Resistivity Anomaly in Doped Barium Titanate

Abstract

The barrier-layer model previously proposed to explain the anomalous increase in resistivity that occurs in doped BaTiOs has been reexamined in the light of data obtained from more recent experiments. The picture thus obtained describes correctly and quantitatively the resistivity anomaly and the frequency and voltage dependence of t h e resistivity in the entire temperature range investigated (-180" to +200°C). The activation energy of the donors and of t h e surface states as well as the density of states in BaTi03 were determined and are in close agreement with other investigations. Comments are made regarding t h e uncertainty of the nature of the surface states.

The Effect of Isovalent Substitutions and Dopants of 3d-Metals on the Properties of Ferroelectrics- Semiconductors

“…17-50 • C (see figure 2, range I) and ca. 300-500 • C (see figure 2, range III) is described by the equations [1,12]:…”

“…The variation of the resistance in the temperature range ca. 100-300 • C, where a PTCR effect manifests itself, is usually described in terms of the Heywang model [1]:…”

“…Positive temperature coefficient of resistance (PTCR) occurs in ferroelectric semiconducting ceramics based on doped barium titanate near Curie point due to the formation of potential barriers at grain boundaries [1]. Therefore, PTCR ceramics are synthesized in the conditions at which semiconducting grains and highresistance grain boundaries are formed.…”

Preparation of BaPbO3 functional ceramics from leaded waste

“…Because of the perovskite structure of BaPbO 3 [14,15], the PTC characteristic of BaPbO 3 could be speculated by the Heywang model [16]. The electrons from oxygen vacancies could act as charge carriers.…”

Barrier capacitance of nonstoichiometric barium titanate

“…Controlled valency semiconductors sintered in air (24,28,36) show a large increase in resistivity at the Curie point and extending to higher temperatures. This anomoly is known in the titanates as the positive temperature coefficient (PTC) effect.…”