Y和YF3掺杂钛酸钡系PTCR材料的结构及性能

在不同烧结气氛下制备了Ｙ和ＹＦ_３掺杂钛酸钡材料,借助于ＸＲＤ、ＳＥＭ、ＸＲＦ和阻温测试分析仪,研究了烧结气氛对Ｙ和ＹＦ_３掺杂钛酸钡材料结构和性能的影响．研究结果表明,低氧分压气氛可促进Ｙ和ＹＦ_３掺杂钛酸钡材料的烧结,晶粒长大,而且这二种掺杂钛酸钡材料都是ｎ型半导体．经过氩气气氛烧结的Ｙ掺杂钛酸钡材料ＰＴＣＲ效应较弱;而对在氩气气氛中烧结的０．３ｍｏｌ％ＹＦ_３掺杂钛酸钡材料却观察到了较好的ＰＴＣＲ效应,这种效应的产生可能与Ｆ元素取代Ｏ位而导致材料的价控半导有关．     

YF3掺杂钛酸钡半导体材料特性研究

在不同气氛下制备了ＹＦ３掺杂钛酸钡材料,并对其电阻的正温度系数特性进行了研究。借助于ＸＲＤ、ＳＥＭ、ＸＲＦ、阻温特性测试仪和阻抗分析仪,研究了不同处理气氛对ＹＦ３掺杂肽到钡材料结构和性能的影响。研究结果表明,在空气和在氩气中烧结的ＹＦ３掺杂钛酸钡材料都是Ｎ型半导体,其中Ｙ取代Ａ位,Ｆ取代Ｏ位,并对在氢气氛中烧结的ＹＦ３掺杂钛酸钡材料还观察到了不同的ＰＴＣＲ效应。这种ＰＴＣＲ效应的产生可能是由于存在新的取代机制－－Ｏ位取代的半导化机制引起的。     

掺杂V2O3素PTC陶瓷中金属相的研究

报导在掺杂Ｖ２Ｏ３系ＰＴＣ陶瓷中引入Ｆｅ金属相，采用ＸＲＤ，ＳＥＭ分析技术确定Ｆｅ金属相在材料中的结构状态，并结合材料ＰＴＣ性能测试结果讨论了Ｆｅ金属相对材料烧结性能和ＰＴＣ性能的影响。     

掺杂V_2O_3系PTC陶瓷中金属相的研究

报导在掺杂Ｖ＿２Ｏ＿３系ＰＴＣ陶瓷中引入Ｆｅ金属相，采用ＸＲＤ，ＳＥＭ分析技术确定Ｆｅ金属相在材料中的结构状态，并结合材料ＰＴＣ性能测试结果讨论了Ｆｅ金属相对材料烧结性能和ＰＴＣ性能的影响。     

BaTiO_3基PTCR陶瓷中B_2O_3蒸汽掺杂的异常行为

钛酸钡基半导化陶瓷中的ＰＴＣＲ效应通常与材料中的施受主掺杂密切相关．在高温下Ｂ２Ｏ３具有较高的蒸汽压,通过Ｂ２Ｏ３蒸汽掺杂的研究表明,含主族元素Ｂ的氧化物蒸汽掺杂,钛酸钡基半导化陶瓷样品的升阻比同样得到了大幅度提高,同时室温电阻率也有所增加．Ｂ２Ｏ３蒸汽掺杂ＢａＴｉＯ３基材料的ＰＴＣＲ效应的提升可能得益于硼填隙和钡缺位相关的复合缺陷在晶界上的形成．     

Y（NO3）3掺杂BaTiO3半导体材料特性研究

本文研究了以Ｙ（ＮＯ３）３作为施主掺杂元素制备的ＰＴＣＲ材料的显微结构和宏观性能。指出施主以水溶性化合物形式引入制备的ＰＴＣＲ材料，其性能明显优于常规的施主以氧化物形式引入而得到的材料的性能。     

Sr0.4Pb0.6TiO3基陶瓷晶界组成对热敏特性的影响

采用固相烧结工艺制备出了Ｓｒ_０．４Ｐｂ_０．６ＴｉＯ_３半导体陶瓷元件,其阻温特性具有独特的ＮＴＣＲ和ＰＴＣＲ复合效应,陶瓷室温电阻率及居里点以下的ＮＴＣＲ效应随着烧结温度的升高而提高,适当过量ＰｂＯ则能降低陶瓷室温电阻率及其ＮＴＣＲ效应．利用ＸＲＤ、ＳＥＭ和ＥＤＳ分别对样品的相结构、形貌及成份分布等进行分析,结果显示晶界中的Ｓｒ,Ｔｉ含量相对较高,而Ｐｂ含量相对较低,材料的阻温特性明显受其影响．铅挥发造成的阳离子空位是该类半导体陶瓷在居里点下出现ＮＴＣＲ效应的主要原因之一,同时探讨了Ｙ^３＋离子掺杂（Ｓｒ,Ｐｂ）ＴｉＯ_３陶瓷的半导化机理和热敏特性．     

Sol—Gel法制备Y系高温超导材料及烧结条件的研究

介绍了ＹＢａ２Ｃｕ３Ｏ７－δ和Ｆ掺杂的ＹＢａ２Ｃｕ３Ｆ０．６Ｏ７－δ高Ｆｃ超导材料的Ｓｌｏ－Ｇｅｌ法制备，并对烧结条件进行了研究。     

高容量SiO2掺杂的（Ba,Pb）TiO3基高居里温度PTCR陶瓷

在制备高质量的（Ｂａ，Ｐｂ）ＴｉＯ＿３基高居里温度ＰＴＣＲ陶瓷时，一般采用铅气氛烧结方法。但是，这种烧结工艺制成的产品的相对成本是高的。作者的实验表明，高容量ＳｉＯ＿２掺杂烧结方法也可以用于制备高质量的（Ｂａ，Ｐｂ）ＴｉＯ＿３基高居里温度ＰＴＣＲ陶瓷。本文主要报道高容量ＳｉＯ＿２对（Ｂａ，Ｐｂ）ＴｉＯ＿３基高居里温度ＰＴＣＲ陶瓷烧结工艺和电特性的影响。     

TiO2对Y掺杂PTCR陶瓷材料性能的影响

本文对ＴｉＯ２原料的晶型、颗粒状况和纯度对Ｙ＾３＋掺杂ＢａＴｉＯ３基ＰＴＣＲ材料的显微结构、电性能的影响作了探讨，结果表明，ＴｉＯ２原料的晶型、颗粒大小和团聚状况都将影响到ＰＴＣＲ陶瓷的显微结构，ＴｉＯ２原料的晶型对ＰＴＣＲ陶瓷半导化过程有影响，原料存在杂质和团聚，将使ＰＴＣＲ陶瓷的电阻－温度特性变差。     

Effects of reducing and oxidizing atmospheres on the PTCR characteristics of porous n-BaTiO3 ceramics by adding polyethylene glycol

Donor doped BaTiO₃ (n-BaTiO₃) ceramics were fabricated by adding polyethylene glycol (PEG) at 20 wt %. The effects of reducing and oxidizing atmospheres on the PTCR characteristics of the porous n-BaTiO₃ ceramics were investigated. The PTCR characteristics of the porous n-BaTiO₃ ceramics is strongly affected by chemisorbed oxygen at the grain boundaries and are recovered as the atmosphere is changed from the reducing gas to oxidizing gas. The low room-temperature resistivity of the porous n-BaTiO₃ ceramics in reducing atmospheres may be caused by the decrease in potential barrier height, which originates from an increase in the number of electrons owing to the desorption of chemisorbed oxygen atoms at the grain boundaries. In addition, the high room-temperature resistivity of the porous n-BaTiO₃ ceramics in oxidizing atmospheres may be caused by the increase in potential barrier height, which results from the adsorption of chemisorbed oxygen atoms at the grain boundaries.     

BaTiO3基PTCR陶瓷中B2O3蒸汽掺杂的异常行为

钛酸钡基半导化陶瓷中的PTCR效应通常与材料中的施受主掺杂密切相关。在高温下B2O3具有较高的蒸汽压,通过B2O3蒸汽掺杂的研究表明,含主族元素B的氧化物蒸汽掺杂,钛酸钡基半导化陶瓷样品的升阻比同样得到了大幅度提高,同时室温电阻率也有所增加。B2O3蒸汽掺杂BaTiO3基材料的PTCR效应的提升可能得益于硼填隙和钡缺位相关的复合缺陷在晶界上的形成。     

Mn掺杂BaTiO3基PTCR陶瓷相变的EPR研究

为了探索利用EPR谱线对PTCR陶瓷相变及PTC效应的机制研究的可能性,本文对掺Mn的BaTiO3基正温度系数热敏电阻（简称PTCR）陶瓷在120-450K温度范围内的电子顺磁共振谱进行了研究。得于了Mn^2 离子EPR信号强度、g因子值和超精细耦合常数|A|值的温度分布,发现EPR参数与PTCR陶瓷相变有明显的对应关系,并给出微观结构上的初步解释。研究表明EPR谱线以及精细结构的分析可以为PTCR陶瓷的相变机制以及上的初步解释。研究表明EPR谱线以及精细结构的分析可以为PTCR陶瓷的相变机制以及PTC效应的机制研究提供新的途径。     

Effect of atmosphere on the PTCR properties of BaTiO3 ceramics

The influence of low-temperature annealing, at < 360 °C, in various reducing and oxidizing atmospheres for a series of BaTiO₃ ceramics with a positive temperature coefficient of resistance (PTCR) is discussed. Combined impedance and modulus spectroscopy is used to analyse a.c. impedance data and shows that the total resistance of the sample can be composed of up to three components, dependent on the cooling rate from the sintering temperature. For quickly cooled samples the PTCR response is dominated by an outer shell on individuals grains, whereas for slowly cooled samples the grain boundary resistance dominates. Annealing in reducing atmospheres destroys the grain boundary PTCR effect whereas the outer-shell grain PTCR effect is relatively insensitive to the reducing atmosphere. It is proposed that the acceptor states responsible for the outer-grain and grain-boundary PTCR effects are predominantly intrinsic metal vacancies, i.e. Ba and/or Ti, and adsorbed oxygen, respectively.     

Sintering and properties of highly donor-doped barium titanate ceramics

The electrical properties of donor (La³⁺) doped BaTiO₃ samples with a donor concentration in the range from 0.3 to 1.5 mol.% of La were studied. Samples were sintered at a low partial pressure of oxygen in order to facilitate anomalous grain growth and donor incorporation. In order to optimise the PTCR anomaly, the samples were annealed in air at 1100°C. Results show that with the use of a specific sintering profile PTCR ceramics containing an amount of donor dopant >0.3 mol.%, can be prepared. Heavily doped samples which do not exhibit anomalous grain growth show a core shell structure.     

Influence of sintering conditions on the electrical properties and the PTCR effect of the multilayer Ba1.005(Ti1?xNbx)O3 ceramics with Ni internal electrode

The effects of the Nb-dopant content and the sintering conditions on the electrical properties and the positive temperature coefficient of resistance (PTCR) effect of Ba_1.005(Ti_1?xNb_x)O₃ (BTN) ceramics were investigated, which were sintered at 1,070–1,220?°C for 0.5–6?h in a reducing atmosphere and then re-oxidized at 600–750?°C for 1?h. The results indicated that both the sintering temperature and sintering time affected the electrical properties and the PTCR effect of the multilayer BTN samples, whose room-temperature (RT) resistance first reduced and then increased as a function of the donor–doped concentration at all sintering temperature; moreover, the higher the sintering temperature was, the lower the critical dopant concentration. The BTN ceramics showed a remarkable PTCR effect, with a resistance jump greater by 3.3 orders of magnitude, along with a low RT resistance of 0.3?Ω at a low reoxidated temperature of 600?°C after sintering in a reducing atmosphere.     

蒸汽掺杂-一种新的钛酸钡基PTCR陶瓷的掺杂方法

晶界铲应是陶瓷材料所固的的特性,利用某些氧化物在高温下具有较高的蒸汽压,在烧成过程对陶瓷材料进行掺杂改性,可以有效地控制晶界行为,改善材料性能,钛酸钡基半导体陶瓷中存在的ＰＴＣＲ效应,是一种典型的晶界效应。     

A novel method to regulate the density of BaTiO3 ceramics for positive temperature coefficient resistance via tape casting

BaTiO₃ ceramics for positive temperature coefficient resistance (PTCR) were fabricated via tape casting technique and reduction/reoxidation process. A novel method was used to regulate the density of the ceramics via changing binder amount in tape casting green bodies. The influences of different amounts of the binder on density, electrical properties, and microstructure of ceramics were investigated. The BaTiO₃ ceramic monolith without internal electrodes with an addition of binder of 0.84 wt% was sintered in reducing atmosphere at 1150 °C and reoxidized at 800 °C for 1 h showed a resistivity of 56 Ω·cm and a PTCR jump about 3.2 orders of magnitude. The green and sintered density of the samples decreased with the increasing binder amount. The room temperature resistivity increased monotonically with the binder amount. However, the correlation of the PTCR jump with binder amount showed a contrary tendency. These electrical properties can be explained by the Jonker model. The influences of sintering temperature on the density of BaTiO₃ ceramics with different binder amount were also discussed. In addition to the ceramic monoliths without internal electrodes, multilayer elements with internal electrodes were also prepared.