1− x V x )O 7 system when x =0.1 and 0.2. The Bi 3 (Nb 0.9 V 0.1 )O 7 and Bi 3 (Nb 0.8 V 0.2 )O 7 ceramics sintered at 870 °C for 2 h were found to possess high permittivity of 80 and 76, Qf (quality factor) values of 615 and 460 GHz, and TCF (temperature coefficient of frequency) values of −22 and+3.3 ppm/°C, respectively. [ABSTRACT FROM AUTHOR]

Ag2 MoO4 ceramic was prepared by using the solid-state reaction method, which could be sintered at 450°C for 2 h, having a relative permittivity of 8.08, a Qf value of 17 000 GHz, and a temperature coefficient of resonance frequency about −133 ppm/°C. Ag2 MoO4 ceramic was chemically compatible with silver but reacted seriously with aluminum to form ( Ag0.5 Al0.5) MoO4 during the sintering. The fitting of infrared spectra and the Shannon's additive rule were employed to study intrinsic dielectric behaviors of the ceramics at microwave region. Ionic displacive polarization and the electronic polarization contributed almost equally to the dielectric permittivity of the ceramic at microwave region. The Ag2 MoO4 ceramics could be a good candidate for ultra-low temperature co-fired microwave devices. [ABSTRACT FROM AUTHOR]

In the present work, ( Bi1− x Fe x) VO4 ( x ≤ 0.40) ceramics were prepared using the solid-state reaction method. All the ceramics could be well densified at sintering temperatures below 800°C. X-ray diffraction ( XRD) results showed that monoclinic solid solution was formed within x ≤ 0.08. When x ≥ 0.10, both monoclinic scheelite and FeVO4 phases were detected. The ( Bi0.92 Fe0.08) VO4 sample sintered at 720°C for 2 h had a permittivity of 57.5 and a Qf value of 15 000 GHz. The IR reflectivity was fitted to study the intrinsic dielectric properties, showing that the majority of the dielectric contribution for this system at microwave region was attributed to the absorptions of structural phonon oscillation in infrared region. [ABSTRACT FROM AUTHOR]

Abstract: A Bi(In1/3Mo2/3)O4 ceramic was prepared via the solid state reaction method. The pure monoclinic phase was formed at around 650°C. Ceramic samples with relative densities above 97% were obtained when sintering temperature was around 840°C. The best microwave dielectric properties were achieved in the Bi(In1/3Mo2/3)O4 ceramic sintered at 840°C for 2h with permittivity ∼25.2, Qf of 40,000GHz and temperature coefficient of resonance frequency ∼−65ppm/°C at 8.2GHz. The temperature dependence of microwave dielectric properties was also studied in a wide temperature range from −250°C to +120°C. The Qf value increased with the decrease of temperature and reached a maximum of 150,000GHz at −250°C. [Copyright &y& Elsevier]

Abstract: The Bi3SbO7 ceramic was prepared by the solid state reaction method and its phase evolution at different temperatures was studied. Low temperature phase α-Bi3SbO7 was formed at about 890°C and it started to transform to high temperature phase β-Bi3SbO7 at about 960°C. Microwave dielectric constants of α-Bi3SbO7 ceramic and β-Bi3SbO7 ceramic were 43.2 and 37.6, Qf value were 2080 and 5080GHz, respectively. TCF of α-Bi3SbO7 ceramic was near zero and TCF of β-Bi3SbO7 ceramic was about −120ppm/°C. The Bi3SbO7 ceramic is a promising candidate for low temperature co-fired ceramic (LTCC) technology due to its large dielectric constant, low dielectric loss at microwave region, low sintering temperature and simple composition. [Copyright &y& Elsevier]

Abstract: The phase structure, microwave dielectric properties, and their stability with different annealing conditions have been investigated in (Li1/4Nb3/4) substituted Zr x Sn y Ti z O4 system. The sintering temperature of Zr x Sn y Ti z O4 ceramic was lowered from 1500 to 1140°C by (Li1/4Nb3/4) substitution. Both X-ray diffraction (XRD) analysis and electron diffraction (ED) analysis revealed that the (Li1/4Nb3/4) substituted Zr x Sn y Ti z O4 ceramic crystallized as the high-temperature disordered ZrTiO4 phase. As the content of Sn increased from 0.10 to 0.30, the permittivity of the (Zr1−x Sn x )(Li1/4Nb3/4)0.4Ti0.6O4 ceramic decreased gradually from 35.5 to 31.5, the Q f value increased from 37,800 to 58,300GHz, and TCF value shifted slightly from −4.5 to −33.0ppm°C−1. Both the phase structure and microwave dielectric properties of (Zr1−x Sn x )(Li1/4Nb3/4)0.4Ti0.6O4 ceramics were stable with annealing conditions. [ABSTRACT FROM AUTHOR]

The phase evolution, Raman spectroscopy and microwave dielectric properties of (LiNb) doped ZrO-TiO system were investigated. The effects of the Zr/Ti ratio and the (LiNb) substitution were addressed. X-ray diffraction and electron diffraction analysis showed that the crystalline phases of the (LiNb) doped ZrO-TiO ceramics depended greatly on the Zr/Ti ratio. The sample with Zr/Ti ratio of 7/9 crystallized as ZrTiO phase structure, a commensurate structure with a tripled a-axis superstructure and a ZZ sequence. Secondary phase of monoclinic ZrO phase appeared when the Zr/Ti ratio was as high as 9/7. Raman analysis showed that the Raman peaks located at 651 and 624 cm were assigned to the vibration modes of Zr-O octahedron and Ti-O octahedron, respectively. The dielectric constant and quality factor ( Qf value) of the (LiNb) doped ZrO-TiO ceramics decreased slightly as the Zr/Ti ratio changed from 6/10 to 9/7. The temperature coefficient of resonate frequency ( TCF value) was sensitive to the Zr/Ti ratio and it showed a negative value when the Zr/Ti ratio was close to 5:7. Meanwhile, the TCF value of ZrO-TiO ceramics could also be tailored by the (LiNb) substitution. [ABSTRACT FROM AUTHOR]

Abstract: A new temperature stable microwave dielectric with low-firing temperature in xBi2MoO6–(1− x)TiO2 system was prepared by conventional solid state reaction method. The crystalline phases, sintering behavior, microwave dielectric properties of xBi2MoO6–(1− x)TiO2 ceramics were studied. All the xBi2MoO6–(1− x)TiO2 ceramics could be well sintered at 850°C for 3h. X-ray diffraction analysis showed that tetragonal rutile phase and monoclinic Bi2MoO6 phase coexisted in the ceramic. The permittivity ɛ r changed from 77.5 to 33.5 and the temperature coefficient of resonant frequency τ f value shifted from +348.1 to −37.8ppm/°C as the x value increased from 0.06 to 0.65. The temperature stable microwave dielectric ceramic was obtained when x =0.57 in the xBi2MoO6–(1− x)TiO2 system, and it showed excellent dielectric properties of ɛ r =36.7, Qf=16,800GHz and τ f =0ppm/°C. [Copyright &y& Elsevier]

Abstract: Both Li3TaO4 and Li3SbO4 ceramics were prepared via the solid state reaction method. With 1wt.% B2O3 addition, the sintering temperatures of both Li3TaO4 and Li3SbO4 ceramics can be lowered to near 930°C. The chemical compatibility of silver electrode and the low-firing ceramics has been considered, and the results showed that both the Li3TaO4 and Li3SbO4 ceramics are chemical compatible with Ag. Good microwave dielectric properties were obtained with permittivities of 14.1 and 10.3, quality factor Q f values of 29,900 (at 12.4GHz) and 14,600GHz (at 13.5GHz), and temperature coefficient of resonant frequency values of −48 and −28ppm/°C for Li3TaO4 and Li3SbO4 ceramics with 1wt.% B2O3 addition, respectively. [Copyright &y& Elsevier]

Abstract: A low firing microwave dielectric ceramic BaLa2(MoO4)4 with monoclinic structure was prepared via a solid state reaction method. The BaMoO4 and La2(MoO4)3 phases were first formed at 600°C and then the monoclinic BaLa2(MoO4)4 phase was formed gradually above 700°C. Dense and homogeneous microstructure can be obtained in ceramic sample sintered at 800–860°C for 2h with grain size lying between 3–7μm. Optimal microwave dielectric properties can be obtained in ceramic sintered at 860°C for 2h with a permittivity of ~10.3, a Qf value of ~29,800GHz and a temperature coefficient of resonant frequency of ~−76ppm/°C at about 9.9GHz. [Copyright &y& Elsevier]

Abstract: Ln2Mo3O12 (Ln=La, Nd) ceramics with a defect scheelite related structure were prepared via a solid state reaction method. The La2Mo3O12 ceramics sintered at 930°C for 2h exhibited a low dielectric permittivity of 10.1, a high quality factor (Qf value) of 60,000GHz and a temperature coefficient of −80ppm/°C at 12.7GHz. The Nd2Mo3O12 ceramics sintered at 945°C for 2h possessed a dielectric permittivity of 8.2, a Qf value of 80,000GHz, and a temperature coefficient of −60ppm/°C at 15.8GHz. This group of ceramics could be good candidates for microwave substrate applications. [ABSTRACT FROM AUTHOR]

Abstract: A series of (ABi)1/2MoO4 (A=Li, Na, K, Rb, Ag) compositions were studied in regard to the sintering behavior, phase composition, microwave dielectric properties and chemical compatibility with silver and/or aluminum for electrodes. All the (ABi)1/2MoO4 (A=Li, Na, K, Rb, Ag) ceramics could be sintered below 700°C with relative densities above 93%. Whereas the (KBi)1/2MoO4 ceramic can be sintered to a high density at around 630°C/2hrs with a relative permittivity ∼37, a Qf value of 4000GHz and a temperature coefficient of resonant frequency (TCF)∼ +117ppm/°C. Furthermore, from the XRD analysis of co-fired ceramics, the (KBi)1/2MoO4 ceramic reacts with silver but not with aluminum at its densification temperature. The (ABi)1/2MoO4 (A=Li, Na, K, Rb, Ag) type ceramics can all be considered into the new field of ultra-low temperature co-firing dielectrics for multilayer applications. [Copyright &y& Elsevier]

Abstract: Effects of 1.0wt.% V2O5–CuO mixture addition on the sintering behavior, phase composition and microwave dielectric properties of BiSbO4 ceramics have been investigated. BiSbO4 ceramics can be well densified below temperature about 930°C with 1.0wt.% V2O5–CuO mixtures addition with different ratios of CuO to V2O5. The formation of BiVO4 phase and substitution of Cu2+ can explain the decrease of sintering temperature. Dense BiSbO4 ceramics sintered at 930°C for 2h exhibited good microwave dielectric properties with permittivity between 19 and 20.5, Qf values between 19,000 and 40,000GHz and temperature coefficient of resonant frequency shifting between −71.5ppm°C−1 and −77.8ppm°C−1. BiSbO4 ceramics could be a candidate for microwave application and low temperature co-fired ceramics technology. [Copyright &y& Elsevier]

Abstract: In the present work, the 0.3Li2TiO3–0.7Li(Zn0.5Ti1.5)O4 ceramic was prepared via the conventional solid state reaction route, and the phase composition, microstructure, and sintering behavior were investigated. The ceramic sample sintered at 1100°C for 2h demonstrated high microwave dielectric performance with a relative permittivity of 23.5, a high quality factor (Qf) ~88,360GHz (at 7.4GHz), and near zero temperature coefficient of resonant frequency about −0.8ppm/°C. These results indicate that the 0.3Li2TiO3–0.7Li(Zn0.5Ti1.5)O4 ceramic might be a good candidate for dielectric resonators, filters and other microwave electronic device applications. [Copyright &y& Elsevier]