Influence of lattice polarizability on interacting Li-induced dipoles distributed in incipient ferroelectricKTaO3

Abstract

Susceptibility purely originated from the Li-induced quasistatic dipoles in relaxor K 1−x Li x TaO 3 has been extracted from low-frequency permittivity using terahertz time-domain spectroscopy. The temperature dependence of the extracted susceptibility has an anomaly at the critical temperature T a near 100 K with the critical slowing down of the low-frequency relaxation process. From a detailed analysis of the extracted susceptibility, we attributed the main part of the susceptibility for x Յ 0.036 to the high-frequency relaxation process and concluded that there are two relevant interactions that govern the ferroelectric coupling between Li-induced dipoles and that the interplay of the two interactions gives rise to a complex temperature dependence of the susceptibility originated from Li-induced dipoles. Below the critical concentration x Ͻ 0.022, short-range interaction between individual Li ions should be dominant. Above the critical concentration, x Ͼ 0.022, Coulomb interaction should be dominant. The crossover from the low-temperature glasslike phase to the lowtemperature ferroelectric domain-state across x c in K 1−x Li x TaO 3 is attributed to the interplay of the two kinds of interaction.

Evidence of polar nanoregions in quantum paraelectric KTaO3

“…Among these nominally pure crystals, one finds so called quantum paraelectric or incipient ferroelectric such as potassium tantalate KTaO 3 , or strontium titanate SrTiO 3 , which possess polar soft mode, but do not exhibit ferroelectric phase transition and remain in the paraelectric cubic phase down to 0.003 K [2][3][4]. The transverse optic TO 1 soft mode is stabilized by zero-point quantum fluctuations [5]. KTaO 3 and SrTiO 3 crystals possess highly polarizable lattice.…”

Growth of Incipient Ferroelectric KTaO3 Single Crystals by a Modified Self-Flux Solution Method

“…Undoped and doped KT single crystals have been synthesized by different techniques including Czochralski method, growth from melt, top-seed solution method and flux one. − In the latter case KT single crystals were obtained by self-flux solution process, using K 2 CO 3 as the flux. ,− The crystals were obtained by heating up the starting reagents (potassium carbonate and tantalum oxide) to 1450 °C and held at this temperature for 1−2 h. The average size of the as-grown crystals varied from tens of millimeters to almost one centimeter. , However, the high synthesis temperature used increased markedly the difficulty in controlling KT stoichiometry.…”

Electric field‐revealed precursor ferroelectric properties of low lithium ion‐doped KTaO3

“…The incipient ferroelectric (or so‐called quantum paraelectric) potassium tantalate crystal, KTaO 3 (KT for short), remains in its centrosymmetric cubic phase down to the lowest temperatures and does not undergo any ferroelectric phase transition . KT has the polar soft TO 1 transverse optic mode that is stabilized by the zero‐point quantum fluctuations of atoms and thus prevents the softening of TO 1 . KT crystal has a highly polarizable lattice, and is very sensitive to even small amounts of defects, impurities, and application of electric and elastic field .…”