金属PTC陶瓷复合材料结构及其导电机理

研究了金属ＰＴＣ陶瓷复合材料的电学性能和其材料组分。结果表明，掺入金属的ＰＴＣ陶瓷材料经氮气中烧结，然后在空气中进行热处理，材料表面形成高势垒层，金属ＰＴＣ陶瓷复合材料的室温电阻较ＰＴＣ的陶瓷高。样品之中存在大量不同类型的极化，在低温时样品电阻较高，温度增加后，大量各种类型离子极化出现，在变价金属铁的变价导电作用下，削弱表面势垒，使金属ＰＴＣ陶瓷复合材料电阻降低，表现出ＮＴＣ现象。在电场作用下，正负电荷、晶粒畸变和空位缺陷等产生空间电荷极化使金属ＰＴＣ陶瓷复合材料有较高介电常数。介电损耗（ｔｇδ）频谱和介电δ温度谱上都出现一个介电峰，其主要原因是跃迁极化，金属阳离子由一个位置跃迁到另一个位置，在介电损耗所对应的频率和温度时出现跃迁极化率最大

Structure and Conductive Mechanism of Metal PTC Ceramic Composite

The composition and conductive mechanism of the metal PTC ceramic composite were investigated.It is shown that the PTC ceramic material doped with metal is sintered in the reducing atmosphere N 2, after thermal treatment in air, there are high build in potential layers on the material surface. The room temperature resistance of the metal PTC ceramic composite is higher than that of PTC semiconductor. A great variety of polarizations are there in the metal PTC ceramic composite. At low temperature, the resistance of the metal PTC ceramic composite is higher,and at high temperature, a variety of polarizations to start working,including the charges of Fe chemical valence cause the decrease in surface build in potential,and the samples exhibited NTC phenomenon. The samples have much higher dielectric constants, that is because the space polarizations of the positive and negative charges, crystal lattices and vacance defects. There are maxima in dielectric constant temperature and dielectric loss frequency of the samples, which are caused by the transition of the positive ions. The temperature and frequency maxima corresponding to the dielectric loss peak are consistent with the maxima of positive ion mobility.