【作者】 张洋洋；

【导师】 姜胜林；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2012， 博士

【摘要】 复合热释电材料采用陶瓷与聚合物两相复合而成,兼具陶瓷热释电系数大和聚合物相对介电常数低、具有柔性的优点,是目前热释电材料研究中的热点。为了解决复合热释电材料用于热释电探测器阵列遇到的热释电性能差、界面相容性差、陶瓷极化率低等问题,本文从热释电陶瓷功能相体系的选择、聚合物基体PVDF的改性、复合热释电材料界面的修饰、复合材料中陶瓷功能相的极化四个方面对复合材料进行了系统研究,并在此基础上利用复合材料制备温度低(约100℃)的优点,探讨并制备了基于聚酰亚胺柔性基板的复合热释电膜,设计了一种新型热释电探测器结构,为非制冷红外探测器的制备奠定了基础。针对目前复合热释电材料性能较差的问题,本文对复合材料陶瓷相体系进行了选择。通过理论分析,复合热释电材料中所用陶瓷功能相需满足相对介电常数低、热释电系数高、压电常数小等条件；在实验室前期研究的基础上,通过对锆钛酸铅(PZT)(Pb[(Mn1/3Nb2/3)1/2(Mn1/3Sb2/3)1/2]0.04(ZrxTi1-x)0.96O3)含铅体系及铌酸钠钾(KNN)无铅体系0.95(KxNa1-x)NbO3-0.05LiSbO3进行对比研究,发现与KNN热释电陶瓷体系相比,PZT陶瓷具有较低的相对介电常数、较大的热释电系数、较小的压电常数,因此在本论文中选取PZT系列Zr含量为0.95时的热释电陶瓷为复合材料陶瓷功能相。为了解决基体PVDF相对介电常数小、电导率低的问题,本文通过添加蒙脱土(MMT)、石墨烯微片,研究了不同蒙脱土、石墨烯微片含量对PVDF相结构及性能的影响,探索了β相PVDF形成机理、电导率的变化规律以及压电和热释电性能的产生机理。研究发现MMT的加入诱导了β相PVDF的生成,增加了PVDF的结晶度,提高了PVDF的相对介电常数,其中当MMT含量为2wt%时,67%的PVDF形成了结晶相,相对介电常数增大到9.54,在36℃时热释电系数达到了51μC/m2℃,探测率优值约为0.8×10-5Pa-0.5；采用超声剥离的方法制备了25nm左右厚度的石墨烯微片,复合材料中石墨烯微片的加入在诱导p相PVDF生成的同时增加了PVDF的结晶度,增大了基体的电导率及相对介电常数,并产生了压电和热释电性能,当在制备过程中加入6mL石墨烯微片溶液时,PVDF的结晶度为75%左右,电导率为1.24×10-13S×cm-1,相对介电常数增大到10,在36℃时热释电系数约为54μC/m2℃,探测率优值均值在0.64×10-5Pa-0.5。针对复合热释电材料中陶瓷相和基体相之间界面相容性差的问题,本文通过添加硅烷偶联剂KH570、钛酸酯偶联剂T1-9、螫合剂EDTA来改善复合材料的界面及性能。研究了不同界面修饰剂对复合材料界面、结晶度、击穿场强、介电、压电和热释电性能的影响。研究发现随着KH570、T1-9、EDTA的添加,界面修饰剂在陶瓷粉体与基体之间形成“桥键”结构,改善复合材料界面的同时,诱导生成了β相PVDF,增加了复合材料结晶度,同时增加了基体PVDF的相对介电常数。适量界面修饰剂的增加提高了复合材料陶瓷相的局部电场,使陶瓷相极化充分,提高了复合材料的压电和热释电性能。研究结果表明,当添加0.3wt%钛酸酯偶联剂T1-9时复合材料在界面改善的同时,热释电性能最优,复合材料的热释电系数和探测率优值整体最大,在36℃时分别达到了95.0μC/m2℃和1.24×10-5Pa-0.5。基于解决复合材料中陶瓷相极化的问题,本文通过添加纳米碳粉、碳纳米管导电相,研究了不同导电相含量对复合材料电导率、比热容、介电、压电和热释电性能的影响。研究发现随着导电相的增多,复合材料的电导率逐渐增大并最终达到渗流阈值,同时随着导电相的增多,复合材料的比热容逐渐减小,相对介电常数和介电损耗都逐渐增大,复合材料的压电和热释电性能都出现先增大后减小的趋势。当碳纳米管含量为0.9wt%时,复合材料的热释电性能最优,其热释电系数均值超过130μC/m2℃,探测率优值也高于未掺杂复合材料,在36℃时分别达到了138.68μC/m2℃和1.63×10-5Pa-0.5。最后利用复合热释电材料的制备温度低(约100℃)的优势,探讨并制备了基于聚酰亚胺柔性基板的复合热释电膜阵列,研制了一种新型的非制冷红外探测器结构。本文采用直写、激光微覆熔、激光打孔、丝网印刷等工艺,得到以聚酰亚胺为绝热层,底电极通过通孔连接到背面走线的新型非制冷红外探测器结构。新型的非制冷红外探测器结构在增大热释电探测率的同时,使底电极走线与底电极阵元处于不同的平面,可增加单位面积内阵元的数目,为小尺寸、多阵元探测器的大规模制备奠定了基础。更多还原

【Abstract】 The pyroelectric composite materials which are based on ceramic and polymer and have the merit of ceramic and polymer, is the research hotspot in pyroelectric materials. Pyroelectric composite materials have low pyroelectric property, poor interface bonding and low polarizability of ceramic phase. In order to solve the problem, this thesis conducted a systematic research on choice of ceramic phase, improving of PVDF, modifying of interface, and the polarization of ceramic phase in composite materials. Then a new type of uncooled infrared detectors with polyimide substrate as the thermal isolation structure was prepared. The arrays were made by pyroelectric composite materials which have a low preparation temperature, which layed a basis for the development of uncooled infrared detectors.Concerning on the problem that pyroelectric composite materials have poor properties, the ceramic phase was studied. By theoretical analysis, we found that the ceramic used in composite materials should have lower dielectric constant, larger pyroelectric coefficient and smaller piezoelectric coefficient. On the basic of laboratory study, The ceramic of Pb[(Mn1/3Nb2/3)1/2(Mn1/3Sb2/3)1/2]o.04(ZrxTi1-x)o.9603 and 0.95(KxNa1-x)NbO3-0.05LiSbO3 was investigated and compared. The results showed that the PZT ceramics have lower dielectric constant, larger pyroelectric coefficient and smaller piezoelectric coefficient. So in the study the PZT ceramic was used as the ceramic phase in pyroelectric composite materials when x was 0.95.For the solution of the problem that PVDF has lower dielectric constant and conductivity, the montmorillonite (MMT) and graphite nanosheets (GNS) was added. The impact of MMT and GNS content on the phase transformation, conductivity, pyroelectric property formation mechanisms were discussed. The results showed that with the addition of MMT, the beta phase was induced, the crystallinity and dielectric constant was increased. When the content of MMT was 2wt%, the composite materials have large crystallinity and dielectric constant,67% and 9.54, respectively. The pyroelectric coefficient and figure of merit of detectivity of the composites were reached to 51.0μC/m2℃and 0.8×10-5Pa-0.5 respectively at 36℃. The GNS was made by solution casting method with the thickness of 25nm. With the addition of GNS, the beta phase was induced, the crystallinity, dielectric constant and conductivity was increased. When the content of GNS was 6mL being preparation, the composite materials have a large crystallinity, dielectric constant and conductivity,75%,10 and 1.24×1013S×cm-1, respectively. The pyroelectric coefficient and figure of merit of detectivity of the composites was reached to 54.0μC/m2 and 0.64×10-5Pa-0.5 respectively at 36℃.With a view to solve the problem that the interface bonding between ceramic phase and matrix was poor, the silane coupling agent KH570, titanate coupling agent T1-9 and chelating agent EDTA were added to improve the interface and property. The impacts of interfacial modifier content on the interface, crystallinity, breakdown strength, dielectric, piezoelectric and pyroelectric properties were discussed. The results revealed that with the addition of interfacial modifier, the interface was improved, the beta-PVDF was induced, the crystallinity and dielectric properties was increased. With the proper content of interfacial modifier, the piezoelectric and pyroelectric properties were increased. When the content of titanate coupling agent T1-9 was 0.3wt%, the composite materials have a large pyroelectric coefficient and figure of merit of detectivity,95.0μC/m2℃and 1.24×10-5Pa-0.5, respectively at 36℃.In order to solve the problem that the ceramic in composite materials was difficult to be polarized, the nano carbon and carbon nanotube was added. The impacts of conductive phase on the conductivity, specific heat, dielectric property, piezoelectric property and pyroelectric property were discussed.Experiments indicated that the conductivity and dielectric properties was increased and the specific heat was decreased with the increase of conductive phase, and finally the conductivity reached percolation threshold. The piezoelectric and pyroelectric properties increased with the increase of conductive phase, and then dropped with further increase. These results indicated that when the content of nano carbon was 0.9wt%, the composite materials possessed enhanced pyroelectric properties, with the average of pyroelectric coefficient was exceed 130μC/m2℃, and the pyroelectric coefficient and the figure of merit of detectivity was 138.68μC/n2℃, 1.63 x 10-5Pa-0.5 respectively at 36℃. Finally, a new type of uncooled infrared detectors with polyimide substrate as the thermal isolation structure was prepared. The arrays were made by pyroelectric composite materials which have a low preparation temperature. The bottom electrode and back electrode leader were prepared on the polyimide substrate by direct-writing. Then the bottom electrode and back electrode leader was connected via hole by laser micro cladding technology. Finally, the pyroelectric composite materials and top electrode were prepared by screen-printing technology on the bottom electrode. The new uncooled infrared detectors structure which made the bottom electrode and back electrode leader at different plane of polyimide, could increase the figure of merit of detectivity and the number of array in unit area, and thus laying a basis for small size and multi-elements based uncooled infrared detectors.更多还原