微波等离子烧结ZnO/Bi2O3系压敏电阻研究

采用常规微波和微波等离子对比烧结ZnO/Bi2O3系压敏电阻发现:两者均可快速成瓷,烧结时间由常规的20 h减少到45 min;烧结后,ZnO晶粒细小(约1μm)均匀,相比而言,等离子更有利于压敏电阻烧结。45 min等离子烧结后,压敏电阻瓷体密度为5.01 g/cm3,ZnO压敏电阻中已有尖晶石相(Zn7Sb2O12)生成,烧结时瓷体收缩均匀,漏电流小,但稳定度差。采用“液相掺杂”可以提高压敏电阻在微波等离子烧结后的电性能稳定度,液相加入比例范围为5%~15%。     

银掺杂量对ZnO压敏电阻电性能的影响

通过传统的固相反应法在920℃制备了银掺杂的ZnO压敏电阻样品,考察了银掺杂量对样品烧结特性和电性能的影响。结果表明,银掺杂不利于样品的致密,但对于ZnO压敏电阻的电性能有明显的影响。当银在ZnO基体中的质量分数由15%增加到25%时,样品的压敏电压由1900V/cm降到600V/cm,对应的非线性系数由15.4降到9.0。这为进一步控制ZnO压敏电阻的电性能提供了新的途径。     

叠烧对ZnO压敏电阻中Bi_2O_3挥发的控制

采用高能球磨法制备ZnO压敏电阻混合粉体。用XRD、SEM对其形貌和微观结构进行了表征。研究了叠烧烧结时,不同位置ZnO压敏电阻中Bi2O3的挥发情况及对其电性能的影响。结果表明:中心位置处ZnO压敏电阻的非线性系数为31,较表层提高100%;其漏电流为6.0μA,电位梯度为345V/mm。Bi2O3的挥发,呈现从中心到表层逐步加剧的趋势。     

（Bi2O3、ZnO）对（Zr0．8Sn0．2）TiO4介电性能的影响

采用常规固相合成工艺研究了添加剂Bi2O3、ZnO等对(Zr0.8Sn0.2)TiO4的烧结性能、微观结构和微波介电性能的影响.结果表明,陶瓷的烧结温度随着Bi2O3含量的增大而降低,而陶瓷的最大烧结密度随着Bi2O3的增大而增大;当w(Bi2O3)>3%时,其烧结可降低至1175℃;各种材料配方均能烧结出致密的陶瓷.陶瓷的介电常数随着Bi2O3含量的增大而略有增大,但增加幅度较小;而材料的介电损耗则随Bi2O3含量的增大而增加,且增大幅度较大.当w(ZnO)=1%、w(Bi2O3)=3%时,可在1190℃获得致密的陶瓷,在测试频率1 MHz下,介电常数约41,介电损耗为1.5×10-4,其综合微波介电性能最佳.     

(Mg_(1–x)Zn_x)TiO_3系陶瓷微波介电性能的研究

以MgCO3、ZnO和TiO2为原料,用固相反应法制备了(Mg1–xZnx)TiO3(MZT)系陶瓷。研究了ZnO含量对其微观结构和微波介电性能的影响。结果表明:添加适量ZnO,可有效降低烧结温度,拓宽烧结温度范围。当x(ZnO)为30%,烧结温度为1250℃时,MZT陶瓷具有优良微波介电性能,εr为16～18,Q·f为90000GHz,τc为–5.1×10–7℃–1。     

LBSCA玻璃对微波介电陶瓷Li_2ZnTi_3O_8性能的影响

Li_2ZnTi_3O_8(LZT)陶瓷具有很好的微波介电性能,但其烧结温度较高(1 150℃),与低温共烧陶瓷(LTCC)工艺不兼容。该文通过掺杂低熔Li2O-B2O3-SiO2-CaO-Al_2O_3(LBSCA)玻璃来降低Li_2ZnTi_3O_8陶瓷的烧结温度,并详细研究了LBSCA掺杂量对材料体系物相结构、微观形貌、致密化程度及微波介电性能的综合影响。研究结果发现,当LBSCA的质量分数为1.5%,并在900℃低温烧结时可表现出优异的微波介电性能,即相对介电常数εr=23,品质因数与频率的乘积Q×f=39 762,密度ρ=3.59g/cm3,频率温度系数τf=-13.75×10-6/℃,能很好地应用于LTCC技术领域。     

微波烧结法制备Bi_2O_3-ZnO-Ta_2O_5陶瓷

研究了三元体系Bi2O3-ZnO-Ta2O5微波陶瓷的微波烧结情况,从烧结机理、陶瓷结构、显微形貌和介电性能等方面对微波烧结的样品和常规烧结样品进行了比较.实验结果表明,微波烧结大幅度缩短了烧结时间,并且很好地促进了Bi2O3-ZnO-Ta2O5陶瓷的致密化,制成的样品晶粒细小均一,且介电性能在一定程度上得到了优化.     

添加CuO对Zn_2SiO_4陶瓷微波介电性能的影响

研究了固相添加CuO对Zn1.8SiO3.8陶瓷的烧结温度、微观结构、相结构及微波介电性能的影响。结果表明,CuO的加入有助于降低Zn1.8SiO3.8陶瓷的烧结温度,Zn1.8SiO3.8陶瓷的烧结温度从1 350℃降到1 000℃。其中掺杂w(CuO)=5%(质量分数)的Zn1.8SiO3.8陶瓷,在1 000℃烧结3h可获得结构致密的烧结体,且微波介电性能达到最佳:介电常数εr=6.5,品质因数与频率之积Q·f=39 373GHz,频率温度系数τf=-48×10-6/℃。     

BaBSi玻璃对ZnVSb基压敏电阻结构与性能的影响

通过传统工艺制备出Ba-B-Si玻璃相掺杂的Zn-V-Sb基压敏电阻材料,研究了其微观结构及性能。结果表明,Ba-B-Si玻璃相的掺杂能降低Zn-V-Sb基压敏电阻试样的烧结温度,玻璃相中B2O3的含量过多,会使ZnO压敏电阻材料的伏安(V-I)特性变差;而Ba2 含量的增加,使ZnO压敏电阻材料的非线性系数上升。     

TiO_2对BLT微波介质陶瓷结构及介电性能的影响

采用传统固相烧结工艺制备了BaO-La2O3-nTiO2(n为3,4,5和6)微波介质陶瓷,研究了该系陶瓷的相组成、微观形貌和微波介电性能之间的关系。结果表明:该系陶瓷具有较优介电性能的主晶相为斜方晶系BaLa2Ti4O12,并且第二相的存在对其介电性能影响明显。烧结体致密性是Q·f及τf的重要影响因素。当n为4时,获得相对较优的介电性能:εr为139.7,Q·f为1239.0GHz和τf达180.0×10–6℃–1。     

Nb_2O_5掺杂量对ZnO压敏电阻器性能的影响

通过掺杂微量Nb2O5制备了ZnO压敏电阻器,运用扫描电子显微镜(SEM)和电性能测试手段分析了Nb2O5掺杂对ZnO压敏电阻器微观结构和电性能的影响,测量了晶界势垒高度φH,并探讨了其对ZnO压敏电阻器性能的影响。结果表明:掺杂适量的Nb2O5可以明显改善ZnO压敏电阻器的微观结构和电性能;当Nb2O5的掺杂量为摩尔分数0.10%时,所制ZnO压敏电阻器的晶粒尺寸最大,且压敏电压V1mA、非线性系数α和φH值分别为174V,30和0.463 eV。     

Mechanism and Development of TiO2-Doped ZnO-Bi2O3-Based Varistors

This paper reviews the history of ZnO varistor, discribes its properties and recent technological status and forecasts its evolution. The future development trend is to produce the low-voltage high-energy multi-layer ZnO varistors. After the two additives are classified by their functions, the effect mechanism of Bi2O3 and TiO2 additives are researched theoretically. TiO2 will make ZnO grain grow bigger and V1mA/mm be depressed down. Especially the colloid TiO2 additive in the scale of nanometer brings about a new method to realize the low voltage of ZnO varistor, which resolves the problem of how to disturb nanometer powder evenly. Moreover the sintering temperature has prominent effect on the electrical properties of ZnO varistors. Generally, the appropriate sintering temperature for low-voltage ZnO varistor ceramics should not be more than 1 250℃. These provide an effective method and rationale for studying low-voltage ZnO varistors.     

Mechanism and Development of TiO_2-Doped ZnO-Bi_2O_3-Based Varistors

This paper reviews the history of ZnO varistor,discribes its properties and recenttechnological status and forecasts its evolution.The future development trend is to produce the low-voltage high-energy multi-layer ZnO varistors.After the two additives are classified by their functions,the effect mechanism of Bi_2O_3 and TiO_2 additives are researched theoretically.TiO_2 will make ZnO graingrow bigger and V_ImA/mm be depressed down.Especially the colloid TiO_2 additive in the scale ofnanometer brings about a new method to realize the low voltage of ZnO varistor,which resolves theproblem of how to disturb nanometer powder evenly.Moreover the sintering temperature has prominenteffect on the electrical properties of ZnO varistors.Generally,the appropriate sintering temperature forlow-voltage ZnO varistor ceramics should not be more than 1 250℃.These provide an effective methodand rationale for studying low-voltage ZnO varistors.     

钨掺杂对二氧化钛压敏电阻瓷电性能的影响

通过对样品的伏案性质、介电常数以及晶界势垒的测量和分析,研究了WO3对TiO2压敏电阻瓷电性能的影响。研究发现掺入x(WO3)为0.25%的样品表现出最好的压敏性质,其压敏电压为42.5V/mm,非线性系数α达到9.6,以及较高的相对介电常数(εr=7.41×104),是一种具有较好潜力的电容-压敏电阻器。通过不同烧结温度的实验,发现1 350℃是最佳烧结温度。类比ZnO压敏材料的晶界势垒模型,提出了适合TiO2压敏材料的肖特基势垒模型。     

ZnO添加对MgTiO3陶瓷的烧结及微波介电性,能的影响

采用传统固相反应法制备了Mg0.95Zn0.05TiO3(MZT)微波介质陶瓷,研究了添加ZnO对MgTiO3陶瓷的烧结过程及介电性能的影响.结果表明,添加ZnO不仅有效降低了MgTiO3陶瓷的烧结温度,提高了陶瓷的致密度,而且有效抑制了中间相MgTi2O5的产生,提高了MgTiO3陶瓷的微波介电性能.当ZnO添加量为...     

Non-ohmic effect and pulse aging behavior of V/Mn/Co/Bi/Dy co-doped ZnO semiconducting varistors with sintering processing

We examined the effect of sintering on the microstructure, non-ohmic properties, clamping characteristics, and pulse aging behavior of V/Mn/Co/Bi/Dy codoped ZnO semiconducting varistors. The average grain size increased from 4.7 to 10.4 µm and the densities of the sintered pellets decreased from 5.47 to 5.37 g/cm³ with the increase in sintering temperature. The maximum non-ohmic coefficient (35.3) was obtained at a sintering temperature of 900 °C. Varistors sintered at 900 °C exhibited the best clamp characteristics, a clamp voltage ratio of 1.74–2.54 at a pulse current of 1–25 A. Varistors sintered at 925 °C exhibited the strongest electrical stability; variation rates for the breakdown field measured at 1.0 mA/cm², for the non-ohmic coefficient, and for the leakage current density were 3.4%, 6.6%, and −11.2%, respectively, after application of a pulse current of 100 A.     

Computational Study on the Microstructural Evolution and the Change of Electrical Resistivity of Sintered Materials

The change of electrical resistivity of materials during sintering has been investigated. The evolution of two-dimensional microstructures during sintering was evaluated using Monte Carlo simulation featuring neck formation, grain growth, and contraction of the powder compacts. The overall electrical resistivity of the sintered microstructure, calculated by Kirchhoff’s first law, was related to the microstructure development during sintering, depending on microstructural parameters such as size and distribution of grains and pores. The solid-state sintering process of monosized particles was divided into three regimes: neck formation, densification, and grain growth. The resistivity dropped significantly at the very initial stage due to neck formation, and decreased slowly as pores were annihilated, while it remained almost unchanged after complete pore removal. For the sintering of randomly packed random-sized particles, the electrical resistivity dropped at the initial stage due to the neck formation, and then continuously decreased by a combined effect of compact densification and grain growth.     

CTLA陶瓷微波介电性能及烧结特性研究

采用固相反应法制备了0.65CaTiO3-0.35LaAlO3(CTLA)陶瓷,研究了CTLA陶瓷的物相组成、烧结特性及微波介电特性。结果表明,CTLA陶瓷只含有Ca0.65La0.35Al0.35Ti0.65O3主晶相,不存在第二相。烧结温度在1 380～1 450℃间,陶瓷的微波介电性能最佳,介电常数εr=44.5,频率温度系数τf≈0,品质因数与频率之积Q×f≈43 948GHz。当w(Nb2O5)=10%时能使陶瓷致密化烧结温度降到1 300℃,但微波性能变差,εr=38.3,τf=-2.8×10-6/℃,Q×f=13 260GHz。     

直流微电机用环形低压压敏电阻器的性能比较

测量了目前直流微电机消噪用 Zn O和 Sr Ti O3两类环形压敏电阻器的特性参数 ,分析了它们的介电 -频率和介电 -温度特性 ,并与所研制的用籽晶法制备的 Zn O压敏电阻的性能相比较。比较测量结果说明 ,采用籽晶法制备的 Zn O压敏电阻器 ,具有易于低压化且压敏特性良好的优点。尽管 Zn O的电容量不及 Sr Ti O3,但由于Zn O压敏电阻的制备属常规工艺且成本低廉 ,在要求价格低的直流微电机应用领域 ,只要提高 Zn O环形压敏电阻器的压敏特性 ,它仍具有较高的实用价值     

B-Zn复合掺杂的LNT微波介质陶瓷的低温烧结

研究了烧结助剂B2O3、ZnO对Li0.925Nb0.375Ti0.8O3(LNT)陶瓷烧结特性及介电性能的影响。结果表明:B2O3-ZnO复合掺杂能有效降低烧结温度至900℃。ZnO的添加调节了LNT陶瓷正的频率温度系数,质量分数为1%的B2O3和4%的ZnO是最佳添加量,可得到εr为59.5,Q·f为7840GHz,τf为0×10–6℃–1的微波介质陶瓷材料。