制备方法对磷酸盐微晶玻璃结构和性能的影响
1.
2.
3.
Effect of Preparing Methods on Structure and Properties of Phosphate Glass-ceramics
1.
2.
3.
通讯作者: 周毅,副教授,zhouyi@tyust.edu.cn,研究方向为无机非金属材料
收稿日期: 2023-01-05 修回日期: 2023-02-08
基金资助: |
|
Corresponding authors: ZHOU Yi, Tel:
Received: 2023-01-05 Revised: 2023-02-08
Fund supported: |
|
作者简介 About authors
周毅,男,1984年生,博士
分别用熔融法和烧结法制备P2O5-Nb2O5-BaO-Na2O-CeO2体系磷酸盐微晶玻璃,用XRD谱和SEM观察表征其结构并测定其体积密度、显微硬度、介电性能、极化性能和储能特性,研究了制备工艺对其结构和性能的影响。结果表明,用熔融法可制备出结构更致密的微晶玻璃,使其体积密度和显微硬度提高和降低其介电损耗。当CeO2添加量提高到1%(摩尔分数)时,用两种工艺都可实现微晶玻璃的结构致密化,并促进其结晶。结晶程度的提高可改善微晶玻璃的介电常数和极化性能。用熔融法制备的CeO2添加量为1%(摩尔分数)的微晶玻璃样品其能量释放密度为13.5 mJ/cm3、储能效率为50.1%。
关键词:
Gass-ceramics can be well used for making energy storage capacitors because of their unique structure of crystalline particles uniformly distributed in the glass matrix. Compared with conventional silicon glass-based glass-ceramics, phosphate glass-ceramics have significant advantage of less energy consumption. In this study, glass-ceramics of P2O5-Nb2O5-BaO-Na2O-CeO2 were prepared by melting and sintering respectively. The structure of the prepared phosphate glass-ceramics was characterized through XRD and SEM. The effect of preparation method on the structure and properties of the phosphate glass-ceramics were systematically studied in terms of the bulk density, microhardness, dielectric properties, polarization performance and energy storage etc. The results showed that the more compact glass-ceramics could be obtained by the melting method, which could improve the bulk density and micro-hardness of the glass-ceramics, the corresponding dielectric loss was reduced. In addition, when the addition of CeO2 was increased to 1% (mole fraction), the phosphate glass-ceramics obtained by the two methods were also achieved good densification. The addition of CeO2 played a role in promoting crystallization, which enhanced the dielectric constant and polarization performance. The released energy density of 13.5 mJ/cm3 and energy storage efficiency of 50.1% were obtained for the glass-ceramic with addition of 1% CeO2 (mole fraction) prepared by melting method.
Keywords:
本文引用格式
周毅, 涂强, 米忠华.
ZHOU Yi, TU Qiang, MI Zhonghua.
制备微晶玻璃的方法,有熔融快冷法(简称熔融法),烧结法和溶胶凝胶法。溶胶凝胶法使用的原料是金属有机物,原料成本较高、工艺复杂流程较长且产率低;熔融法和烧结法没有溶胶凝胶法的这些不足[12~14]。用熔融法制备微晶玻璃材料,先将原料混合物熔融并均匀化,然后将其浇注到金属模具或金属轧辊中快冷生成玻璃原片,再将其去应力退火,在特定温度下控制析晶的生成使晶粒均匀分布在玻璃基体中。烧结法是将配制的原料熔融并均匀化,然后将熔液倒入水中形成玻璃熔块,再将其研磨或球磨制成玻璃粉。用类似制备陶瓷的工艺将玻璃粉配以粘结剂在金属模具中干压成型,然后在特定温度烧结而制备出微晶玻璃。本文用熔融法和烧结法制备磷酸盐微晶玻璃,并研究其对结构、力学与介电性能的影响。
1 实验方法
1.1 样品的制备
实验用原料有分析纯的NH4H2PO4(>99.9%)、Nb2O5(>99.9%)、BaCO3(>99.9%)、Na2CO3(>99.9%)和CeO2(>99.9%)。按照35P2O5-35Nb2O5-22BaO-6Na2O-xCeO2(x=0、0.5、1、1.5)的摩尔比配料。将各配比原料称量后装入玛瑙研磨罐中球磨混合12 h,球磨介质为无水乙醇。然后将其在80℃干燥4 h。将球磨并干燥后的各配比原料平均分成两份并分别装入一个高纯刚玉坩埚中,以5℃/min的速度升温至1150℃并保温1 h。将其中一只坩埚内的熔液浇注到450℃的不锈钢模具中得到玻璃原片,然后将其快速移回450℃预热炉中退火4 h以消除应力。最后以5℃/min的速度将去除应力的玻璃原片升温至900℃并保温2 h进行晶化。晶化后冷却即得到用熔融法制备的微晶玻璃样品。
将另一只坩埚内的熔液迅速倒入盛有多半桶去离子水的金属桶里,得到若干玻璃熔块。待熔块的温度降至室温后将其从去离子水中捞出并在100℃干燥4 h。然后将干燥的熔块打碎并球磨4 h后过200目标准筛。将筛下的玻璃粉用浓度为3%(质量分数)的PVA溶液造粒,然后模压制成若干厚度约为1 mm、直径8 mm的薄片。将薄片以5℃/min的速度升温至900℃并保温2 h,冷却后即得到用烧结法制备的微晶玻璃样品。
用精密磨抛机(P25FR-HA, Taiwan, China)将用两种方法所制备的微晶玻璃样品表面研磨和抛光,使其厚度约为0.4~0.5 mm。用丝网印刷技术在微晶玻璃介质片两表面制备直径为6 mm的中温银浆电极并将其在600℃烘烤0.5 h。
1.2 性能表征
用XRD衍射仪(XRD-7000, Shimadzu, Japan)表征磷酸盐微晶玻璃的物相结构,光源为Cu Kα,扫描速率为2 (°)/min,扫描范围20°~70°。用扫描电子显微镜(SEM; S-4800, Hitachi, Japan)表征微观结构,样品表面做喷金处理。用Archimedes法和去离子水测试样品的体积密度
其中m为样品在空气中质量,mw为样品在去离子水中的质量,ρw为去离子水在常温常压时的密度。用数字显微硬度仪测试样品的显微维氏硬度(HV)和努氏硬度(HK),基于压痕法测试硬度,分别为
其中F为载荷,
其中C为电容值,d为介质片的厚度,
其中E为应用场强,
2 结果和讨论
图1给出了分别用熔融法和烧结法制备的磷酸盐微晶玻璃的XRD谱。物相检测结果表明,用两种方法制备的微晶玻璃样品都含有结晶相BaNb2P2O11(PDF#40-0107)和Nb(PO4)O(PDF#76-2125)。结晶相的产生与制备方法没有直接关系,只与原料有关。特征峰强度的变化表明,随着CeO2的添加量从0提高到1%(摩尔分数,下同)用两种方法制备的样品其衍射峰逐渐增强。这表明,添加CeO2促进了该体系磷酸盐玻璃的结晶。但是,继续提高CeO2含量至1.5%,衍射峰的强度降低。
图1
图1
磷酸盐微晶玻璃的XRD谱
Fig.1
XRD plots of the phosphate glass-ceramics made by melting method (a) and sintering method (b)
用两种方法制备的微晶玻璃的微观形貌,如图2所示。图2a~D给出了用熔融制备的微晶玻璃在CeO2含量为0~1.5%时的微观形貌。未添加CeO2样品(图2a)内的颗粒呈树杈状零星分布在玻璃基体中,颗粒边界粗糙且模糊。随着CeO2含量提高到1%微晶玻璃内颗粒的边界逐渐清晰,呈等轴状的趋势发育,晶粒的尺寸逐渐减小,排列更加致密。当CeO2含量提高到1.5%时颗粒尺寸和长径比增大,颗粒交错排列呈网络状,孔隙明显地分布在颗粒之间。图2a~d给出了用烧结法制备的CeO2含量为0~1.5%微晶玻璃的微观形貌。可以看出,在未添加CeO2的(图2a)样品内可见平均尺寸为1~2 μm的球状颗粒,颗粒间的界面较模糊。结合其XRD谱可见,该样品的结晶度较低,其中的球状颗粒可能是烧结时未完全结晶的玻璃粉。随着CeO2添加量的提高材料内颗粒的轮廓逐渐清晰。随着CeO2的含量提高到0.5%逐渐生成尺寸较大形状不规则的晶粒(图2b),但是仍有少量细小的圆球状颗粒。在CeO2添加量达到1%的样品内出现显著的片状颗粒,圆球状颗粒完全消失。继续提高CeO2含量到1.5%则微晶玻璃内的片状颗粒团聚成更大尺寸不规则的块状颗粒,颗粒间有明显的孔隙,结构变得疏松。
图2
图2
磷酸盐微晶玻璃的SEM照片
Fig.2
SEM graphs of the phosphate glass-ceramics made by melting method with CeO2 addition of 0 (A), 0.5% (B), 1% (C), 1.5% (D), and by sintering method with CeO2 addition of 0 (a), 0.5% (b), 1% (c), 1.5% (d). % represents mole fraction
图3
图3
用熔融法和烧结法制备的磷酸盐微晶玻璃的体积密度、显微维氏硬度和努氏硬度
Fig.3
Bulk density, micro-Vickers hardness and Knoop hardness of the phosphate glass-ceramics made by melting method (a) and sintering method (b)
图4给出了用熔融法和烧结法制备的微晶玻璃的介电常数与介电损耗随频率的变化。可以看出,介电常数和介电损耗均随着频率的升高而降低,尤其是在低频区。根据电介质理论,电介质的介电常数是电子位移极化、离子位移极化、偶极子转向极化和空间电荷极化四种极化方式的贡献[15]。在低频段介电常数主要由空间电荷极化和偶极子转向极化贡献,而在高频段因空间电荷与偶极子转向跟不上频率变化介电常数只是电子位移极化和离子位移极化的贡献。本文用两种方法制备的样品其介电常数频率特征符合Maxwell-Wagner型极化,即当频率升高时极化降低。根据Koop唯象理论,在低频段微晶玻璃电介质中的空间电荷极化起主导作用[16]。随着CeO2添加量从0增加到1%,用两种方法制备的微晶玻璃电介质其介电常数都逐渐升高,然后随着CeO2含量的继续提高而降低。介电常数的升高,可能是CeO2的添加促进了样品结晶引起的。随着CeO2含量的继续提高介电常数降低,可能是CeO2含量超过1%时结晶程度降低所致,这由图1可以看出。
图4
图4
用熔融法和烧结法制备的磷酸盐微晶玻璃的介电常数与介电损耗的频率曲线
Fig.4
Frequency dependent curves of the dielectric constant and dielectric loss of the phosphate glass-ceramics made by melting method (a) and sintering method (b)
图5给出了用熔融法和烧结法制备的微晶玻璃的极化曲线和储能行为。可以看出,用熔融法制备的未添加CeO2样品在场强加到4.5 kV/mm时便击穿。其原因是,内部树枝状且边缘粗糙的颗粒使局部电荷集中[18]。随着CeO2添加量的提高微晶玻璃能承受的场强也显著提高,尤其是CeO2添加量超过1%时击穿场强均在9 kV/mm以上。电介质的击穿场强(即最高工作场强)受内部晶粒尺寸、排布、孔隙、样品外形、尺寸、粗糙度、电极等多种因素的影响,而內部结构的影响尤其重要[19~21]。电介质致密度的提高将整体改善其电学性能,包括提高击穿场强[22,23]。图2给出了用熔融法制备的添加CeO2的微晶玻璃,可见其晶粒细化并排列致密化。正是结构的致密化使添加CeO2的微晶玻璃工作场强显著提高。从图5a还可以看出,CeO2添加量为1%的微晶玻璃其剩余极化强度为0.12 μC/cm2,饱和极化强度为0.51 μC/cm2。添加量为1.5%时剩余极化强度升高到0.15 μC/cm2,而饱和极化强度却降低到0.47 μC/cm2。图5b给出了用熔融法制备的样品的能量释放密度曲线。可以看出,能量释放密度与应用场强之间有非线性关系。CeO2添加量为1%的微晶玻璃样品,在场强为9 kV/mm时能量释放密度最高(13.5 mJ/cm3),是较高饱和极化强度、较低剩余极化强度和较高的应用场强的共同贡献。图5c给出了用熔融法制备的样品的储能效率随场强的变化。可以看出,在最高场强为9 kV/mm、CeO2添加量为1%的微晶玻璃其储能效率最高(50.1%)。用烧结法制备的微晶玻璃样品,具有高损耗型电滞回线[24]。图5a也表明,CeO2的加入使工作场强的提高。从图5b可以看出,CeO2添加量为1%用烧结法制备的微晶玻璃样品具有最高的能量释放密度(22.5 mJ/cm3)。虽然此值高于其他体系磷酸盐微晶玻璃,但是与硅酸盐体系微晶玻璃材料相比还有较大的差距[25,26]。图5c给出了用烧结法制备的样品的储能效率随场强的变化。可以看出,尽管CeO2添加量为1%的样品表现出极高的储能效率水平,但是最高场强为9 kV/mm时其储能效率只有27.3%。
图5
图5
用熔融法和烧结法制备的磷酸盐微晶玻璃的极化曲线、能量释放密度与能量效率
Fig.5
P-E hysteresis loops, discharged energy density, energy efficiency of the phosphate glass-ceramics made by melting method (A~C) and sintering method (a~c)
有机电介质即聚合物基电介质具有较高的击穿场强(>400 kV/mm)、较低的介电损耗(<0.01)、较高的储能效率(>60%),但是其介电常数水平很低(<5),且易老化变质[27,28]。无机电介质材料的介电常数较高(>30)且范围可调,但是其击穿场强(<15 kV/mm)较低和介电损耗(>0.05)较高[29,30]。微晶玻璃是一种新型复合材料,其内部的无孔隙玻璃相击穿场强较高,内部的高极化铁电晶体相的介电常数较高。这表明,介电微晶玻璃兼具高介电常数和高击穿场强的潜质。但是界面效应和制备过程中引起微观结构不均匀性,其内部大量玻璃相和晶体相界面引起的空间电荷使局部电荷集中而降低了整体的击穿场强,从而限制了微晶玻璃电介质整体的储能行为。
用于储能电容器的微晶玻璃电介质,目前主要是硅酸盐玻璃基,磷酸盐玻璃基微晶玻璃报道较少,目前只有Bih L.组作了相关报导[25,26,33]。表1列出了目前基于两种玻璃体系的介电微晶玻璃的电学性能。可以看出,硅酸盐玻璃基和磷酸盐玻璃基的微晶玻璃的介电常数普遍较高且范围可调,介电损耗可控制在0.022以内。本文制备的磷酸盐微晶玻璃的介电常数为37~43,介电损耗低于0.02,与表1列出的水平相当。从表1还可以看出,基于硅酸盐微晶玻璃的工作场强普遍高于基于磷酸盐的微晶玻璃,是其能量释放密度也普遍偏高。本文制备的磷酸盐微晶玻璃的最高工作场强和能量释放密度与表1给出的磷酸盐的微晶玻璃的相当,也反映出磷酸盐微晶玻璃的最高工作场强和能量释放密度还有待提高。由于储能效率属于多变量参数,与应用场强和电介质类型有关,场强越大弛豫型(或反铁电型)电介质的储能效率随之提高。磷酸盐体系较低的工作场强使本文制备的微晶玻璃的储能效率受到限制。本文制备的添加CeO2为1%的微晶玻璃储能效率最佳,为50.1%。
表1 用于储能电容器的微晶玻璃的电学性能
Table 1
No. | Glass-ceramic system | εr | tan δ | E /kV·mm-1 | Ud /mJ·cm-3 | η | Ref. |
---|---|---|---|---|---|---|---|
1 | PbO-SrO-Na2O-Nb2O5-SiO2 | 427 | 0.022 | 44.2 | 850 | - | [31] |
2 | BaO-Na2O-Nb2O5-SiO2 | 312 | 0.016 | 16.3 | 370 | 72 | [7] |
3 | BaO-SrO-TiO2-Al2O3-SiO2 | 282 | 0.018 | 26.5 | 178 | 42.3 | [32] |
4 | BaTiO3-glass (BaO-Bi2O3-P2O5) | 1750 | 0.088 | 1.5 | 2.3 | 42.3 | [25] |
5 | BaO-Na2O-P2O5-Nb2O5-WO3 | 38 | 0.021 | 9 | 25.6 | 73.7 | [26] |
6 | NaNbO3-glass (Na2O-Nb2O5- P2O5) | 406 | 0.01 | 6 | 68.4 | 84.8 | [33] |
3 结论
(1) 用熔融法和烧结法制备的P2O5-Nb2O5-BaO-Na2O-CeO2系磷酸盐微晶玻璃,都由BaNb2P2O11和Nb(PO4)O两个结晶相组成。随着CeO2的添加量从0提高到1%微晶玻璃的结晶度逐渐提高,且其内部结构逐渐致密化。
(2) 随着CeO2添加量的提高,用两种方法制备的微晶玻璃的体积密度、显微维氏硬度与努氏硬度随着提高,CeO2添加量为1%时达到最大值。用熔融法制备的样品晶粒细小且排列更致密,使其具有更高的体积密度、显微维氏硬度与努氏硬度。
(3) 采用两种方法制备的微晶玻璃其介电常数与损耗都随着频率的提高快速降低,添加CeO2使样品的介电常数提高和介电损耗降低。
(4) 添加CeO2促进了该体系微晶玻璃的工作场强,测试场强为9 kV/mm时用熔融法制备的样品其CeO2添加量为1%时能量释放密度最高达到13.5 mJ/cm3,储能效率最高达到50.1%。而用烧结法制备的样品其能量释放密度最高达到22.5 mJ/cm3,其储能效率只有27.3%,可归因于其显著的高损耗型电滞回线。
参考文献
Application of glass-ceramics for electronic components and circuits
[J].
Effect of additives on the crystallization kinetics of barium strontium titanate glass-ceramics
[J].
A novel high-strength lithium disilicate glass-ceramic featuring a highly intertwined microstructure
[J].
Investigation of structure, dielectric and energy-storage properties of lead-free niobate glass and glass-ceramics
[J].
Improvement in structural, dielectric and energy-storage properties of lead-free niobate glass-ceramic with Sm2O3
[J].
Preparation and dielectric characterization of lead-free niobate glass-ceramic composites added with Lu2O3
[J].
Optimized structural and mechanical properties of borophosphate glass
[J].
Structural and dielectric properties of K2O-TiO2-P2O5 glass and its associated glass-ceramic
[J].
Raman spectroscopic investigations on UV irradiated phosphate glasses with high content of silver or sodium
[J].
Sintering and mechanical properties of lithium disilicate glass-ceramics prepared by sol-gel method
[J].
Preparation and structural transformation of PbF2·SiO2 based glass ceramics prepared by sol-gel method
[J].
PbF2·SiO2基玻璃陶瓷的溶胶-凝胶法制备及结构转变研究
[J].
Development of preparing bioglass ceramic coatings by sol-gel
[J].
溶胶-凝胶法制备生物玻璃陶瓷涂层的发展
[J].
Low-loss spinel nanoferrite with matching permeability and permittivity in the ultrahigh frequency range
[J].
Comparative study of dielectric behavior of Mn0.4Zn0.6Fe2O4 nanoferrite by citrate precursor method
[J].
Electrical tree characteristics of XLPE under repetitive pulse voltage in low temperature
[J].
Structural and dielectric characterization of Gd2O3-added BaO-Na2O-Nb2O5-SiO2 glass-ceramic composites
[J].
Improved energy storage density in barium strontium titanate by addition of BaO-SiO2-B2O3 glass
[J].
Dielectric strength of fine grained barium titanate ceramics
[J].
Properties of ZnO varistor ceramics Co-doped with B2O3 and Al2O3
[J].
B2O3和Al2O3共同掺杂ZnO压敏陶瓷的性能
[J].
Effect of Cr2O3 addition on the microstructure and electrical properties of SnO2-based varistor
[J].
Dielectric hysteresis measurement in lossy ferroelectrics
[J].
Effect of BaO-Bi2O3-P2O5 glass additive on structural, dielectric and energy storage properties of BaTiO3 ceramics
[J].
Structural, elelectrical and energy storage properties of BaO-Na2O-Nb2O5-WO3-P2O5 glass-ceramics system
[J].
Ultrahigh discharge efficiency in multilayered polymer nanocomposites of high energy density
[J].
Reduction of dielectric hysteresis in multilayered films via nanoconfinement
[J].
Lead-free BaTiO3-Bi(Zn2/3Nb1/3)O3 weakly coupled relaxor ferroelectric materials for energy storage
[J].
Silver niobate lead-free antiferroelectric ceramics: enhancing energy storage density by B-site doping
[J].
Optimization of energy storage density in ANb2O6-NaNbO3-SiO2 (A=[(1-x)Pb, xSr]) nanostructured glass-ceramic dielectrics
[J].
Sintering temperature dependence of energy-storage properties in (Ba, Sr)TiO3 glass-ceramics
[J].
/
〈 |
|
〉 |
