This invention relates to a multiphase ceramic material with a giant dielectric constant and its preparation method.
Researches on the miniaturization of high-energy storage devices, supercapacitors and other equipment have shown that as an indispensable part of these devices and equipment, the dielectric material needs to simultaneously possess a giant dielectric constant, a low dielectric loss, and good frequency- and temperature-stability, and the high breakdown strength. The capacity of the energy storage device/equipment is proportional to the square of the working voltage of the dielectric material, suggesting that it is necessary to study the breakdown strength of dielectric ceramic materials.
Numerous studies have shown that ferroelectric materials, such as BaTiO3, have a high dielectric constant. However, their dielectric constant is highly dependent on temperature. For other non-ferroelectric materials, such as CaCuTi3O12 (CCTO), doped NiO and La2xSrxNiO4 (x=⅓, ⅛), etc., although their dielectric constant can reach 105 or more within a wide temperature range, their dielectric loss is very high (>0.1).
Therefore, there is a need to prepare a dielectric ceramic material with a high dielectric constant, a low dielectric loss, good temperature- and frequency-stability, and high breakdown strength.
The objective of the present invention is to provide a multiphase ceramic material with a giant dielectric constant to overcome the deficiencies of the prior art.
The technical solution of the present invention is a multiphase ceramic material with a giant dielectric constant, wherein the multiphase ceramic material has a general formula of AxBnxTi1−(n+1)xO2, wherein A is at least one selected from the group consisting of Nb, Ta, V, Mo, and Sb, B is at least one selected from the group consisting of In, Ga, Al, Co, Cr, Sc, Fe (III), and a trivalent rare-earth cation; n is a molar ratio of B to A, 1<n≤5, 0<x≤0.1.
The multiphase ceramic material of the present application possesses outstanding dielectric properties including a giant dielectric constant, a low dielectric loss, and good frequency- and temperature-stability. In particular, it exhibits a high insulation resistivity and a high breakdown voltage. The ceramic material has an insulation resistivity of higher than 1011Ψ·cm; it can be applied in high-energy storage devices and supercapacitors.
Preferably, a primary phase of the ceramic material is A5+ and B3+ co-doped rutile TiO2, a secondary phase of the ceramic material is B2TiO5; the secondary phase is evenly dispersed in the primary phase. The primary phase provides the multiphase ceramic material with the giant dielectric property, while the secondary phase exhibits excellent electrical insulation properties. The secondary phase is discontinuously and uniformly distributed around the grain boundary of the primary phase. Therefore, it can effectively block the transfer of weakly bounded charges, which contributes to increasing the working voltage and breakdown voltage of the material. Meanwhile, the existence of the secondary phase does not cause the deterioration of the giant dielectric property of the material.
More preferably, the secondary phase is B2TiO5 with an orthogonal structure. During a one-step synthesis process, the secondary phase has a lower synthesis temperature comparing to that of the primary phase, helping to separate two phases.
Preferably, the multiphase ceramic material has a resistivity of higher than 1011Ω·cm.
Preferably, the multiphase ceramic material has a dielectric constant of higher than 10,000 at a frequency of 20 Hz to 2×106 Hz; the multiphase ceramic material has a dielectric loss of less than 0.05, when the frequency is lower than 2×105 Hz.
Preferably, the multiphase ceramic material has a dielectric constant of higher than 10,000 from −160° C. to 170° C.; the multiphase ceramic material has a dielectric loss of less than 0.05 from −50° C. to 150° C.
The present invention also provides a method of preparing the multiphase ceramic material with a giant dielectric constant, the method comprises steps of:
Preferably, in step 1, the titanium source is TiO2, the A source is A2O5, the B source is at least one selected from the group consisting of B2O3, B2(C2O4)3, B2(C2O4)3 hydrate, B(NO3)3, B(NO3)3 hydrate, B2(SO4)3, B2(SO4)3 hydrate, B2(CO3)3, B2(CO3)3 hydrate, B(C2H3O2)3, B(C2H3O2)3 hydrate.
The non-oxide B source can reduce the synthesis temperature of the secondary phase and reduce its mobility around the grain boundary, helping to form a discontinuously and uniformly distributed B phase.
Preferably, the ball-milling in step (2) comprises using ethanol or acetone as a dispersant, and using yttrium-stabilized zirconia balls as a ball-milling medium; ball-milling is performed for more than 12 hours; in steps (4) and (5), an atmosphere for the sintering and the annealing is air.
Preferably, the polishing of the surface in step (5) comprises rough polishing the surface by a 240-grit sandpaper, followed by finely polishing the surface by a 1200-grit sandpaper
Compared with the prior art, the advantages of the present invention are discussed below.
In the present invention, rutile titanium dioxide is chemically modified by co-doping A5+ and B3+ metal ions to obtain a multiphase material, in which the primary phase is A5+ and B3+ co-doped rutile TiO2 and the secondary phase (B2TiO5) is evenly dispersed in the primary phase. The multiphase ceramic material of the present application has outstanding properties including a giant dielectric constant, a low dielectric loss, and good frequency- and temperature-stability. In particular, it has a high insulation resistivity and a high breakdown voltage. The ceramic material can be used in high-energy storage devices and supercapacitors. Its detailed advantages are:
The objectives, technical solutions, and beneficial effects of the present invention will be described below with reference to the accompanying drawings and embodiments.
Embodiment 1 is one of the embodiments in the present invention. The multiphase ceramic material of this embodiment has a general formula of AxBnxTi1−(n+1)xO2, where A is Nb, B is In, x=0.0125, and n=2.
The detailed method to synthesize this embodiment comprised the following steps:
Embodiment 2 is one of the embodiments in the present invention. The multiphase ceramic material of this embodiment has a general formula of AxBnxTi1−(n+1)xO2, wherein A is Nb, B is In, x=0.075, and n=2.
The detailed method to synthesize this embodiment comprised the following steps:
Embodiment 3 is one of the embodiments in the present invention. The multiphase ceramic material of this embodiment has a general formula of AxBnxT1−(n+1)xO2, wherein A is Nb, B is In, x=0.0125, and n=3.
The detailed method to synthesize this embodiment comprised the following steps:
Embodiment 4 is one of the embodiments in the present invention. The multiphase ceramic material of this embodiment has a general formula of AxBnxTi1−(n+1)xO2, wherein A is Nb, B is In, x=0.0125, and n=4.
The detailed method to synthesize this embodiment comprised the following steps:
Table 2 summarizes the resistivity, the dielectric constant and the dielectric loss of the ceramic materials prepared in embodiments 1, 3, and 4 and a reference material:
Compared with the reference material (1.25 at % Nb5+1.25 at % In3+), the materials of embodiments 1, 3 and 4 have higher resistivity, as well as a high dielectric constant (>10,000) and low dielectric loss (<0.05). This suggests that because the secondary phase is discontinuously and uniformly distributed at the grain boundary of the primary phase, it effectively blocks the movement of weakly bounded charges, contributing to high working voltage and breakdown voltage of the material. Meanwhile, the existence of the secondary phase does not cause the deterioration of the giant dielectric property of the material.
At last, it should be noted that the aforementioned embodiments are only used to illustrate the technical solutions of the present invention that does not limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solution of the present invention can be modified without deviating from the essence and scope of the technical solution of the present invention.
Number | Date | Country | Kind |
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202010205096.0 | Mar 2020 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2020/081953 | 3/29/2020 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2021/184414 | 9/23/2021 | WO | A |
Number | Name | Date | Kind |
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9809499 | Hirahara | Nov 2017 | B2 |
20100175735 | Uchida | Jul 2010 | A1 |
20140293506 | Hu | Oct 2014 | A1 |
Number | Date | Country |
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103958414 | Jul 2014 | CN |
110577401 | Dec 2019 | CN |
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Wanbiao Hu et al., Colossal Dielectric Permittivity in (Nb+Al) Codoped Rutile TiO2 Ceramics: Compositional Gradient and Local Structure, Chemistry of Materials, Jun. 25, 2015, ISSN:0897-4756, pp. 4934-4942, vol. 27, No. 14. |
Baochun Guo, Study on the regulation of giant dielectric properties and polarization relaxation of doped TiO2 ceramics, Chinese Doctoral Dissertations Full-text Database, Nov. 1, 2018, pp. 30-50. |
Number | Date | Country | |
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20220127197 A1 | Apr 2022 | US |