Dielectric Properties of SrTi 18 O 3

Itoh, Makoto; Wang, Ruiping; Narahara, Miho; Kyômen, Tôru

doi:10.1080/00150190390205825

Cited by 7 publications

(3 citation statements)

References 28 publications

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“…An activation of TO phonon modes below T C has been observed with Raman spectroscopy [70]. In SrTi( 16 O 1−y 18 O y ) 3 (STO18) ferroelectricity appears above an 18 O substitution level of around 35%, evidenced by the appearance of a peak in the dielectric constant [43,67] and a hardening of the TO 1 soft-mode seen in Raman measurements below T C [71]. Figure 1d compares T C measured in both CaSTO and STO18.…”

Section: Multiple Roads Towards Ferroelectricitymentioning

confidence: 74%

Metallicity and Superconductivity in Doped Strontium Titanate

Collignon

Lin

Rischau

et al. 2019

Annu. Rev. Condens. Matter Phys.

116

127

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Strontium titanate is a wide-gap semiconductor avoiding a ferroelectric instability thanks to quantum fluctuations. This proximity leads to strong screening of static Coulomb interaction and paves the way for the emergence of a very dilute metal with extremely mobile carriers at liquid-helium temperature. Upon warming, mobility decreases by several orders of magnitude. Yet, metallicity persists above room temperature even when the apparent mean free path falls below the electron wavelength. The superconducting instability survives at exceptionally low concentrations and beyond the boundaries of MigdalEliashberg approximation. An intimate connection between dilute superconductivity and aborted ferroelectricity is widely suspected. In this review, we give a brief account of ongoing research on bulk strontium titanate as an insulator, a metal, and a superconductor. CONTENTS

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Section: Multiple Roads Towards Ferroelectricitymentioning

confidence: 74%

Metallicity and Superconductivity in Doped Strontium Titanate

Collignon

Lin

Rischau

et al. 2019

Annu. Rev. Condens. Matter Phys.

116

127

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“…Their properties are very sensitive to even small amounts of impurities, defects, electric and elastic applied fields. Itoh et al [28,29] induced ferroelectricity in a SrTiO 3 crystal below T C D 23K, by an isotope substitution of 18 O for 16 O. In this way, quantum fluctuations disappear and a long-range ferroelectric order is possible.…”

Section: Introductionmentioning

confidence: 95%

Coexistence of the relaxor-like and ferroelectric behavior in K_1-xLi_xTaO₃

et al. 2016

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The results of low-temperature linear and nonlinear susceptibilities, polarization measurements and the dc electric field dependence of the dielectric properties of the lithium-doped potassium tantalate K 1-x Li x TaO 3 , x D 0.034 (KLT-3.4%Li) solid solution are presented. The coexistence of the relaxor-like and ferroelectric behavior and different mechanisms leading to either of them are discussed. The observed ferroelectric phase transition is of the first-order type with temperature hysteresis. This transition is due to the off-center motions of Ta ions in the octahedral environment of oxygen ions. Clusters of Li C ions produce a relaxor-like behavior and random electric field. This field reduces the depolarization field and allows off-center motions of Ta ions and an appearance of spontaneous polarization.

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“…Electrical measurements have been carried out on 18 O substituted STO samples [21] [49]. The measurements have shown them to be ferroelectric, by peaks in the electrical permittivity, and by D vs E hysteresis loops when the substitution factor is high enough.…”

Section: Case Study 2: 18 O Substituted Stomentioning

confidence: 99%

Raman Investigations of Strained Ferroelectrics

Eerd¹

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<p>This describes research done on a variety of ferroelectric systems over the course of three years during the Ph.D. programme at Victoria University of Wellington. The majority of the work involved using Raman spectroscopy to investigate the lattice dynamics of the ferroelectric materials studied, and by this method measuring the structural phase diagrams in the ferroelectrics. Three material systems were investigated. The first was bulk ceramics of the solid solution of Na₀.₅Bi₀.₅TiO₃ and BaTiO₃ (BNT-BT). The second material was PbTiO₃ (PT) nanowires prepared by annealing `PX' phase lead titanate in air. In these samples we found a tensile strain caused by nanoscopic voids in the wires. The third material studied was thin films of SrTiO₃ (STO) grown epitaxially on lattice mismatch substrates. This introduced strain into the system. In the BNT-BT system, temperature dependent Raman spectra were taken of the various samples. From the spectra, it was discovered that the structural phase transitions of the material did not perfectly correspond to the electrical phase transitions. For one significant phase boundary, no structural change occurs, only a loss of long-range order. The local sensitivity of the Raman spectroscopy technique allowed this to be found. As a consequence of this, no tricritical point is found in the phase diagram of BNT-BT. It was also found that poling the sample in electrical fields shifted the morphotropic phase boundary between 5% and 6% Ba-substitution about 1% towards the high-substitution side, but otherwise did not affect the phase diagram. In the PT nanowires system, temperature dependent Raman spectroscopy and scanning electron microscopy were performed to measure the spectra of single nanowires. A large enhancement of the ferroelectric phase transition temperature was discovered. The enhancement was found to be dependent on the nanowire diameter, with peak enhancements of over 100K measured in wires close to 125 nm. Wires both larger and smaller than this showed smaller degrees of enhancement. It is proposed that the enhancement is caused by tensile strain developed in the wires during their synthesis, where they were transformed from a low-density phase into a high-density phase. In the STO thin films system, temperature dependent ultraviolet Raman spectra and x-ray diffraction spectra were measured to establish a relationship between the biaxial strain developed in the films and their phase diagrams. The XRD found strain in the films of similar substrate which was inversely proportional to thickness up to a threshold point. Beyond that point, there is a discontinuity and additional thickness of film is grown without strain. The strain in the lower layer remains constant. The UV Raman spectroscopy method was able to enhance the signal such that thin films with weak signals could be measured. The spectra showed signs of a phase transition in all of the films. In one film enough of the spectral features were visible to characterise the low temperature phase as the orthorhombic ferroelectric phase of STO. The transition temperature varied from sample to sample, and a relationship between the biaxial strain and the transition temperature was seen.</p>

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Dielectric Properties of SrTi 18 O 3

Cited by 7 publications

References 28 publications

Metallicity and Superconductivity in Doped Strontium Titanate

Metallicity and Superconductivity in Doped Strontium Titanate

Coexistence of the relaxor-like and ferroelectric behavior in K_1-xLi_xTaO₃

Raman Investigations of Strained Ferroelectrics

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Dielectric Properties of SrTi 18 O 3

Cited by 7 publications

References 28 publications

Metallicity and Superconductivity in Doped Strontium Titanate

Metallicity and Superconductivity in Doped Strontium Titanate

Coexistence of the relaxor-like and ferroelectric behavior in K1-xLixTaO3

Raman Investigations of Strained Ferroelectrics

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Product

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About

Coexistence of the relaxor-like and ferroelectric behavior in K_1-xLi_xTaO₃