Incipient ferroelectric to a possible ferroelectric transition in Te4+ doped calcium copper titanate (CaCu3Ti4O12) ceramics at low temperature as evidenced by Raman and dielectric spectroscopy

Abstract

Partial replacement of Ti4+ by Te4+ ions in calcium copper titanate lattice improved its dielectric behaviour mostly due to cubic-to-tetragonal structural transformation and associated distortion in TiO6 octahedra. The relative permittivity values (23–30 x 103) of Te4+ doped ceramics is more than thrice that of un-doped ceramics (8 x 103) at 1 kHz. A decreasing trend in relative permittivity with increasing temperature (50–300 K) is observed for all the samples. Barrett’s formula, as a signature of incipient ferroelectricity, is invoked to rationalize the relative permittivity variation as a function of temperature. A systematic investigation supported by temperature dependent Raman studies reveal a possible ferroelectric transition in Te4+ doped ceramic samples below 120 K. The possible ferroelectric transition is attributed to the interactions between quasi-local vibrations associated with the micro-clusters comprising TiO6 and TeO6 structural units and indirect dipole-dipole interactions of off-center B–cations (Ti4+ and Te4+) in double perovskite lattice.

Exceptional dielectric and varistor properties of Sr, Zn and Sn co-doped calcium copper titanate ceramics

“…The convoluted peaks observed above 460 cm −1 to 500 cm −1 may be due to the mixing of rotation-like and stretching vibrational modes arising from B-O 6 octahedra that are not merely restricted to TiO 6 but also to the other dopants at B-site (SnO 6 ). 36,37 These studies reinforce the dielectric data obtained for the co-doped CCTO ceramics in the present study.…”

Quantum paraelectric state and critical behavior in Sn(Pb)$_2$P$_2$S(Se)$_6$ ferroelectrics

“…Probable ferroelectric transition occurs at T C . 28 According to dielectric data of Pb 2 P 2 S 6 [see Fig. 2(a)] deviation from Barrett's equation starts around 75 K. The obtained parameter values (T 1 ≈ 190 K and T C ≈ −370 K) for Pb 2 P 2 S 6 crystal demonstrate that the material does not undergo a ferroelectric phase transition at any finite temperature.…”

Quantum paraelectricity and induced ferroelectricity by germanium doping of (PbySn1–y)2P2S(Se)6 single crystals

“…Therefore, the material does not undergo a ferroelectric phase transition at any finite temperature because of the quantum effects. When θ CW is finite and θ CW < T 1 , the quantum fluctuations that occur below T 1 break the long-range ferroelectric order and stabilize the quantum paraelectric state in the sample, and a probable ferroelectric transition occurs at θ CW [20]. The dielectric data of Pb 2 P 2 S 6 , (Pb 0.98 Ge 0.02 ) 2 P 2 S 6 , (Pb 0.7 Sn 0.3 ) 2 P 2 S 6 + 5% Ge and (Pb 0.7 Sn 0.3 ) 2 P 2 Se 6 + 5% Ge single crystals were analysed on the basis of Barrett's formula (1).…”