Zheng Liaoying

Potential Barrier Behavior of BaTiO3—(Bi0.5Na0.5)TiO3 Positive Temperature Coefficient of Resistivity Ceramic*

High-Curie-temperature (Tc) lead-free Y-doped 90 mol%BaTiO3—10 mol%(Bi0.5Na0.5)TiO3 ceramic with positive temperature coefficient of resistivity (PTCR) is prepared by the conventional solid state reaction in nitrogen atmosphere. The PTCR ceramic exhibits a room-temperature resistivity (ρ25) of ~500Ωcm and a high PTCR effect (maximum resistivity (ρmax)/minimum resistivity (ρmin)) of ~4.5 orders of magnitude. A capacitance-voltage approach is first employed to calculate the potential barrier (Φ) of the grain boundary of PTCR ceramic above Tc. It is found that the potential barrier changes from 0.17 to 0.77 eV as the temperature increases from 180 to 220°C, which is very close to the predictions of the Heywang–Jonker model, suggesting that the capacitance-voltage method is valid to estimate the potential barrier of PTCR thermistor ceramics.

高居里温度BaTiO 3 -(Bi 0.5 Na 0.5 )TiO 3 无铅正温度系数电阻陶瓷的制备

用传统的固相反应烧结法制备了(1– x mol%)BaTiO3-xmol%(Bi0.5Na0.5)TiO3(BBNTx)高温无铅正温度系数电阻( positive temperature coefficient of resistivity, PTCR)陶瓷。X射线衍射表明所有的BBNT x 陶瓷形成了单一的四方钙钛矿结构。SEM分析结果显示随着BNT含量的增加, 陶瓷晶粒尺寸减小。空气中烧结的0.2mol% Nb掺杂的BBNT1陶瓷, 室温电阻率为~10 2 Ω·cm, 电阻突跳为~4.5个数量级, 居里温度为~150℃。氮气中烧结的0.3mol% Nb掺杂的BBNTx(10≤x≤60)陶瓷, 同样具有明显的PTCR效应, 居里温度在180~235℃之间。随着BNT含量的增加, 材料的室温电阻率增大, 同时陶瓷的电阻突跳比下降。用传统的固相反应烧结法制备了(1– x mol%)BaTiO3-xmol%(Bi0.5Na0.5)TiO3(BBNTx)高温无铅正温度系数电阻( positive temperature coefficient of resistivity, PTCR)陶瓷。X射线衍射表明所有的BBNT x 陶瓷形成了单一的四方钙钛矿结构。SEM分析结果显示随着BNT含量的增加, 陶瓷晶粒尺寸减小。空气中烧结的0.2mol% Nb掺杂的BBNT1陶瓷, 室温电阻率为~10 2 Ω·cm, 电阻突跳为~4.5个数量级, 居里温度为~150℃。氮气中烧结的0.3mol% Nb掺杂的BBNTx(10≤x≤60)陶瓷, 同样具有明显的PTCR效应, 居里温度在180~235℃之间。随着BNT含量的增加, 材料的室温电阻率增大, 同时陶瓷的电阻突跳比下降。