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Title: Features of the structural states of KNbO{sub 3} single crystals before and after fast-neutron irradiation

Abstract

Neutron irradiation is a unique tool for forming new structural states of ferroelectrics, which cannot be obtained by conventional methods. The inf luence of the irradiation by two doses of fast neutrons (F = 1 × 10{sup 17} and 3 × 10{sup 17} cm{sup –2}) on the structure and properties of KNbO{sub 3} single crystals has been considered for the first time. The developed method for taking into account the experimental correction to the diffuse scattering has been used to analyze the structural changes occurring in KNbO{sub 3} samples at T = 295 K and their correlations with the behavior of dielectric and nonlinear optical characteristics. The irradiation to the aforementioned doses retains the KNbO{sub 3} polar structure, shifting Т{sub Ð}¡ to lower temperatures and significantly affecting only the thermal parameters and microstructure of single crystals. Neutron irradiation with small atomic displacements provides a structure similar to the high-temperature modification of an unirradiated KNbO{sub 3} crystal.

Authors:
; ; ; ; ; ; ;  [1]
  1. State Scientific Center of the Russian Federation Karpov Institute of Physical Chemistry (Russian Federation)
Publication Date:
OSTI Identifier:
22645266
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 62; Journal Issue: 1; Other Information: Copyright (c) 2017 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMIC DISPLACEMENTS; DIFFUSE SCATTERING; FAST NEUTRONS; FERROELECTRIC MATERIALS; MICROSTRUCTURE; MONOCRYSTALS; NIOBATES; NONLINEAR PROBLEMS

Citation Formats

Stash, A. I., E-mail: astas@yandex.ru, Ivanov, S. A., Stefanovich, S. Yu., Mosunov, A. V., Boyko, V. M., Ermakov, V. S., Korulin, A. V., and Kalyukanov, A. I.. Features of the structural states of KNbO{sub 3} single crystals before and after fast-neutron irradiation. United States: N. p., 2017. Web. doi:10.1134/S1063774517010230.
Stash, A. I., E-mail: astas@yandex.ru, Ivanov, S. A., Stefanovich, S. Yu., Mosunov, A. V., Boyko, V. M., Ermakov, V. S., Korulin, A. V., & Kalyukanov, A. I.. Features of the structural states of KNbO{sub 3} single crystals before and after fast-neutron irradiation. United States. doi:10.1134/S1063774517010230.
Stash, A. I., E-mail: astas@yandex.ru, Ivanov, S. A., Stefanovich, S. Yu., Mosunov, A. V., Boyko, V. M., Ermakov, V. S., Korulin, A. V., and Kalyukanov, A. I.. Sun . "Features of the structural states of KNbO{sub 3} single crystals before and after fast-neutron irradiation". United States. doi:10.1134/S1063774517010230.
@article{osti_22645266,
title = {Features of the structural states of KNbO{sub 3} single crystals before and after fast-neutron irradiation},
author = {Stash, A. I., E-mail: astas@yandex.ru and Ivanov, S. A. and Stefanovich, S. Yu. and Mosunov, A. V. and Boyko, V. M. and Ermakov, V. S. and Korulin, A. V. and Kalyukanov, A. I.},
abstractNote = {Neutron irradiation is a unique tool for forming new structural states of ferroelectrics, which cannot be obtained by conventional methods. The inf luence of the irradiation by two doses of fast neutrons (F = 1 × 10{sup 17} and 3 × 10{sup 17} cm{sup –2}) on the structure and properties of KNbO{sub 3} single crystals has been considered for the first time. The developed method for taking into account the experimental correction to the diffuse scattering has been used to analyze the structural changes occurring in KNbO{sub 3} samples at T = 295 K and their correlations with the behavior of dielectric and nonlinear optical characteristics. The irradiation to the aforementioned doses retains the KNbO{sub 3} polar structure, shifting Т{sub Ð}¡ to lower temperatures and significantly affecting only the thermal parameters and microstructure of single crystals. Neutron irradiation with small atomic displacements provides a structure similar to the high-temperature modification of an unirradiated KNbO{sub 3} crystal.},
doi = {10.1134/S1063774517010230},
journal = {Crystallography Reports},
number = 1,
volume = 62,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2017},
month = {Sun Jan 15 00:00:00 EST 2017}
}
  • The neutron irradiation of ferroelectrics is efficiently used to form structural states that cannot be obtained by conventional technologies. To date, the effect of neutron irradiation on the structure and properties of BaTiO{sub 3} has been studied for only ceramic materials. We have considered the influence of fast-neutron irradiation (F = 1 × 10{sup 17} cm{sup −2}) on the structure and properties of BaTiO{sub 3} single crystals for the first time. The structural changes occurring in irradiated BaTiO{sub 3} and their correlation with the behavior of dielectric and nonlinear optical characteristics are analyzed with the aid of a specially developedmore » method for taking into account the experimental correction to diffuse scattering. Neutron irradiation to the aforementioned dose retains the polar structure of the material and only slightly changes atomic displacements. The radiationinduced structural changes occur according to the high-temperature type to form a structure similar to the cubic modification of unirradiated BaTiO{sub 3} crystal.« less
  • Flux-pinning effects were studied by sequentially irradiating a YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] single crystal to fast neutron fluences of 8[times]10[sup 21] m[sup [minus]2]. From superconducting quantum interference device magnetometry, the transition temperature [ital T][sub [ital c]] and the magnetic moments were obtained for fields parallel and perpendicular to the crystallographic [ital c] axis. Irreversibility lines and critical current densities were evaluated as a function of neutron fluence. In order to explain the data, a qualitative model is developed that is based on the layered structure of the system and the nature of the various defects introduced by irradiation. Because ofmore » the dominating influence of large defect cascades on flux pinning, different summation models have to be employed, depending on temperature, field orientation, field strength, and pin density.« less
  • The density, molar volume, optical energy bandgap, and infrared absorption spectra in the range 400-4000 nm of borate glasses with composition 2xLi{sub 2}O-xAl{sub 2}O{sub 3}-(1-3x)B{sub 2}O{sub 3} (x varying from 0.10 to 0.18 mol fraction) prepared by conventional melt quench technique have been measured before and after successive {gamma}-ray irradiation at the dose of 2.5 K Gy to elucidate the effect of gamma irradiation on such glasses. The radiation induced defects created by {gamma}-ray and the changes in optical properties have been discussed.
  • The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well-known materials, when their structural symmetry is deviated from equilibrium through a small local strain or field. Here, the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO 3 is reported. This phase is found to coexist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network ofmore » ferroelectric domain walls. While the local microstructural shear strain involved is only ≈0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature. Moreover, the meandering walls of the low-symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m -1. In conclusion, this discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals.« less
  • KNbO{sub 3} single crystals are often utilized for their piezoelectric and optical properties. In this study the domain configurations in as-grown single crystals were investigated using reflected light microscopy, scanning electron microscopy and atomic force microscopy. Using atomic force microscopy it was possible to image the distortion induced on the crystal surface by the domain walls and to quantify the predicted angle between (001){sub pc} planes across these walls for the cases of both 90 deg. domain walls and S walls. These features can also be imaged using the other two techniques. This direct measurement of surface distortion verifies themore » geometrical model of domain structures, and suggests that any possible strain energy considerations are minor in predicting the surface topography in the material after phase changes from the growth temperature.« less