Positive temperature coefficient of resistance effect in Na2Ti6O13-doped 0.94BaTiO3–0.06(Bi0.5Na0.5)TiO3 ceramics

Abstract

The positive temperature coefficient of resistance (PTCR) characteristics of Na2Ti6O13 (NT)-doped 0.94BaTiO3–0.06(Bi0.5Na0.5)TiO3 (BBNT) ceramics were investigated in order to evaluate the effect of NT as a new additive for lead-free PTCR thermistor application. The BBNT ceramic sintered at 1325°C exhibited a relatively high Curie temperature (TC) of 158°C while its PTCR characteristic was not satisfactory for thermistor application. However, doping with NT significantly influenced the PTCR behavior of BBNT ceramic. It is considered that NT was responsible for grain growth of the BBNT by forming a liquid phase during sintering due to its low melting temperature of 1300°C. The grain growth resulted in the enhanced PTCR characteristics of BBNT ceramic. In particular, 0.1 mol% NT doped BBNT ceramic exhibited excellent PTCR performance of low resistivity at room temperature (1.6×102 Ω cm), resistivity increase near TC (1.28×104) and high TC of 158°C, suitable for lead-free PTCR thermistor application.