Defects and Aliovalent Doping Engineering in Electroceramics

Abstract

Since the positive influences of defects on the performance of electroceramics were discovered, investigations concerning on defects and aliovalent doping routes have grown rapidly in the fields of inorganic chemistry and condensed matter physics. In this article, we summarized the types of defects in electroceramics as well as characterization tools of defects and highlighted the effects of intrinsic and extrinsic defects on the material performances with the emphasis on dielectric, ferroelectric, and piezoelectric properties. We mainly introduced defect related theoretical simulation and experimental results in several typical incipient ferroelectrics, ferroelectrics, and antiferroelectrics. Hence, the influences of defects on the crystal lattice were summed up, and then the main physical mechanisms were highlighted. Particularly, the performance enhancements of aliovalently doped electroceramics were also evaluated and reviewed. Finally, the outlook and challenges were discussed on the basis of their current developments. This article covers not only an overview of the state-of-the-art advances of defects and aliovalent doping routes in electroceramics but also the future prospects that may open another window to tune the electrical performance of electroceramics via intentionally introducing certain defects.

Multifunctional barium titanate ceramics via chemical modification tuning phase structure

“…D, ε r ‐ T curves showing T R‐O , T O‐T , and T C evolutions and phase diagram (inset) of Pb 2+ ‐doped BT ceramics 56,57 . Type II: E, Evolution of ε r ‐ T curves in typically aliovalent cation doped BT ceramics at A site 22,51,58‐62 . Type I of B‐site substitution: F and G, ε r ‐ T curves showing T R‐O , T O‐T , and T C evolutions in BT ceramics by Zr 4+ , Hf 4+ , or Sn 4+ substitution 21,54,68‐73 .…”

“…H, The corresponding phase diagram. Type II: I, Evolution of ε r ‐ T curves in typically aliovalent cation doped BT ceramics at B site 22,49‐51,74,75 . J, Evolution of T C peak showing frequency‐dependent ε r ‐ T curves for relaxor doped BT ceramics.…”

“…For BT, divalent (2+) and trivalent (3+) ions with large ionic radii as well as monovalent (1+) ions generally incorporate into A site to replace Ba 2+ . Divalent (2+) and trivalent (3+) ions with small ionic radii together with high‐valence (ie, tetravalent [4+], pentavalent [5+], hexavalent [6+]) ions are generally incorporated into B site to replace Ti 4+ 49‐52 . It is worth noting that the “large” and “small” here are in comparison with the ionic radii of Ba 2+ (1.61 Å) and Ti 4+ (0.605 Å) 53 …”

“…However, not much attention is paid to the Pb 2+ ‐doped BT materials on account of the lead toxicity even if a higher T C can be achieved. In addition to isovalent Ca 2+ and Pb 2+ , isovalent Sr 2+ 58‐60 and some aliovalent cations can also be introduced into A site, 22,51,61,62 whereas show negative impact on the ferroelectric phase stability and long‐range ferroelectric orders, leading to the diffusion of ferroelectric‐ferroelectric or/and ferroelectric‐paraelectric phase transitions of BT. Two types of diffused behavior can be observed in the temperature dependence of dielectric constant ( ε r ‐ T ) curves, as shown in Figure 2E.…”

WITHDRAWN: Temperature-Dependent Ferroelectric and Piezoelectric Response of Yb3+ and Tm3+ co-Doped Ba0.95Ca0.05Ti0.90Zr0.10O3 Lead-Free Ceramic

“…Doping the perovskite structure of BCTZ materials with rare earth elements or eutectic mixtures could reduce the internal stress and improve the electrical properties by reducing the number of defects [7,8]. Additionally, BCTZ materials co-doped with rare earth elements have electrical properties similar to those of pristine BaTiO 3 materials, which feature phase transformations from the hexagonal, rhombohedral, or tetragonal phase to the cubic phase with increasing temperature [9,10]. Although BCTZ materials co-doped with rare earth elements have shown excellent electrical properties, up-conversion luminescence, and thermal expansion behaviour [11][12][13], the temperature dependence and mechanism of the piezoelectric response have not been extensively studied, despite its importance for practical use of these materials in electronic components.…”