A new insight into structural complexity in ferroelectric ceramics

Abstract

Abstract:The structure of the ferroelectrics has been widely studied in order to pursuing the origin of high electromechanical responses. However, some experiments on structure of ferroelectrics have yielded different results. Here, we report that the controversial phase structure is due to the adaptive diffraction of nanodomains which hides the natural crystal structure, and the electric-field-induced phase transition is that the natural crystal structure reappears due to the coalescent nanodomains or ordering nanodomains by applying a high electric field. The temperature dependence of dielectric constant with different measurement frequencies and X-ray diffraction (XRD) patterns of unpoled, poled, and annealing after poled ceramics in Bi 0.5 Na 0.5 TiO 3 -BaTiO 3 (BNT-BT) ceramics authenticate the statement. These results provide a new insight into the origin of structural complexity in ferroelectric ceramics, which is related to the key role of nanodomains.

Low temperature a/b nanotwins in Ni50Mn25+xGa25−x Heusler alloys

“…In general, the nanotwinning is not uncommon and is often reported in ferroelectrics 28 – 33 . Although the ferroelectrics are oxides, we can use the theoretical apparatus and observations related to nanotwinning also for magnetic shape memory alloys.…”

“…The important consequence of nanotwinning is that it generates peak shifts and symmetries in the diffraction pattern, which do not correspond to the true unit cell. It has been clearly illustrated in experiments that some higher symmetry phases are superficial originating from (adaptive) nanotwinning of the original lower symmetry phase 31 – 33 . Previously, Ustinov et al .…”

Unusual crystal structure evolution, multiple phase boundaries and phase coexistence in (1 −x)Ba(Cu1/3Nb2/3)O3-(x)PbTiO3perovskite solid solution

“…Over the years, numerous models have been discussed in the literature to help understand the phenomena of phase coexistence in ferroelectric perovskite solid solutions and how it relates to the physical features of these materials. These models revolve around the concepts of MPB, 52 polymorphic phase boundary, adaptive phases by miniaturization of domains 12,13,53 coherent phase interfaces, 54 phase separation, 35,37 sub-micron level structural heterogeneities, 4,55 positional lattice site heterogeneities, 4,56 composite phase formation, random phase fields, 55 local distortion around Pb-ion in Pb-based materials, 56 spatial compositional variance (concerning both statistical and solubility gaps), etc. 4,7,56 Furthermore, some of the terms coined in the phase coexistence domain concerning the different ionic sizes of the 'B' site cations in perovskite structure are local strain variations, different polar clusters, incomplete diffusion, etc.…”

Structure and electrical properties of [(Na0.825K0.175)0.5Bi0.5]1+xTiO3piezoceramics with A-site nonstoichiometry

“…A great deal of modification work has been conducted since the early 1990s. Other approaches have been proved to be helpful in the poling of the ceramics, as well as, in improving their electrical properties, include the formation of new solid solutions, such as, Bi 0.5 (K x Na 1-x-y Li y ) 0.5 TiO 3 [6], BaTiO 3 (BT)-BNT [3,7], BNT-Na NbO 3 [8], K 0.5 Bi 0.5 TiO 3 (BKT)-BNT [5], BT-BNT-BKT [9], BNT-BaTiO 3 -NaNbO 3 [10], BKT-BNT-SrTiO 3 [11], Bi 0.5 (K 0.20 Na 0.70 Li 0.10 ) 0.5 TiO 3 [12], Bi 0.5 (K x Na 1-x-Ag y ) 0.5 TiO 3 [13], and BNT-BT-(Na 0.5 K 0.5 )NbO 3 [14], and doping with metal oxides, such as, Dy 2 O 3 -doped (Na 0.7 K 0.3 ) 0.5 Bi 0.5 TiO 3 [15], Gd 2 O 3 -doped (Na 0.5 Bi 0.5 ) 0.94 Ba 0.06 TiO 3 [16], Li 2 O-doped0.825BNT-0.175BKT [17], La 2 O 3 -doped0. 92BNT-0.08BT [18].…”