The behavior of high temperature quantum paraelectricity in some perovskite titanates

Systematic study of photoluminescence upon band gap excitation in perovskite-type titanates R1/2Na1/2TiO3:Pr (R=La, Gd, Lu, and Y)

“…The selected inter-atomic distances and angles of RNTO (R ¼ La, Gd, Lu, and Y) were summarized in Table 1. The same as previous reports [24][25][26][27][28], the lattice parameters, R, Na-O distances, and Ti-O-Ti bond angles decrease; i.e., tilt angles increase, with increasing the ionic radius of R ion in RNTO (R ¼ La, Gd, Lu, and Y). On the other hand, the Ti-O distances are similar despite of a decrease in the lattice parameters, resulting in the almost same BVSs of Ti (see Table 1).…”

“…Shan et al [24][25][26][27][28] reported that R 1/2 Na 1/2 TiO 3 (R ¼ La, Pr, Nd, Gd, Eu, Tb, Yb, Y) have perovskite-type structure and the lattice parameter decreased and the tilting angle of TiO 6 octahedra increases with a decrease in the ionic radius [29] of R ion. The change in lattice parameter and tilt angle of TiO 6 octahedron brings in the change in chemical bond between Ti and O, i.e., the change in width of valence and conduction bands which primarily consist of Ti 3d and O 2p orbitals [30].…”

Magnetic and ferroelectric orders in strained Gd1/2Na1/2TiO3: First-principles calculations

“…Moreover, all LnNTO compounds have the Pnma structure. 4,5 The dielectric response is substantially dependent on the Ln ionic size and thus the lattice distortion, including the rotation and tilting of Ti octahedra. It was revealed that the dielectric plateau at T!0 falls and the values of both T a and T s increase with the atomic number from La to Yb or with the distortion magnitude of Ti-octahedra.…”

“…So far, the structural distortion and dielectric/optical responses of LnNTO compounds have been preliminarily investigated and the role of the 4f electrons has been rarely addressed. 4,6,[12][13][14][15][16] Here, two prominent issues should be mentioned. First, the Ln species mostly show big 4f moments.…”