Crystallographic shear in niobium oxides of different compositions

Two phase diagrams of Pb(Ti0.485Zr0.515)0.98(Nb0.5Bi0.5)0.02O3 solid solution in the temperature range 20 ≤ t ≤ 600°C

“…The reasons for the former anomaly were described in detail in [5]; it was shown therein that the volume is constant due to two competing processes: temperature expansion and structure compacting in the crystallographic shear planes (CSPs). The latter are the main planar defects in the real structure of Pb(Ti x Zr 1 -x )O 3 (PZT) solid solutions [6] and other solid solutions having a ABO 3 perovskite structure and containing ions with variable valence (such as Ti [7] or Nb [8]) in B sites. The latter anomaly will be explained below.…”

Effect of nonstoichiometry on the structure and dielectric properties of bismuth ferrite

“…As was established for AgNbO 3 and NaNbO in [2][3][4], the formation of impurities in ceramics fabricated via solid state synthesis is due to a deficiency of А posi tions in the ABO 3 structure (structural nonstoichiom etry), which occurs upon a crystallographic shift (CS), i.e., a plane defect characteristic of oxygen octahedral compounds of the ReO 3 type that contain elements with variable valency in the В position [5,6]. After a CS, the stiochiometric mixture of initial components contains excess А cations, which, depending on their properties, are either localized in intergrain spacers or partially displace В cations from their positions with the formation of impurity compounds.…”

Phase equilibria and electrical properties of barium-containing relaxor-based solid solutions

“…In the range 0.025 < x ≤ 0.05, V meas increases slightly, but the increase is inconsistent with the V theor (x) data, and c/a also increases. This behavior of the unit cell lvolume and distortion with increasing x can be accounted for as follows: In АВО 3 perovskite oxides containing variable valence ions, rearrangement of the oxygen octahedra in crystallo graphic shear planes [21][22][23][24] Table 2 presents γ values obtained previ ously [18,25,26]. It is seen that the γ values for Ti containing oxides are on the same order of magnitude as the composition range where the unit cell volume is constant in this system.…”

“…If it has an M structure, the number of domain configura tions is 30 (6T + 24M). In some sense, this composi tional phase transition can be treated by analogy with CaTiO 3 0.027 [24,25] SrTiO 3 0.027 [24,25] BaTiO 3 0.022 [24,25] CdTiO 3 0.021 [24,25] PbTiO 3 0.025 [24,25] the ferroelectric-paraelectric phase transition that occurs in ferroelectrics as the temperature is raised. The phase transition is accompanied by structural instabilities, which leads to a sharp increase in piezo electric responses.…”