【摘要】 本文研究了GeO₂-K₂CO₃和MoO₃掺杂的(Na_0.3K_0.7)NbO₃铁电半导体陶瓷的PTC效应。导出了存在粒间相情况下铁电体表面势垒表示式,这是对Heywang模型的一种修正,利用修正的Heywang模型对（Na,K）NbO₃半导体陶瓷的PTC效应进行了解释。更多还原

【Abstract】 The dielectric properties and PTC effect in (Na0.3K6. 7)NbO3 semiconducting ceramics are studied. Two dielectric constant anomalies on ε(T) curve at 430℃ and 220℃ have been observed. The temperature hysteresis is found for slow heating and cooling rates for all the specimens. By additions of GeO2-K2CO3 glasses and MoO3 as the donor, two anomalies of resistivity are observed at 430℃ and about 200℃ in this ferroelectric semiconductor. The change in the resistivity at room temperature caused by the amount of added MoO3 is investigated.By taking account of the intergranular layers of the glassy phase, an expression for surface potential barriers, a modified Heywang model, is derived. The conduction mechanism in (Na, K)NbO3 semiconducting ceramics is discussed and the modified Heywang model is used to explain the PTC effect in (Na0.3K0.7)NbO3 semiconducting ceramics.更多还原