钛酸钡基NTC热敏陶瓷电阻的制备与研究
摘要
钛酸钡基陶瓷材料在居里点Tc之前呈现良好的NTC特性,关于BaTiO3陶瓷在NTC特性及其机理方面的研究,迄今国内外很少见报导,是一个比较新的研究方向。钛酸钡基NTC功能陶瓷有着广阔的市场应用前景和重要的研究价值。根据氧化物半导体理论获得高电阻率、低B值材料是困难的。为满足物联网、汽车电子、各种半导体器等对宽温区温度补偿和测温应用急剧增长的需要,因此要求NTC热敏材料实现高电阻值、低B值。而采用常规的热敏材料配方是无法实现的。高电阻值、低B值热敏材料己成为当今负温度系数热敏电阻制造的一大难题。
本实验采用固相合成法合成BaTiO3基NTC热敏陶瓷电阻材料,通过添加Pb以提高材料的居里点,以扩大NTC元件的工作温度范围,研究探索其NTC温度范围内其实现高电阻值、低B值特征的可能性；掺杂Nb205以提高半导化程度,降低材料的电阻率；添加BN做助烧剂,降低烧结温度。
本文主要研究了烧结工艺与配方对BaTiO3基NTC热敏陶瓷材料的影响,并就线性NTC及高电阻率低B值的NTC材料做了研究。主要结论如下：
(1)烧结温度对NTC材料的性能有很大影响,室温电阻率ρ25与烧结温度呈U型关系,本实验中,烧结温度在1180℃时,样品性能较好,为样品的较佳烧结温度。烧结中对样品进行适当的保温有利于助于晶粒半导化,降低室温电阻值,本实验中,保温1h时室温电阻率较小,样品的NTC性能也较好；
(2)Pb能有效提高材料的居里点,扩大材料的工作温度范围。本实验中,居里点T。最高达330℃。同时,Pb的掺杂可以降低材料的电阻率,提高半导化程度；
(3)BN是一种非常有效的助烧剂,能有效降低烧结温度,BN越多烧结温度越低。少量BN和Nb205的加入能提高材料的半导化程度,降低材料的电阻率,实验中BN为2mo1%时室温电阻率较低,ρ25=35.7Ω·cm。同时证实了Nb205有抑制晶粒生长的作用；
(4)实验所得样品,电阻率为1316.7Ω·cm,B值为954.1,属于典型的高电阻率、低B值的NTC热敏电阻,且Tc为330℃,工作温度范围较大,具有良好的应用前景。
At temperature below the Curie point, the BaTiO3-based ceramics presents g ood character of NTC (Negative Temperature Coefficient). The NTC character of BaTiO3-based ceramics is rare studied and reported. High room temperature re sistivity (ρ25) and low B constant thermistors have a broad market application perspective, widely used for temperature measurement and compensation, inrush current limiting, etc. But according to the semi-conduction theory, it is hard t o synthesis using the traditional methods.
The aim of this work is to synthesis and study highρ25 and low B consta nt BaTiO3-based NTC ceramic thermistors. Solid-phase synthesis is used, addin g Pb to shift the Curie point, doping ND2O5 to semi-conduct materials and low erρ25, and doping BN to reduce sintering temperature. The influence of proces s and formulas is studied on the BaTiO3-based NTC materials. Main conclusio ns follow as:
(1) Sintering temperature has a major effect on the materials. The relations hip ofρ25 and sintering temperature is U-shape. Samples show better NTC cha racter at sintering temperature 1180℃. Appropriate time of heat preservation te mperature helps materials semi-conducting. During this experimentρ25 is minim um when the time of heat preservation is 1h
(2) Pb doping is effective for shifting the Curie point. When Pb=60mol%, the Curie point is 330℃which is a lot increment compare to the pure BaTi O3 materials.
(3) BN can reduce the sintering temperature, also help semi-conduction. W hen BN=2mol%, samples'=35.7Ω·cm. Nb2O5 promotes semi-conduction and 1o werρ25. Also it can inhibit grain growth.
(4)ρ25 of synthesized samples is above 1.3k and constant B is below 1k. It is typical highρ25 and low B NTC thermistor. The Curie point is 330℃, s howing good application perspective.
本实验采用固相合成法合成BaTiO3基NTC热敏陶瓷电阻材料,通过添加Pb以提高材料的居里点,以扩大NTC元件的工作温度范围,研究探索其NTC温度范围内其实现高电阻值、低B值特征的可能性；掺杂Nb205以提高半导化程度,降低材料的电阻率；添加BN做助烧剂,降低烧结温度。
本文主要研究了烧结工艺与配方对BaTiO3基NTC热敏陶瓷材料的影响,并就线性NTC及高电阻率低B值的NTC材料做了研究。主要结论如下：
(1)烧结温度对NTC材料的性能有很大影响,室温电阻率ρ25与烧结温度呈U型关系,本实验中,烧结温度在1180℃时,样品性能较好,为样品的较佳烧结温度。烧结中对样品进行适当的保温有利于助于晶粒半导化,降低室温电阻值,本实验中,保温1h时室温电阻率较小,样品的NTC性能也较好；
(2)Pb能有效提高材料的居里点,扩大材料的工作温度范围。本实验中,居里点T。最高达330℃。同时,Pb的掺杂可以降低材料的电阻率,提高半导化程度；
(3)BN是一种非常有效的助烧剂,能有效降低烧结温度,BN越多烧结温度越低。少量BN和Nb205的加入能提高材料的半导化程度,降低材料的电阻率,实验中BN为2mo1%时室温电阻率较低,ρ25=35.7Ω·cm。同时证实了Nb205有抑制晶粒生长的作用；
(4)实验所得样品,电阻率为1316.7Ω·cm,B值为954.1,属于典型的高电阻率、低B值的NTC热敏电阻,且Tc为330℃,工作温度范围较大,具有良好的应用前景。
At temperature below the Curie point, the BaTiO3-based ceramics presents g ood character of NTC (Negative Temperature Coefficient). The NTC character of BaTiO3-based ceramics is rare studied and reported. High room temperature re sistivity (ρ25) and low B constant thermistors have a broad market application perspective, widely used for temperature measurement and compensation, inrush current limiting, etc. But according to the semi-conduction theory, it is hard t o synthesis using the traditional methods.
The aim of this work is to synthesis and study highρ25 and low B consta nt BaTiO3-based NTC ceramic thermistors. Solid-phase synthesis is used, addin g Pb to shift the Curie point, doping ND2O5 to semi-conduct materials and low erρ25, and doping BN to reduce sintering temperature. The influence of proces s and formulas is studied on the BaTiO3-based NTC materials. Main conclusio ns follow as:
(1) Sintering temperature has a major effect on the materials. The relations hip ofρ25 and sintering temperature is U-shape. Samples show better NTC cha racter at sintering temperature 1180℃. Appropriate time of heat preservation te mperature helps materials semi-conducting. During this experimentρ25 is minim um when the time of heat preservation is 1h
(2) Pb doping is effective for shifting the Curie point. When Pb=60mol%, the Curie point is 330℃which is a lot increment compare to the pure BaTi O3 materials.
(3) BN can reduce the sintering temperature, also help semi-conduction. W hen BN=2mol%, samples'=35.7Ω·cm. Nb2O5 promotes semi-conduction and 1o werρ25. Also it can inhibit grain growth.
(4)ρ25 of synthesized samples is above 1.3k and constant B is below 1k. It is typical highρ25 and low B NTC thermistor. The Curie point is 330℃, s howing good application perspective.
引文
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[15]关振铎,张中太,焦金生.无机材料物理性能[M].北京:清华大学出版社,2004.
[16]郭炜,李玲霞等.掺杂Nb2O5及MgO对细晶BaTiO3系统介电性能影响的研究[J].硅酸盐通报,2003,22(1)：22-25.
[17]王悦辉,庄志强Nb、Co、La掺杂对BaTiO3介质陶瓷性能的影响[J].电子元件与材料,2005,24(1)：29-31.
[18]郭文华,李钢.Nb2O5掺杂对BaTiO3陶瓷介电常数的影响[J].中国陶瓷,2006,42(10)：24-26.
[19]E.Brzozowski,M.S.Castro.Grain growth control in Nb-doped BaTi03[J].Journal of Materials Processing Technology,2005,168(3):464-470.
[20]郭建高,赵青,常爱民,吉光.超宽温区负温度系数热敏电阻材料的开发[J].仪表技术与传感器,2009(B11)：110-111.
[21]汪宝宁.NTC技术在微动同步器标度因数的温度补偿中的应用[J].上海航天,1997,14(4)：32-35.
[22]周惠明.高精度负温度系数热敏电阻及其应用[J].国外电子元器件,1995(2)：23-26.
[23]陈后胜,曹湘君.抑制浪涌电流用NTCR热敏电阻器的失效模型[J].电子元件与材料,2001,21(2)：14-15.
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