摘要
近年来，负热膨胀材料因其独特的热膨胀特性和广阔的应用潜力，在材料制备、热缩机理及应用研究各方面得到了长足发展，其性能得到了很大的改善。即便如此，负热膨胀材料的理论及应用研究仍然存在不少亟待解决的问题。介电陶瓷广泛应用于电容、存储、通信等器件中，但介电陶瓷和器件中其它材料热膨胀性能的差异可导致膨胀失配，从而影响器件的使用效果与寿命。针对此问题，本文使用负膨胀材料来调控介电陶瓷的热膨胀和介电性能。研究的主要内容、结果与创新点如下。
1. 可控热膨胀的复合介电陶瓷：SrTiO3/Zr2P2WO12
选用负热膨胀性能较好的Zr2P2WO12 (ZWP)改善介电陶瓷SrTiO3 (STO)的热膨胀性能。采用固相烧结法制备出SrTiO3/Zr2P2WO12可控热膨胀介电陶瓷。研究结果表明，SrTiO3/Zr2P2WO12的热膨胀系数(Coefficient of Thermal Expansion)在9.23×10−6 K−1~2.37×10−6 K−1范围内可调，介电常数在17.15~39.56范围内可调(1 MHz)，耗散因子最小可调至0.002。性能调控后的复合材料在用于电子器件时可以与Si以及SiC等热膨胀系数较低的材料热匹配，解决了热失配的问题。
2. 高频介电陶瓷的制备及性能研究：SrTiO3/ZrMgMo3O12
考虑到Zr2P2WO12烧结温度较高，原料中P2O5的吸水性在制备过程中会增加不确定性，本工作使用制
备方法更简单环保、制作成本更低廉，并且负膨胀性能同样优良的ZrMgMo3O12 (ZMM)替代ZWP与STO进行复合。采用固相烧结法制备了热膨胀性能可控的SrTiO3/ZrMgMo3O12介电陶瓷。实验结果表明，复合材料的热膨胀系数可以从10.13×10−6 K−1调整到4.06×10−6 K−1。在10 MHz时，复合材料介电常数在40.70~21.17范围内可调控，同时，耗散因子介于1.17 ×10−4到79.7×10−4之间。尤其当ZrMgMo3O12体积分数为40%时，该复合陶瓷在10 MHz 时，具有中等介电常数（28.95）以及较低的膨胀系数（6.53×10−6 K−1）和耗散因子(tan =1.17×10−4)。研究表明：SrTiO3/ZrMgMo3O12的介电性能可以满足高频介电陶瓷的应用，热膨胀性能可以与SiC相匹配。
3. ZrMgMo3O12对BaTi4O9介电性能的影响
前面的研究中用ZMM替代ZWP制备复合材料，复合材料的介电性能获得了提升，进一步采用中等介电常数的BaTi4O9(BTO)替代STO与ZMM进行复合。采用固相烧结法制备了BaTi4O9/ZrMgMo3O12复合材料，实验结果表明，BaTi4O9/ZrMgMo3O12复合陶瓷的热膨胀系数随ZrMgMo3O12含量的增加而降低。当ZrMgMo3O12的质量分数为50%时，热膨胀系数 2.79×10−6K−1，可降低到
BaTi 4O 9膨胀系数的约1/3，且谐振频率温度系数降低至4.29×10−6K −1。分析表明，复合陶瓷介电性能的改变主要是由微观结构的变化和复杂的极化机理决定的。本工作通过热膨胀系数来降低谐振频率温度系数：)2
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，不同于以往使用掺杂替代的方法来降低谐振频率温度系数。
4. Sn 元素对ZrMgMo 3O 12介电性能的影响
通过以上对复合材料SrTiO 3/Zr 2P 2WO 12，SrTiO 3/ZrMgMo 3O 12，BaTi 4O 9/ZrMgMo 3O 12性能的研究，发现负膨胀材料Zr 2P 2WO 12和ZrMgMo 3O 12自身的介电性能有待提高。考虑到ZrMgMo 3O 12的应用效果优于Zr 2P 2WO 12，因此接下来研究ZrMgMo 3O 12介电性能的提升。本工作中使用同为+4价的Sn 部分替代ZrMgMo 3O 12中的Zr ，来调节ZrMgMo 3O 12的介电性能。实验结果表明，制备出的Zr 1-x Sn x MgMo 3O 12(x=0.05, 0.10, 0.15, 0.20, 0.25)不仅介电性能较ZrMgMo 3O 12有了大幅提升，热膨胀性能也得到了调控，复合材料的性能和Sn 的替换量以及烧结温度有一定的关系。对于相同的烧结温度来说，随着元素替换量的增加，热膨胀系数负向增大，热膨胀系数在近零膨胀(-0.24×10−6 K −1)和负热膨胀(-8.16×10−6 K −1)范围可调节。ZrMgMo 3O 12的介电常数为5.5，加入Sn 后，Zr 1-x Sn x MgMo 3O 12介电常数在130-155之间可以调控，耗散因子介于4.3×10−4到
5.1×10−4之间。Sn 的掺杂不仅大幅提升了ZrMgMo 3O 12的介电性能，同时还大范围调控了热膨胀系数，因此Zr 1-x Sn x MgMo 3O 12系列材料在高频介电陶瓷领域有很高的应用价值。
关键词：负热膨胀；介电陶瓷；ZrMgMo 3O 12；SrTiO 3；BaTi 4O 9；可控膨胀；膨胀系数；介电性能
Abstract
In recent years, great progress has been made in the development of preparation, thermal shrinkage mechanism, and application rearch of the negative thermal expansion materials due to their unique thermal expansion property and broad application potential. And the performance of negative thermal expansion materials has been greatly improved. Even so, there are still some issues to be solved in both theory and application rearch of negative thermal expansion materials. Dielectric ceramicscan be applied widely, such as capacitor, communications equipment, random access memory. However, thermal mismatch would happenbecau of the difference in thermal expansion performance between dielectric ceramics and other materials, which may affect the valueof application and shortenthe life of the device.Toaddress this issue, negative thermal expansion materials are studied to adjustthe thermal expansion and dielectric properties of dielectric ceramics in this disrtation. The main work, results and innovation points arelisted below.
1. Dielectric ceramic composites with controllable thermal expansion: SrTiO3/Zr2P2WO12年度考核工作总结
Zr2P2WO12 (ZWP) with excellent negative thermal expansion property was ud to adjust thermal expansion property of dielectric ceramic SrTiO3 (STO). SrTiO3/Zr2P2WO12 composites were prepared by using the solid-state method. Results showed that the thermal expansion coefficients could be adjusted in the range of (9.23–2.37) ×10−6K−1, Meanwhile, the dielectric constants changed between 17.15 and 39.56 (1 MHz),and the dissipation factorcan be adjusted to a minimum of 0.002. After performance regulation, the thermal expansion property of the composites can match with Si and SiC when the composites are ud in electron devices.
霜雨2. The preparation and properties of high-frequency dielectric ceramics: SrTiO3/ZrMgMo3O12
Given the high sintering temperature (1673 K) of Zr2P2WO12, and the uncertainty caud by hydroscopicity of the raw material P2O5, ZrMgMo3O12 (ZMM), which is simpler and cheaper to produce and has excellent negative expansion performance,was considered to replace ZWP and combined with STO in this work.Dielectric ceramic compositesSrTiO3/ZrMgMo3O12with controllable thermal expansionhad been fabricated by solid-state method. The experimental results indicated that CTEs of the composites could be adjusted from 10.13×10−6 to
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4.06×10−6 K −1. At 10 MHz, dielectric constants of composites were in the range of 40.70–21.17, w
hile dissipation factors are between 1.17 10−4and 79.7 10−4. The composite wherein the volume fraction of ZrMgMo 3O 12 was 40 % showed the following excellent properties: low CTE (6.53×10−6 K −1), moderatedielectric constants (28.95) and low dissipation factor (tanδ, 1.17×10−4) at 10 MHz. Therefore, this composite could not only be ud as a high-frequency dielectric ceramic, but also match with the thermal expansion of SiC.
3. The influence of ZrMgMo 3O 12 on the dielectric properties of BaTi 4O 9
In the previous rearch, ZMM replaced ZWP to prepare composite materials, and the dielectric properties were improved. Furthermore, BaTi 4O 9 (BTO) with medium dielectric constant was ud to replace STO to recombine with ZMM.BaTi 4O 9/ZrMgMo 3O 12 composites were prepared by a solid state method. The results showed that the CTE of BaTi 4O 9/ZrMgMo 3O 12 composites decread as the content of ZrMgMo 3O 12increasing. And when the content of ZrMgMo 3O 12 reached 50%, theCTE would be 2.79×10−6 K −1, which was about 3/1of that of BaTi 4O 9. Besides, thetemperature coefficient of resonance frequency (τf ) was 4.29×10−6 K −1.The changes in dielectric properties of composite samples can be mainly attributed to the changes of microstructure and complex polarization mechanism. And temperature coefficient of resonance frequency (τf ) was regulated by the CTE owing to )2
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4. Effect of Sn on the dielectric properties of ZrMgMo 3O 12
From the above rearch on the properties of composites SrTiO 3/Zr 2P 2WO 12, SrTiO 3/ZrMgMo 3O 12 and BaTi 4O 9/ZrMgMo 3O 12, it was found that the dielectric properties of NTE materials Zr 2P 2WO 12 and ZrMgMo 3O 12 need to be improved. Given that the application value of ZrMgMo 3O 12 is better than Zr 2P 2WO 12, this work focud on improvement of the dielectric properties of ZrMgMo 3O 12: Sn, having the samevalence (+4) as Zr in ZrMgMo 3O 12, was ud to partially replace Zr to adjust its dielectric properties. The results showed that not only the dielectric properties of Zr 1-x Sn x MgMo 3O 12 (x=0.05, 0.10, 0.15, 0.20, 0.25) sampleswere improved significantly, but also thermal expansion performance was regulated compared to ZrMgMo 3O 12. Both the substitution amount of Sn and sintering temperature had a certain effect on the properties of Zr 1-x Sn x MgMo 3O 12. For the same sintering
日光照temperature, the CTEs became larger toward negative as the amount of Sn incread.The CTEs can be adjustedbetween near zero thermal expansion (ZTE) (-0.24×10−6K−1) and NTE (-8.16×10−6K−1). While the dielectric constant of ZrMgMo3O12 is about 5.5, the ones of Zr1-x Sn x
MgMo3O12 can be adjusted in therange of 130-155.The dissipation factors of Zr1-x Sn x MgMo3O12were adjustable between 4.3×10-4and 5.1×10-4. Sn has significantly improved the dielectric properties of ZrMgMo3O12; meanwhile,the CTEs were adjusted in a large range. As a result, Zr1-x Sn x MgMo3O12 materials have high value in the field of high-frequency dielectric ceramics.
生疏的拼音
Key words: Negative thermal expansion; ZrMgMo3O12；SrTiO3；BaTi4O9；Controllable thermal expansion; Coefficient of thermal expansion; Dielectric property
