Incorporation of Er³⁺ into BaTiO₃

Abstract

The incorporation of Er3+ into BaTiO3 ceramics was investigated on samples containing 0.25, 0.5, 1, 2, 8, and 10 at.% of dopant, after sintering at 1350–1550°C in air. For Er3+ concentrations ≤1 at.%, dense and large‐grained ceramics with low room‐temperature resistivity (102–103Ω·cm) were obtained. The observed properties are largely independent of stoichiometry. Simultaneous substitution of Er3+ at both cation sites, with higher preference for the Ba site, is proposed. The behavior of heavily doped ceramics depends on stoichiometry. When Ba/Ti < 1, the electrical properties change from slightly semiconducting to insulating as Er concentration increases from 2 to 8 at.%. The ceramics have tetragonal perovskite structure and contain a large amount of Er2Ti2O7 pyrochlore phase. On the other hand, when Ba/Ti > 1, the ceramics are insulating, fine‐grained, and single phase. In this case, incorporation of Er3+ predominantly occurs at the Ti site, with oxygen vacancy compensation. Incorporation is accompanied by a significant reduction of tetragonality and by expansion of the unit cell. The different results indicate that Er3+ solubility at the Ba site does not exceed 1 at.%, whereas solubility at the Ti site is at least 10 at.%. However, the incorporation of Er3+ and the resulting properties are also strongly affected by sintering conditions.

Dielectric and microstructural properties of BaTiO3 and Ba0.9925Er0.0075TiO3 ceramics

“…The ions with small ionic radii such as La 3+ and Ce 3+ will substitute into A-site whereas the ions with bigger ionic radii such as Lu 3+ and Yb 3+ possibly substitute at B site of BaTiO 3 structure. The ions that have amphoteric behaviour such as Y 3+ , Dy 3+ , Ho 3+ and Er 3+ can occupy both cation lattice site in the BaTiO 3 structure [3][4]. The influence of the dopant incorporation into BaTiO 3 as well as the influence of some transition metal and large rare earth ions in the structural and electrical properties of BaTiO 3 ceramics has been extensively investigated.…”

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

“…% Er 3+ -doped BaTiO 3 7,9 . According to literature 3,7 , both the nominal Ba/Ti molar ratio of R (≡ 0.77) < 1 and the low value of 0.5 at. % Er 3+ considered here should favor the preferential incorporation of Er 3+ at the Ba 2+ sites, leading to the electron compensation mechanism (Kröger and Vink notation):…”

“…Also, the ionic radius (IR) of the substituting element may strongly affect the incorporation site. For instance, ions with intermediate size like Er 3+ (1.00 Å) 6 can be accommodated at both Ba 2+ (1.61 Å) 6 and Ti 4+ (0.605 Å) 6 sites (called amphoteric effect), depending on doping concentration and stoichiometry of the hosting BaTiO 3 structure, according to literature 3,7,8 . The study of defect chemistry of rare-earth cations in BaTiO 3 and, in particular, that of phase development and PTCR response of Er 3+ -doped BaTiO 3 have been achieved elsewhere 3,[7][8][9] .…”

“…For instance, ions with intermediate size like Er 3+ (1.00 Å) 6 can be accommodated at both Ba 2+ (1.61 Å) 6 and Ti 4+ (0.605 Å) 6 sites (called amphoteric effect), depending on doping concentration and stoichiometry of the hosting BaTiO 3 structure, according to literature 3,7,8 . The study of defect chemistry of rare-earth cations in BaTiO 3 and, in particular, that of phase development and PTCR response of Er 3+ -doped BaTiO 3 have been achieved elsewhere 3,[7][8][9] . Considering however that i) there are relatively few works dealing with rare earthinduced semiconductivity in BaTiO 3 in presence of co-doping cations taking effectively part of the bulk structure, and ii) a supposed right combination of host and doping elements may lead to the finding of optimized materials for the applications being envisaged, the purpose of the present work was the study of Er .…”

Dielectric behavior of CaCu3Ti4O12 electro-ceramic doped with La, Mn and Ni synthesized by modified citrate-gel route

“…Partial substitution of appropriate cations in CCTO is considered as an effective method to improve the physical properties of the materials. The radius, valancy and co-ordination number of an element are important parameters to determine the site it occupies  in the parent compound and the composition range of solid solution formation [7]. It is well known that the dielectric properties of CCTO are strongly dependent upon the processing condition as well as doping effects [8,9].…”