Growth and Dielectric Properties of Ta-Doped La2Ti2O7 Single Crystals

Abstract

High-quality Ta-doped La 2 Ti 2 O 7 (Ta-LTO) single crystal of about 40 mm in length and 5 mm in diameter was successfully prepared by the optical floating zone method. An X-ray rocking curve reveals that the crystal of LTO has excellent crystalline quality. As-grown crystals were transparent after annealing in air and the transmittance is up to 76% in the visible and near-infrared region. X-ray diffraction showed that this compound possessed a monoclinic structure with P2 1 space group. The dielectric properties were investigated as functions of temperature (0~300 • C) and frequency (10 2 Hz~10 5 Hz). Dielectric spectra indicated an increase in the room-temperature dielectric constant accompanied by a drop in the loss tangent as a result of the Ta doping. One relaxation was observed in the spectra of electric modulus, which was ascribed to be related to the oxygen vacancy. The dielectric relaxation with activation energy of 1.16 eV is found to be the polaron hopping caused by the oxygen vacancies.

Metastable oxygen vacancy ordering state and improved memristive behavior in TiO2 crystals

“…1c [29,30]. The activation energy of 1.03 eV was a typical relaxation value (~1.0 eV) caused by the hopping motion of individual oxygen vacancies [31][32][33]. Regions I and III corresponded to relaxations 1 and 2, respectively, as shown in Fig.…”

Photosensitive Dielectric and Conductivity Relaxation in Lead-Free Cs3Bi2Cl9 Perovskite Single Crystals

“…Electrochemical modulus spectroscopy (MS) as derived from impedance spectroscopy has been widely used to investigate the dielectric behavior and charge-carrier relaxation mechanism in the SC, polycrystalline, and amorphous oxide materials. − Previously, Wang et al investigated the dielectric properties of Ta-doped La 2 Ti 2 O 7 SC over a wide temperature range from 0–300 °C and in the frequency range of 10 2 to 10 5 Hz . Kim et al reported the MS of potassium lithium niobate (KLN) crystals in the frequency range from 100 Hz to 10 MHz and temperature range from 30 to 600 °C and showed that the dielectric relaxation behavior is fitted to the Kohlrausch–Williams–Watts exponential function .…”

“…35−38 Previously, Wang et al investigated the dielectric properties of Ta-doped La 2 Ti 2 O 7 SC over a wide temperature range from 0−300 °C and in the frequency range of 10 2 to 10 5 Hz. 39 Kim et al reported the MS of potassium lithium niobate (KLN) crystals in the frequency range from 100 Hz to 10 MHz and temperature range from 30 to 600 °C and showed that the dielectric relaxation behavior is fitted to the Kohlrausch−Williams−Watts exponential function. 40 Temperature-and frequency-dependent dielectric properties were studied in the KH 2 PO 4 SCs using impedance spectroscopy, and a conduction mechanism was suggested due to protonic hopping between hydrogen vacancies.…”

Preparation of Y-Doped La2Ti2O7 Flexible Self-Supporting Films and Their Application in High-Performance Flexible All-Solid-State Supercapacitor Devices

“…To apply LTO as the main active material to flexible all-solid-state supercapacitors, we can prepare a flexible self-supporting film of LTO, which can also significantly increase the electrochemistry performance and the mechanical property of the flexible device. Moreover, according to the mechanism of oxygen intercalation, the number of oxygen vacancies of LTO can be obviously improved by doping a tertiary component into A or B site of LTO. , As the increase of oxygen vacancies may enhance the capacitance of LTO, we can modify the energy- storage ability of LTO flexible self-supporting films by doping the transition-metal element Y. − In addition, the electrospinning combined with the low-temperature sintering technology is practiced to synthesize these Y-modified self-supporting materials.…”