The effects of Nd2O3 additives and Al2O3-SiO2-TiO2 sintering aids on the electrical resistivity of (Ba,Sr)TiO3 PTCR ceramics

• Published in: Materials chemistry and physics Vol. 40; no. 3; pp. 168 - 172
• Main Authors: Lai, Chun-Hung, Weng, Chen-Tsang, Tseng, Tseung-Yuen
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.1995
• Subjects: Acceptor-state density; Barriers; Grain boundaries; Permittivity; Positive temperature coefficient of resistance; Grain boundaries; Positive temperature coefficient of resistance; Acceptor-state density; Permittivity; Barriers
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/0254-0584(95)01473-X

The influences of Nd donors and Al2O3-SiO2-TiO2 (AST) sintering aids on the electrical properties of (Ba,Sr)TiO3 materials have been investigated. The room-temperature resistivity and the temperature coefficient of the anomalous resistivity rise were used to characterize the performance of the samples. From derivations based on the Heywang-Jonker barrier model, both characterizing parameters are expected to increase as a result of higher acceptor-state density at the grain boundary. The surface acceptor density, whose value was extracted from the slope in the Arrhenius plot of resistivity versus 1/(Tϵm), where ϵm is the measured permittivity and T the absolute temperature, was found to decrease with the Nd content and increase with the AST dopant. A satisfactory interpretation of the observed variations in resistivity-temperature curves caused by additions of various dopants was thus obtained in the light of the resultant acceptor state density.