SrTiO3—Glimpses of an Inexhaustible Source of Novel Solid State Phenomena

Abstract

The purpose of this selective review is primarily to demonstrate the large versatility of the insulating quantum paraelectric perovskite SrTiO3 explained in “Introduction” part, and “Routes of SrTiO3 toward ferroelectricity and other collective states” part. Apart from ferroelectricity under various boundary conditions, it exhibits regular electronic and superconductivity via doping or external fields and is capable of displaying diverse coupled states. “Magnetoelectric multiglass (Sr,Mn)TiO3” part, deals with mesoscopic physics of the solid solution SrTiO3:Mn2+. It is at the origin of both polar and spin cluster glass forming and is altogether a novel multiferroic system. Independent transitions at different glass temperatures, power law dynamic criticality, divergent third-order susceptibilities, and higher order magneto-electric interactions are convincing fingerprints.

Polar Phonon Behaviour in Polycrystalline Bi-Doped Strontium Titanate Thin Films

“…Perovskite-structured SrTiO 3 (ST) stands out as an incipient ferroelectric with dielectric permittivity increasing continuously on cooling due to the polar-mode softening but without a ferroelectric phase transition [ 1 , 2 , 3 , 4 , 5 ]. Incipient ferroelectrics exhibit small values of the dissipation factor, tanδ, and strong dependence of the real part of the dielectric permittivity, ε′, on electric field, which makes them attractive for applications in tunable electronic components [ 6 , 7 ].…”

“…Among ST-based compounds [ 5 ], Bi-doped ST solid solutions have been intensively studied as for dielectric [ 21 , 22 ] as for resistance-switching memory [ 23 ] and thermoelectric applications [ 24 ]. In Sr 1−1.5x Bi x TiO 3 , ceramics displacements of Bi 3+ ions on cuboctahedral Sr sites were reported to generate local dipole moments that induce dielectric relaxations but harden the ST polar soft mode [ 25 , 26 , 27 ].…”

Dielectric Relaxation, Local Structure and Lattice Dynamics in Mn-Doped Potassium Tantalate Ceramics

“…In both ST- and CT-based systems, Mn 2+ species are strongly off-centred in the oversized cuboctahedral cages, generating electric dipoles. The presence of such positional disorder for Mn 2+ has been invoked as an explanation for the dielectric relaxation and multi-glass (i.e., dipolar plus spin glass) behaviour observed in Mn-doped ST [ 7 ]. The multi-glass state has been associated with polar displacements of Mn 2+ in the highly polarizable incipient ferroelectric lattice, thereby initiating a transition of the Mn 2+ magnetic moments into a spin glass.…”

“…Mn-doped KT ceramics [ 17 , 18 , 19 ] feature a relaxation at low frequencies, while in the microwave range, the relaxational effects are manifested in tanδ, but not in ε′ [ 19 , 20 , 21 ]. The K 0.97 Mn 0.03 TaO 3±δ ceramics [ 17 , 18 ] display both dielectric and magnetic anomalies, which resemble the “multi-glass” behaviour observed in Mn-doped ST [ 7 , 22 ]. However, the interpretation of the magnetic response in K 0.97 Mn 0.03 TaO 3±δ is complicated because of a contribution from the second phase, MnO y .…”

Sequential Synthesis Methodology Yielding Well-Defined Porous 75%SrTiO3/25%NiFe2O4 Nanocomposite

“…The system SrTiO 3 /NiFe 2 O 4 is known mostly for its capability as a visible-light-driven photocatalyst [ 7 , 8 ]. SrTiO 3 (STO) is a prototypical cubic perovskite oxide with unique physical properties, such as wide bandgap, high dielectric constant, thermal stability, and large permittivity [ 9 , 10 , 11 ]. Besides, SrTiO 3 is known as versatile powder support for the formation of heterostructures with specific properties for technological applications [ 12 , 13 , 14 , 15 , 16 ], because SrTiO 3 , as an intrinsic paraelectric, is able to stabilize ferroelectric order via substrate-induced strain, cation doping, 18 O isotope substitutions, and defect engineering [ 17 ].…”