Cation size effects-modified phase and PTCR development in Er3+ and Ca2+ co-doped BaTiO3 ceramics during sintering

Abstract

Development of the positive temperature coefficient of resistivity (PTCR) in Er 3+ and Ca 2+ co-doped ferroelectric BaTiO 3 was studied in this work, with Er 3+ being used to act as a donor doping. Irrespective of all the materials showing high densities after sintering at 1200 to 1300 °C, these revealed insulator at the lowest sintering temperature, changing to semiconducting and PTCR-type materials only when the sintering temperature was further increased. Observations from X-ray diffraction help correlating this effect with phase development in this formulated (Ba,Ca,Er)TiO 3 system, considering the formation of initially two separated major (Ba,Ca) TiO 3 -and minor (Ca,Er)TiO 3 -based compounds, as a consequence of cation size-induced stress energy effects. Thus, appearance and enhancement here of the semiconducting and PTCR responses towards higher sintering temperatures particularly involve the incorporation of Er 3+ into the major phase, rendering finally possible the generation and "percolative-like" migration of electrons throughout the whole material.

Self-Powered Bipolar Photodetector Based on a Ce-BaTiO3 PTCR Semiconductor for Logic Gates

“…Based on the above results, it is assumed that the increased Ti 3+ in 0.05%Ce-BTO comes from two sources: first, the removal of oxygen from the lattice allows for more Ti 4+ to be reduced to Ti 3+ ; second, the substitution of Ce 3+ for Ba 2+ gives rise to Ti 3+ due to the necessity of charge compensation . As a result, the increased amount of Ti 3+ contributes to the black color of the 0.05%Ce-BTO ceramic . However, it seems that the black color is not uniform, maybe due to the uneven distribution of Ti 3+ .…”

“…40 As a result, the increased amount of Ti 3+ contributes to the black color of the 0.05%Ce-BTO ceramic. 41 However, it seems that the black color is not uniform, maybe due to the uneven distribution of Ti 3+ . The Ce-doping in BaTiO 3 ceramics leads to the appearance of electrical resistivity change and semiconducting properties.…”

Synthesis and Characterization of (1-x)BaTiO3-xBaF2-xLiF Ceramics

“…More recently Jonker extended this model by considering the influence of the polarization on the resistivity below T C . Several studies were carried out on the appearance of PTCR effect about the doped BaTiO 3 with Ba 2 LaBiO 6 , Y or Er 3+ [11][12][13] but no study is found about a BaTiO 3 -BaF 2 -LiF system. In our case, the appearance of the semi conduction is probably du to an excess of BaF 2 , wich leads at donor levels within this ceramics.…”