Group-theoretical study of cationic ordering in perovskite structure
- PDF / 2,485,866 Bytes
- 12 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 202 Views
RY OF CRYSTAL STRUCTURES
GroupTheoretical Study of Cationic Ordering in Perovskite Structure V. M. Talanova, M. V. Talanova, and V. B. Shirokovb, c a
SouthRussian State Technical University, Novocherkassk, 346400 Russia email: [email protected] b Southern Federal University, RostovonDon, 344090 Russia c Southern Scientific Center, Russian Academy of Sciences, RostovonDon, Russia Received July 8, 2013
Abstract—Atomic ordering in the structure of cubic perovskite has been investigated by the grouptheoretical method. The possibility of existence of 13 ordered phases in the 1(a) position (including four binary, two ter nary, and five quaternary cationic superstructures) and 13 phases with different types of ordering in the 1(b) position (including four binary, two ternary, and five quaternary cationic superstructures) is established. Cal culated structures of some types of ordered lowsymmetry perovskite modifications are reported. DOI: 10.1134/S1063774514050186
INTRODUCTION Compounds with perovskite structure, which have been intensively investigated since the 1940s, are applied in various fields of technology and science [1–5]. The characteristics that are most important for appli cations are ferroelectricity, superconductivity, magne tism, and ionic conductivity. It was shown in numer ous studies that atomic ordering in the perovskite structure plays an important role in the formation of structure, achievement of thermodynamic stability of the system, and modification of physical properties [6, 7]. Variations in the degree of far and shortrange orders significantly affect the magnetic state, electronic and ionic conductivities, magnetoresistance, dielectric, ferroelectric, and other physical properties of crystals of this family. It is generally accepted that there may be three types of cation arrangement in the В sublattice of per ovskites: one random and two ordered, with the sodium chloride structure and a layered structure [1, 6–15]. The number of known A2BB'X6 compositions with ordering of B and B' cations in the В sublattice of perovskite, similar to the distribution of cations and anions in the sodium chloride structure, is about 400 [8]. This type of cation ordering (referred to as the NaCltype ordering) is most widespread in the perovs kite family. Only one composition with a layered struc ture of ordered A2BB'X6 phase (La2CuSnO6), stabilized by the additional rotation of octahedra, was indicated in review [8]. Ion ordering is due to the electrostatic forces induced by the difference in the ion charges and the elastic forces related to the difference in their sizes [12]. There is a general regularity of cation ordering in the В sublattice of perovskite: if the dif ference in the formal charges of cations is smaller than
two, one observes the disordered arrangement of cations (examples are BaLaScMoO6, SrLaFeTiO6, CaLaMnTiO6, etc.); if this difference exceeds two, the arrangement is ordered (Sr2NiWO6, Sr2LiReO6, Ba2SrWO6, etc.); and, if the difference in charges is exactly two, there m
Data Loading...
