宽带隙、高折射率聚偏四氟乙烯/TiO2-ZrO2光学膜的制备和表征

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张裕卿, 赵丽丽, 许世龙, 张超, 陈笑迎, 宋力昕. 宽带隙、高折射率聚偏四氟乙烯/TiO₂-ZrO₂光学膜的制备和表征 . 无机材料学报, 2013, 28(6): 671-676
ZHANG Yu-Qing, ZHAO Li-Li, XU Shi-Long, ZHANG Chao, CHEN Xiao-Ying, SONG Li-Xin. Preparation and Characterization of Polyvinylidene Fluoride/ZrO₂-TiO₂Optical Film with Wide Band Gap and High Refractive Index . Journal of Inorganic Materials, 2013, 28(6): 671-676 复制到剪切板

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宽带隙、高折射率聚偏四氟乙烯/TiO₂-ZrO₂光学膜的制备和表征

张裕卿¹, 赵丽丽², 许世龙¹, 张超¹, 陈笑迎², 宋力昕²

1. 天津大学化工学院, 天津300072

2. 中国科学院上海硅酸盐研究所, 特种无机涂层重点实验室, 上海201800

摘要

以氧氯化锆(ZrOCl₂·8H₂O)为锆源, 钛酸丁酯(Ti(OBu)₄)为钛源, 聚偏氟乙烯(PVDF)为有机添加剂, 采用溶胶-凝胶法在K9玻璃基片上制备PVDF/TiO₂-ZrO₂光学膜, 提高了ZrO₂-TiO₂光学膜的综合性能。然后采用SEM、FT-IR、接触角以及紫外/可见/近红外透射光谱等手段对PVDF/TiO₂-ZrO₂光学膜的组成、光学性能和抗激光损伤阈值进行了研究。SEM测试表明, 在K9玻璃基片上制备了光学膜。PVDF的添加导致水与薄膜的接触角增大。ZrO₂-TiO₂光学膜的光学带隙随ZrO₂含量的增加而略微增大, PVDF/ZrO₂(50mol%)-TiO₂薄膜的光学带隙随PVDF质量分数的增加而增大。另外, ZrO₂-TiO₂光学膜的折射率随ZrO₂摩尔分数的减小而增大, PVDF/ZrO₂(50mol%)-TiO₂膜的折射率随PVDF质量分数的增加而增大。

关键词: ZrO₂; TiO₂; PVDF; 光学膜

中图分类号:TB34 文献标志码:A 文章编号:1000-324X(2013)06-0671-06

Preparation and Characterization of Polyvinylidene Fluoride/ZrO₂-TiO₂Optical Film with Wide Band Gap and High Refractive Index

ZHANG Yu-Qing¹, ZHAO Li-Li², XU Shi-Long¹, ZHANG Chao¹, CHEN Xiao-Ying², SONG Li-Xin²

1. School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China

2. The key Laboratory of Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, China

Corresponding author: ZHAO Li-Li, professor. E-mail:zll@mail.sic.ac.cn

Abstract

To improve the integrative properties of ZrO₂-TiO₂ optical film, polyvinylidene fluoride (PVDF)/ZrO₂-TiO₂ film was coated on the K9 glass substrate by Sol-Gel method using ZrOCl₂·8H₂O and Ti(OBu)₄as precursor of Zr and Ti, respectively. Using PVDF as organic additive, PVDF/ZrO₂-TiO₂ optical films were characterized by SEM, FT-IR and contact angle. Then the optical properties of the PVDF/ZrO₂-TiO₂ optical films were investigatedviaUltraviolet/ Visible/Near Infrared transmission spectrum, optical band gap (E_g) and refractive index. SEM images indicate that the optical films are successfully prepared on the glass substrates. The addition of PVDF in the optical films increases the contact angle between water and the films.E_g of ZrO₂-TiO₂optical films are slightly widened with the increasing of ZrO₂content, andE_g of PVDF/ZrO₂(50mol%)-TiO₂ films are widened as the mass fraction of PVDF increases. In addition, refractive indexes of ZrO₂-TiO₂ optical films increase as the mole fraction of ZrO₂ decreases, and refractive indexes of PVDF/ZrO₂(50mol%)-TiO₂ films increase as the mass fraction of PVDF increases.

Keyword: ZrO₂; TiO₂; PVDF; optical film

Show Figures

Optical film is an important part of high energy laser system nowadays, so the improvement of the integrative properties of the optical films can promote the broad application of the laser system^{[ 1]}. Traditional physical preparation methods of optical films easily generate chemical defects and compact structure, and can not give optical film with large caliber and irregular shape. They cost highly and the films show poor performance of resistance to laser damage^{[ 2]}. Sol-Gel method is very easy to realize large-scale preparation of the film on the substrates with irregular shapes and different materials^{[ 3]}. The advantages of Sol-Gel method are as follows: the preparation is easy and conducted at low-tempearature^{[ 4]}; the thickness, chemical composition and microstructure of the film are felexible to control; chemical defects can be effectively avoided^{[ 5, 6, 7]}. Therefore, it is of great theoretical and potential interests to develop optical films with excellent optical capabilities by using Sol-Gel method.

For the optical films the higher laser induced damage threshold can be achieved by the wider optical gap. At present, many kinds of optical films with wide optical band gap and high refractive index have been studied. Among these films, ZrO₂ and TiO₂ receive much attention because of their good chemical properties and thermal stability, low absorption and dispersion in the visible and near infrared region, wide optical band gap, high refractive index and some other advantages^{[ 2]}.

Nowadays, ZrO₂ film has been widely investigated. Thomas^{[ 8]} and Floch^{[ 9]} prepared ZrO₂/SiO₂ film with high reflection index via Sol-Gel process. Shen^{[ 10]} prepared ZrO₂filmwith high refractive index by hydrolyzing ZrOCI₂·8H₂O via hydrothermal method. Recently, Oda^{[ 11]}, Pradhan^{[ 12]} and Antonello^{[ 13]} have studied TiO₂film with high reflection. ZrO₂film has high laser induced damage threshold and high light transmittance, but it has low refractive index. On the contrary, TiO₂film has low laser induced damage threshold and low light transmittance, and it has high refractive index. Recently, Liang^{[ 2]} prepared ZrO₂-TiO₂film via Sol-Gel method. By combining the laser induced damage threshold of ZrO₂ with the high refractive index of TiO₂, the ZrO₂-TiO₂ film has fine optical properties and performance of anti-laser-induced damage. However, pure inorganic film has loose film stress and poor compatibility with the substrate. PVDF with good film forming properties and mechanical properties may become additive of optical film to improve the film stress and compatibility with the substrate^{[ 14, 15]}. Consequently, it is proposed to prepare wide optical band gap and high refractive index PVDF/ZrO₂-TiO₂film.

1 Experimental

1.1 Materials

Polyvinylidene fluoride (PVDF, chemical reagent grade), N,N-dimethylacetamide (N,N-DMAc, chemical reagent grade), tetrabutyl titanate (Ti(OBu)₄, chemical reagent grade), absolute ethanol (chemical reagent grade), deionized water (chemical reagent grade), hydrochloric acid ((analytical reagent grade, 0.37wt%), zirconyl chloride octahydrate (ZrOCl₂·8H₂O, chemical reagent grade), K9 optical glass substrate, alkaline washings (chemical reagent grade).

1.2 Preparation process

The K9 optical glass substrate was thoroughly rinsed in the alkaline solution and washed by water. Then it was ultrasonically cleaned in absolute alcohol and deionized water, respectively. Finally, it was dried.

The TiO₂ sol was prepared by adding absolute alcohol, Ti(OBu)₄, deionized water and HCl, with the mole ratio of 25:1.0:4.0:0.75 under magnetic stirring , to a 25 mL glass bottle via stepwise hydrolysis. Then it was stirred for 4 h and aged at room temperature for 24 h.

The ZrO₂ sol was prepared by dissolving a certain amount of ZrOCl₂·8H₂O into absolute alcohol in a 25 mL glass bottle, and the concentration of ZrOCl₂·8H₂O was 1.6 mol/L. The sol was mechanically stirred for 30 min at room temperature, and then heated to 85℃ and kept at 85℃ for 20-25 min. After the reactant was cooled to room temperature, a cream transparent sol was obtained.

The PVDF solution was prepared by dissolving 1 g PVDF in 3.9 mL DMAc under magnetic stirring.

The mixed sol was prepared by mixing TiO₂colloidal solution with ZrO₂ colloidal solution. The mole fraction of ZrO₂ colloidal solution was 40mol%, 50mol%, and 60mol%. The mixture was mechanically stirred for 1 h. The PVDF solvent was dropped in 50mol% ZrO₂ sol to get sol mixture (mass fraction of PVDF in the total sol was 0, 0.1wt% and 0.5wt%).

The film was obtained by coating the sol on the K9 glass via Czochralski method at the pulling rate of 2.0 mm/s. Then it was dried in the air at 25℃ for 5-6 d.

1.3 Characterization

Cross-sections of the films samples were observed under MAGELLAN400, FE-SEM, (FEI Co., USA). The transmittances of the PVDF/ZrO₂-TiO₂ films were measured on CARY500, UV-Vis-Nir spectrophotometer (Varian Co., USA) at 25℃ in the wavelength range of 190- 1100 nm. The refractive indexes of films were measured on GES5E, Variable Temperature Ellipsometer (SOPRA Co., France). Contact angles of the film samples were measured with OCA20 Contact Angle System supplied by Dataphysics Corporation (German). The accuracy of measurements is ±0.1°. A water droplet (2.0 μL) was deposited on the surface of the film with a microliter syringe under a middle speed. Each value was obtained 10s after dropping water on the film surface. FT-IR spectra of the PVDF/ZrO₂-TiO₂ films were recorded on Nexus spectrometer in transmission mode (Thermo Co., USA).

2 Results and discussion

2.1 SEM analysis

Figure 1 showed the cross sections of the films. As shown in Fig. 1, the films were evenly coated on the substrate glasses. The thicknesses of the films were as follows: 178.1, 163.5-184.6, 282.7-287.3, 217, 373.7 nm for ZrO₂(40mol%)-TiO₂, ZrO₂(50mol%)-TiO₂, ZrO₂(60mol%)- TiO₂, PVDF(0.1wt%)/ZrO₂ (50mol%)-TiO₂, PVDF (0.5wt%)/ ZrO₂(50mol%)-TiO₂ films, respectively.

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	Fig. 1 Cross-sectional images of PVDF/ZrO₂-TiO₂ film(a) ZrO₂(40mol%)-TiO₂; (b) ZrO₂(50mol%)-TiO₂; (c) ZrO₂(60mol%)-TiO₂; (d) PVDF(0.1wt%)/ZrO₂(50mol%)-TiO₂; (e) PVDF(0.5wt%) ZrO₂(50mol%)-TiO₂

So it could be concluded that the thickness of the films increased with the increasing of the mole fraction of ZrO₂. The films thickened after the adding of PVDF, and the more PVDF the films contained, the thicker the films were. It should be attributed to the viscosity increasing with the increasing mass fraction of PVDF.

2.2 Contact angle analysis

The contact angles between water and PVDF/ZrO₂(50mol%)-TiO₂ film phases were measured and the results were shown in Fig. 2. It can be observed that when the mass ratios of PVDF are 0.1wt% and 0.5wt%, the contact angles of PVDF/ZrO₂(50mol%)-TiO₂ film reach 99.6° and 105.6°, respectively, while that of pure ZrO₂(50mol%)- TiO₂ film is 97.3°. It is indicated that PVDF is mixed in the pure ZrO₂(50mol%)-TiO₂ film, for PVDF is hydrophobic.

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	Fig. 2 Contact angle images of PVDF/ZrO₂ (50mol%)-TiO₂ film(a) Without PVDF; (b) PVDF (0.1wt%); (c) PVDF (0.5wt%)

2.3 FT-IR Spectrum

In Fig. 3, absorption peak centered at 472 cm^-1 belongs to the Zr-O-Zr stretching vibrations and Ti-O-Ti stretching vibrations^{[ 2, 16]}. The absorption peak of Zr-O stretching vibrations and Ti-O stretching vibrations occurr at 648 cm^{-1[ 2, 16]}. All the spectra give peaks at 1630 cm^-1 corre sponding to the bending vibrations in H₂O molecules^{[ 17]}, which may be generated during polycondensation or absorbed from the air. On the other hand, it can be confirmed that with the mole fraction of ZrO₂ increasing, absorption peak of Zr-O-Zr is strengthened, while peaks belonging to Ti-O-Ti weakened.

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	Fig. 3 FT-IR spectra of ZrO₂-TiO₂film

In Fig. 4, the peaks of Zr-O-Zr and Ti-O-Ti also appear. The presence of PVDF is verified by the C-F stretching vibration peak centered at 1190 cm^-1 and asymmetric C-H stretching vibration peak occurred at 2970 cm^-1 observed on the PVDF/ZrO₂-TiO₂ film. Additionally, the peak centered at 1400 cm^-1 is contributed to C-H stretching vibration. Therefore it can be concluded that PVDF is successfully added in the ZrO₂-TiO₂ film.

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	Fig. 4 FT-IR spectra of PVDF(0, 0.1wt%, 0.5wt%)/ZrO₂(50mol%)-TiO₂ film

By compare, it can be confirmed that C-F stretching vibration peak, asymmetric C-H stretching vibration peak and the C-H stretching vibration peak of PVDF(0.5wt%)/ ZrO₂-TiO₂ film is stronger than that of PVDF(0.1wt%)/ ZrO₂-TiO₂ film. The higher the mass fraction of PVDF is, the stronger the peaks are, which further proves the existence of PVDF in the ZrO₂-TiO₂ film.

2.4 Transmittance spectrum

It can be found in Fig. 5 that the descending order of the transmittance of ZrO₂-TiO₂film is: ZrO₂(60mol%)- TiO₂ film, ZrO₂(50mol%)-TiO₂ film, ZrO₂(40mol%)-TiO₂ film, because the transmittance of ZrO₂ is higher than that of TiO₂^{[ 18]}.

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	Fig. 5 Transmittance spectra of ZrO₂(60mol%)-TiO₂ film, ZrO₂(50mol%)-TiO₂ film and ZrO₂(40mol%)-TiO₂ film

In Fig. 6, the transmittance of pure ZrO₂-TiO₂ film is higher than that of PVDF(0.1wt%)/ZrO₂-TiO₂ film, except for wavelength ranging 586-752 nm; in other ranges of wavelength, the descending order of the transmittance is as follows: pure ZrO₂(50mol%)-TiO₂ film, PVDF(0.1wt%)/ ZrO₂(50mol%)-TiO₂ film, PVDF(0.5wt%)/ ZrO₂(50mol%)-TiO₂ film.

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	Fig. 6 Transmittance spectra of ZrO₂(50mol%)-TiO₂ film, PVDF (0.1wt%)/ZrO₂(50mol%)-TiO₂ film and PVDF(0.5wt%)/ ZrO₂(50mol%)-TiO₂ film

2.5 Band gap analysis

Figure 7 shows the descending order of laser induced damage threshold: ZrO₂(60mol%)-TiO₂ film, ZrO₂(50mol%)-TiO₂ film, ZrO₂(40mol%)-TiO₂film. This is because laser induced damage threshold of ZrO₂is higher than that of TiO₂^{[ 18]}.

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	Fig. 7 ( αh v)^1/2- E curves of the ZrO₂(40mol%, 50mol%, 60mol%)-TiO₂film

Figure 8 shows that laser induced damage threshold of ZrO₂(50mol%) -TiO₂ film increases after being added with 0.1wt% and 0.5wt% PVDF. The descending order of laser induced damage threshold is: PVDF(0.5wt%)/ ZrO₂(50mol%)-TiO₂film, PVDF(0.1wt%)/ZrO₂(50mol%)-TiO₂film, pure ZrO₂(50mol%)-TiO₂ film. Additionally, the rate of increasing is quite slow.

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	Fig. 8 ( αh v)^1/2- E curves of the PVDF(0, 0.1wt%, 0.5wt%)/ZrO₂(50mol%)-TiO₂ film

2.6 Refractive index studies

Figure 9 shows the refractive index of the films ( λ=550 nm), it can be found that the refractive index of the films reduced with the increasing of mole fraction of ZrO₂. The descending order of refractive index is: ZrO₂(40mol%)- TiO₂ film, ZrO₂(50mol%)-TiO₂ film, ZrO₂(60mol%)-TiO₂ film, which is because the light transmittance of ZrO₂ is higher than that of TiO₂. So when the mole fraction of ZrO₂ increases, the light transmittance increases and the refractive index decreases.

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	Fig. 9 The refractive index of ZrO₂(50mol%)-TiO₂ film, PVDF (0.1wt%)/ZrO₂(40mol%)-TiO₂ film, PVDF(0.1wt%)/ZrO₂(50mol%)-TiO₂ film, PVDF(0.1wt%)/ZrO₂(60mol%)-TiO₂ film and PVDF(0.5wt%)/ZrO₂(50mol%)-TiO₂ film

Also, it can be demonstrated that the refractive index of the films increases with the increasing of the mass fraction of PVDF. The descending order of refractive index is PVDF(0.5wt%)/ZrO₂(50mol%)-TiO₂ film, PVDF (0.1wt%)/ZrO₂(50mol%)-TiO₂ film, ZrO₂(50mol%)-TiO₂ film, this is because that PVDF is a semitransparent polymer and its light transmittance is far lower than that of ZrO₂. Therefore, with the increasing of the mass fraction of PVDF, the light transmittance decreases and the refractive index increases.

3 Conclusion

PVDF/ZrO₂-TiO₂ films were successfully prepared on the K9 glass substrate by Sol-Gel method. The addition of PVDF in the optical films increases the contact angle between water and the films. E_g of ZrO₂-TiO₂optical films slightly widened with the increasing of ZrO₂content, and E_g of PVDF/ZrO₂(50mol%)-TiO₂ films widened as the mass fraction of PVDF increases. Refractive indexes of ZrO₂-TiO₂ optical films increase as the mole fraction of ZrO₂ decreases, and refractive indexes of PVDF/ ZrO₂(50mol%)-TiO₂ films increase as the mass fraction of PVDF increases. E_g of PVDF/ZrO₂(50mol%)-TiO₂ film widened from 3.520, 3.528 to 3.548 eV, and refractive index are increased from 1.8721, 1.8986 to 2.9661 with the increasing of the mass fraction of PVDF. Therefore, PVDF/ZrO₂-TiO₂ optical films will have a promising application in the laser system.

参考文献

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2012

2.112

0.0

... Optical film is an important part of high energy laser system nowadays, so the improvement of the integrative properties of the optical films can promote the broad application of the laser system^[1] ...

2007

1.016

1.691

Acta Physica Sinica. 2007, 56(6):3596-3601

Studies on the laser-induced damage resistance of Sol-Gel derived ZrO₂-TiO₂ composite high refractive index films

(1)中国工程物理研究院激光聚变研究中心，绵阳 621900; (2)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原 030001; (3)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原 030001;太原科技大学材料科学与工程学院,太原 030024;中国科学院研究生院,北京 100049; (4)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原 030001;中国科学院研究生院,北京 100049; (5)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原 030001;中国科学院研究生院,北京 100049;中国工程物理研究院激光聚变研究中心，绵阳 621900

ZrO₂-TiO₂ composite films with mol fraction of Ti in the total amount of Zr and Ti ranging from 0 to 100, have been prepared by the sol-gel spin-coating method. The microstructure, optical properties, and laser-induced damage resistance (LIDR) of these films were investigated, and emphasis was given to the compositional dependence of the laser-induced damage threshold (LIDT). The experimental results indicate that at a small expense of refractive index, the sol-gel process can considerably improve the LIDR of the films. Moreover, with increasing mol fraction of Ti from 0 to 100, a general decrease of the LIDT in a wide range of 57.1—20.9J/cm²(at 1053nm，10ns pulse duration and in “R/1” testing mode) was observed. Combining the structural and optical analysis results, a possible correlation between the LIDR and optical band gap of the prepared films is presented on the basis of the multiphoton absorption model.

采用溶胶-凝胶方法制备了ZrO₂-TiO₂(Ti含量为0—100mol%)高折射率光学薄膜. 借助激光动态光散射技术研究溶胶微结构. 采用傅里叶变换红外光谱、原子力显微镜、薄膜光学常数分析仪、漫反射吸收光谱及强激光辐照实验，对膜层的结构、光学性能及抗激光损伤性能进行了系统表征. 结果显示，溶胶-凝胶工艺可以在部分牺牲折射率的情况下，使膜层的抗激光损伤性能得到大幅度提升. 随Ti含量从0mol%增加至100mol%，膜层的平均损伤阈值呈下降趋势，当Ti含量从0mol%增加至60mol%时，平均损伤阈值从57.1J/cm²下降到21.1J/cm²(辐照激光波长为1053nm，脉冲宽度为10ns，“R/1”测试模式)，当Ti含量从60mol%增加至100mol%时，平均损伤阈值变化很小. 综合溶胶微结构、膜层光学性能和损伤实验结果可以推断，强激光诱导多光子吸收是引起膜层损伤的主要原因. 不同配比的复合膜之间光学带隙的显著差异导致相同辐照激光情况下多光子吸收的概率发生变化，从而导致损伤阈值的规律性变化.

... They cost highly and the films show poor performance of resistance to laser damage^[2] ...

... Among these films, ZrO₂ and TiO₂ receive much attention because of their good chemical properties and thermal stability, low absorption and dispersion in the visible and near infrared region, wide optical band gap, high refractive index and some other advantages^[2] ...

... Recently, Liang^[2] prepared ZrO₂-TiO₂film via Sol-Gel method ...

... 3, absorption peak centered at 472 cm^-1 belongs to the Zr-O-Zr stretching vibrations and Ti-O-Ti stretching vibrations^{[2, 16]} ...

... The absorption peak of Zr-O stretching vibrations and Ti-O stretching vibrations occurr at 648 cm^{-1[2, 16]} ...

2012

0.0

... Sol-Gel method is very easy to realize large-scale preparation of the film on the substrates with irregular shapes and different materials^[3] ...

2012

1.789

0.0

... The advantages of Sol-Gel method are as follows: the preparation is easy and conducted at low-tempearature^[4] ...

2012

4.387

0.0

... chemical defects can be effectively avoided^[5,6,7] ...

2012

2.163

0.0

J. Mater. Sci.. 2012, 47(13):5216-5221 DOI:10.1007/s10853-012-6405-3

Phase and structural evolution of Sol-Gel synthesized ZrO₂/Si thin films under heat treatment

<li>1.School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 440-746, Korea</li>

Abstract
ZrO₂/Si thin films were fabricated using a sol–gel technique, and the chemical state change and structural evolution from sol to gel to Zr oxide by heat treatment were investigated. The precursor sol was synthesized using a Zr-acetylacetonate (Zr-acac) precursor, spin-coated, dried on Si(100) substrates, and then annealed at 300–700 °C in air. With increased annealing temperature of the sol–gel-derived layer, Zr-acac decomposed into Zr-acetate, an amorphous ZrO₂ phase formed, and crystallization into a tetragonal phase occurred. In addition, the ZrO₂ layer became denser and the interfacial layer between ZrO₂ and Si thickened, whereas the surface morphology was nearly unaffected and remained smooth with root-mean-square values < 4.5 Å.

... chemical defects can be effectively avoided^[5,6,7] ...

2006

1.016

1.691

Acta Physica Sinica. 2006, 55(11):6175-6183

Sol-Gel deposition of highly reflective multilayer coatings from PVP-ZrO₂ hybrid systems

(1)中国工程物理研究院激光聚变研究中心，绵阳 621900; (2)中国科学院高能物理研究所同步辐射实验室,北京 100049; (3)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原 030001; (4)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原 030001；太原科技大学材料科学与工程学院,太原 030024；中国科学院研究生院,北京 100049; (5)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原 030001；中国科学院研究生院,北京 100049；中国工程物理研究院激光聚变研究中心，绵阳 621900

A series of ZrO₂ and polyvinylpyrrolidone (PVP) doped-ZrO₂ sols have been synthesized by the controlled hydrolysis and condensation of zirconium n-propoxide, with diethanolamine (DEA) as the chelating agent. PVP-ZrO₂ hybrid monolayers and highly reflective (HR) multilayer coatings were then prepared by spin-coating the stable sols on K9 glass substrates. The fabrication of the HR coatings involves alternate depositions of PVP-ZrO₂ (as the high-index material) and SiO₂ (as the low-index material) layers. The microstructures of the sols, the structural and optical properties, as well as the laser damage resistance of the films were thoroughly characterized. By virtue of the small angle X-ray scattering (SAXS) analysis, the sol-gel processing parameters were successfully optimized, endowing the as-prepared films with good optical properties and high laser damage resistance. SAXS studies also offer the possibility to a good knowledge of the microstructure of the sols. In our hybrid system, the unhydrolyzed DEA ligands, which become anchored in the inorganic network, may considerably weaken the effects of PVP on the formation and growth of ZrO₂ particles. Hence, the incorporation of a proper amount of PVP gives rise to negligible change of the sol structure and only a slight variation in refractive index and laser damage resistance of the films. However, at the slight expense of the refractive index and laser damage resistance, the incorporation of PVP can easily alleviate the stress incompatibility between different layers and facilitate the fabrication of the multilayer coatings. As the mass fraction of PVP reaches 15%—20%, a perfect match between different layers can be achieved, which ensures the successful deposition of 21-layer, nearly full-reflection coatings with the minimum transmittance of about 1.6%—2.1% (at 1064nm) and high laser damage threshold of 16.4—18.2J/cm² (at 1064nm, 1ns pulse duration and R/1 mode).

以丙醇锆(ZrPr)为锆源，二乙醇胺(DEA)为络合剂，原位引入聚乙烯吡咯烷酮(PVP)，在乙醇体系中成功地合成了PVP掺杂-ZrO₂溶胶.采用旋涂法在K9玻璃基片上制备了PVP-ZrO₂单层杂化薄膜.用不同掺杂量的PVP-ZrO₂高折射率膜层与相同的SiO₂低折射率膜层交替沉积四分之一波堆高反射膜.借助小角X射线散射研究胶体微结构，用红外光谱、原子力显微镜、紫外/可见/近红外透射光谱、椭圆偏振仪以及1064nm的强激光辐照实验对薄膜的结构、光学和抗激光损伤性能进行表征.研究发现，体系组成的适当配置可以在溶胶稳定的前提下实现ZrPr的充分水解，赋予薄膜良好的结构、光学和抗激光损伤性能.杂化体系中，DEA与ZPr之间强的配合作用大大降低了ZrO₂颗粒表面羟基的活性，使得PVP大分子只是以微弱的氢键与颗粒的表面羟基作用而均匀分散于ZrO₂颗粒的周围，对颗粒的形成和生长无显著影响.因而在实验研究范围内，随PVP含量的增大，PVP-ZrO₂杂化膜层的折射率和激光损伤阈值均无显著变化.但是，薄膜中均匀分布的PVP柔性链可以有效促进膜层应力松弛，显著削弱不同膜层之间的应力不匹配程度、大大方便多层光学薄膜的制备.当高折射率膜层中PVP的质量分数达到15%—20%时，膜层之间良好的应力匹配使得多层高反射膜的沉积周期数可达到10以上.沉积10个周期的多层反射膜，在中心波长1064nm处透射率约为1.6%—2.1%，接近全反射特征，其激光损伤阈值为16.4—18.2J/cm²(脉冲宽度为1ns).

... chemical defects can be effectively avoided^[5,6,7] ...

1992

1.689

0.0

... Thomas^[8] and Floch^[9] prepared ZrO₂/SiO₂ film with high reflection index via Sol-Gel process ...

1994

0.0

... Thomas^[8] and Floch^[9] prepared ZrO₂/SiO₂ film with high reflection index via Sol-Gel process ...

2000

0.0

J. Sol-Gel Sci. Technol.. 2000, 19(1/2/3):271-274 DOI:10.1023/A:1008761010781

Sol-Gel processing of zirconia coating for HR mirrors with high laser damage threshold

1.Pohl Institute of Solid State Physics Tongji University Shanghai 200092 P.R. China

High laser-damage resistant coatings are very important in high power laser systems. In this study ZrO₂ thin films are prepared by sol-gel spin-coating technology from suitable zirconia aqueous colloidal suspensions containing nano-crystalline ZrO₂ at room temperature synthesized by a hydrothermal process from an inorganic precursor (ZrOCl₂·8H₂O). By adding a soluble organic binder PVP to the suspension prior to application, it is possible to substantially increase the coating refractive index and the abrasion-resistance as well as the laser damage threshold. The features of the coatings and the colloidal suspensions are investigated. Multilayer highly reflective dielectric coatings are also elaborated by applying quarterwave-thick alternating coatings of the binder-aided zirconia and silica, which is prepared with the sol-gel process from TEOS. To achieve 99% reflectivity, 19–21 layers are required. Single shot laser damage tests are carried out using a high power laser at 1064 nm wavelength with a pulse duration of 2.5 ns. The laser damage thresholds of 18 and 15 J/cm² are achieved for single ZrO₂-PVP coating and ZrO₂-PVP/SiO₂ multilayers respectively.

... Shen^[10] prepared ZrO₂filmwith high refractive index by hydrolyzing ZrOCI₂#cod#x000b7 ...

2012

0.0

J. Sol-Gel Sci. Technol.. 2012, 61(3):484-493 DOI:10.1007/s10971-011-2649-7

Sol-Gel-derived titania- hydroxypropylcellulose hybrid thin films of high refractive indices: solution components affecting the refractive index and uncracking critical thickness

<li>1.Graduate School of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, 564-8680, Japan</li><li>2.Faculty of Chemistry and Bioengineering, Kansai University, 3-3-35 Yamate-cho, Suita, 564-8680, Japan</li>

Abstract
Optically transparent, ca. 200–800 nm thick TiO₂-hydroxypropylcellulose (HPC) hybrid thin films were prepared from Ti(OC₃H₇ⁱ)₄–HPC–HCl–H₂O–C₃H₇ⁱOH solutions by the sol–gel method, where the as-deposited films were dried at 120 °C. The effects of the amount of HPC, H₂O and HCl in the starting solutions on the refractive index and uncracking critical thickness of the films were studied, where the effects on the critical thickness was discussed on the basis of in situ stress measurements during heating. The increase in HPC content increased the critical thickness and lowered the refractive index. The increase in HCl content resulted in a decrease in critical thickness and an increase in refractive index. Larger H₂O contents gave rise to a maximum in critical thickness while the refractive index was unaffected. Such variation in critical thickness with varying solution compositions was demonstrated to result from the differences in in-plane stress generated during heating. By optimizing the processing parameters an 810 nm thick TiO₂–HPC hybrid film of a refractive index of 1.84 was obtained.

... Recently, Oda^[11], Pradhan^[12] and Antonello^[13] have studied TiO₂film with high reflection ...

2012

1.604

0.0

... Recently, Oda^[11], Pradhan^[12] and Antonello^[13] have studied TiO₂film with high reflection ...

2011

2.175

0.0

J. Nanopart. Res.. 2011, 13(4):1697-1708 DOI:10.1007/s11051-010-9923-4

Nanocomposites of titania and hybrid matrix with high refractive index

1.INSTM, Dipartimento di Ingegneria Meccanica Settore Materiali, Università di Padova, via Marzolo 9, 35131 Padova, Italy 2.CNISM, Dipartimento di Fisica, Università di Padova, via Marzolo 8, 35131 Padova, Italy 3.TASC – CNR-INFM at ELETTRA-Sincrotrone Trieste, S.S. 14, km 163.5 in Area Science Park, Basovizza, 34017 Trieste, Italy 4.Dipartimento di Fisica, Università di Padova, via Marzolo 8, 35131 Padova, Italy

A sol–gel route for TiO₂ nanocrystals (NCs) synthesis has been developed at low temperature without surfactants. Synthetic and processing parameters have been optimized to maximize particles’ colloidal stability and crystallinity. The obtained TiO₂ NCs can be homogeneously dispersed in a sol–gel derived organic–inorganic hybrid material, resulting in homogeneous composite films when prepared by spin coating. High refractive index films were obtained with high TiO₂ NCs loading and good transparency. Furthermore, TiO₂ colloidal solutions can be used for depositing porous crystalline films, whose structural evolution has been followed under different annealing treatments. Nanocrystals were characterized by UV–Vis absorption, TEM, FT-Raman, and XRD techniques, while nanocomposite and TiO₂ films were analyzed by SEM, TEM, and spectroscopic ellipsometry.

... Recently, Oda^[11], Pradhan^[12] and Antonello^[13] have studied TiO₂film with high reflection ...

2011

3.172

0.0

... PVDF with good film forming properties and mechanical properties may become additive of optical film to improve the film stress and compatibility with the substrate^[14,15] ...

2012

1.395

0.0

... PVDF with good film forming properties and mechanical properties may become additive of optical film to improve the film stress and compatibility with the substrate^[14,15] ...

2010

1.365

0.0

Opt. Laser. Technol.. 2010, 42(8):1187-1192 DOI:10.1016/j.optlastec.2010.03.008

The effect of porosity on the laser induced damage threshold of TiO₂ and ZrO₂ single layer films

Abstract

Monolayer ZrO₂ and TiO₂ films were prepared on BK7 glass by physical vapor deposition (PVD) and were subsequently annealed for 1 h at 300 °C. By using the transmission spectra of two samples and the envelope method, the refractive index dispersion and extinction coefficients have been calculated. Laser induced damage threshold (LIDT) measurement shows that despite slight differences between the extinction coefficients of the two samples, the LIDT parameter of the ZrO₂ film is greater than that of the TiO₂ film. This fact leads us to consider thermal conductivity as an important parameter for interpreting the LIDT difference. According to our theoretical analysis, as a consequence of increase in the number of thermal barriers along poorer film, its thermal conductivity, and hence LIDT, decreased, which is in agreement with our experimental results. The measured porosity of the two samples shows higher porosity for TiO₂ single layer, which is in agreement with atomic force (AFM) images. The gradual and smooth damage morphology of ZrO₂ observed in optical images implies higher thermal conductivity than TiO₂.

... 3, absorption peak centered at 472 cm^-1 belongs to the Zr-O-Zr stretching vibrations and Ti-O-Ti stretching vibrations^{[2, 16]} ...

... The absorption peak of Zr-O stretching vibrations and Ti-O stretching vibrations occurr at 648 cm^{-1[2, 16]} ...

2001

1.597

0.0

... All the spectra give peaks at 1630 cm^-1 corre sponding to the bending vibrations in H₂O molecules^[17], which may be generated during polycondensation or absorbed from the air ...

2012

3.141

0.0

... 5 that the descending order of the transmittance of ZrO₂-TiO₂film is: ZrO₂(60mol%)- TiO₂ film, ZrO₂(50mol%)-TiO₂ film, ZrO₂(40mol%)-TiO₂ film, because the transmittance of ZrO₂ is higher than that of TiO₂^[18] ...

... This is because laser induced damage threshold of ZrO₂is higher than that of TiO₂^[18] ...