Special Issue "Crystals, Films and Nanocomposite Scintillators"

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: closed (30 April 2019).

Special Issue Editors

Guest Editor
Prof. Yuriy Zorenko

Kazimierz Wielki University in Bydgoszcz, Institute of Physics, Bydgoszcz, Poland
Website | E-Mail
Interests: scintillators; development of luminescent materials in the single crystalline and crystals forms; energy transfer proceses in scintillators; defects and dopant as emission and trapping centers in dielectrics
Guest Editor
Prof. Yuriy Malyukin

Institute for Scintillation Materials NAS of Ukraine
Website | E-Mail
Interests: scintillators; deployment of scintillation materials in the micro- and nanopowder forms; energy transfer related phenomena in scintillators

Special Issue Information

Dear Colleagues,

Scintillator materials are known as the spectral and energy transformers of high-energy photons from X- or ɣ-ray ranges into a ultraviolet-visible (UV/VIS) light. The accelerated particles (electrons, protons, neutrons or heavy ions) can also be detected through their energy deposits in scintillator materials, which convert their energy into light. Therefore, the scintillation mechanism can be divided into three consecutive sub-processes: Conversion, transport, and luminescence.

The history of bulk single-crystal scintillators started at the end of the 1940s with the development of NaI:Tl and CsI:Tl. Even today, NaI:Tl and CsI:Tl crystals, as well as CdWO4 and Bi4Ge3O12 oxide crystals, are still the most widely-used scintillators. Meanwhile, over the last twenty years, considerable effort has been observed in the creation of new scintillation materials for high-energy physics and advanced imaging systems for application in industry, science, biology, and medicine. The majority of new single crystal scintillators developed during this period were based on Ce3+ and Pr3+- doped materials, due to their fast scintillation response (up to 100 ns) and high light yield, connected with the 5d-4f radiative transitions of these ions.

Despite the general point of view that the best performance posses single crystal scintillators, not all efficient materials can be grown in the form of bulk crystals with sufficiently large dimensions and prices that are viable for practical applications. The high melting temperatures and the presence of phase transitions between the melting point and room temperature or stoichiometry problems resulting in the formation of different types of point and macro-defects are examples of difficulties that can prevent single crystal preparation. For these reasons the optical ceramics have been used as an alternative to single crystals to provide bulk optical elements in cases where crystals can not be grown, or when transparent or translucent ceramic materials show superior properties in comparison with crystals. The technology of optical ceramics has greatly developed within the last two decades due to the application of these materials as solid state lasers. However, the application demands are a higher quality of ceramic in the case of scintillator, with respect to laser ceramics, because the point defects and structural irregularities can seriously limit a material’s performance due to the introduction of trapping levels in the material band gap.

The development of optical ceramics for scintillator applications is connected to demands for medical imaging. First, fast optical ceramics, based on Ce- and Pr-doped YAG and LuAG, have been reported. In the last decade, R&D in the field of fast-scintillation ceramics has become a hot topic in the search for new scintillation materials. In addition to classical ceramic technologies, new ones, such as spark plasma or combustion sintering, have been developed.

New X-ray-based imaging applications with submicrometer spation resolution have required the development of thin-film scintillators with micrometer scale thicknesses. Liquid phase epitaxy technology is often used for the growth of high-quality single crystalline films onto substrates prepared from well-known optical materials (YAG, YAP, YSO, or saphire). The limitation of performance of film scintillators in this technology is connected to film–substrate misfits and the influence of flux-related impurities on the scintillation properties.

Modern medical therapies, such as photodynamic therapy, strongly demand the development of nanopowder scintillators. Functionalized nanopowder can be directed by blood flow, e.g., to tumor tissues, and, under excitation by X-rays, a single oxygen is produced from the functionalized surface of the grains, which kills the tomor cells. Lanthanide-doped inorganic nanopowders are also considered for future biomedical applications as luminescent nanoprobes.

Nowadays, so-called nanocomposite materials have also become a hot topic in the field of scintillators, with the aim of preparing bulk transparent materials where scintillation characteristics will be defined by a nano-phase dispersed in a suitable host. In principle, these novel materials can include, e.g., organic–inorganic mixtures and offer much higher flexibility in material composition.

In this Special Issue, we aim to introduce and describe, in more detail, the current status in terms of research and development in bulk, ceramic, film, and nanocomposite scintillators, prepared using different technological methods. Both technological descriptions and the various characterization aspects of scintillation materials, together with application aspects in the above metioned fields, will be provided.

Prof. Yuriy Zorenko
Prof. Yuriy Malyukin
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Scintillators
  • crystals, films, ceramics, nanopowders,
  • melt growth, liquid phase epitaxy and solid-state reactions
  • luminescence
  • energy transfer processes
  • defects, dopants

Published Papers (5 papers)

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Research

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Open AccessArticle
Luminescent and Scintillation Properties of CeAlO3 Crystals and Phase-Separated CeAlO3/CeAl11O18 Metamaterials
Crystals 2019, 9(6), 296; https://doi.org/10.3390/cryst9060296
Received: 29 April 2019 / Revised: 29 May 2019 / Accepted: 4 June 2019 / Published: 6 June 2019
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Abstract
This work is dedicated to the growth process and investigation of luminescent and scintillation properties of CeAlO3 single crystals and CeAlO3/CeAl11O18 metamaterials under e-beam and α-particles excitation. It has been shown that cathodoluminescence and radioluminescence spectra of [...] Read more.
This work is dedicated to the growth process and investigation of luminescent and scintillation properties of CeAlO3 single crystals and CeAlO3/CeAl11O18 metamaterials under e-beam and α-particles excitation. It has been shown that cathodoluminescence and radioluminescence spectra of CeAlO3 crystals contain two bands, peaking at 440 and 500 nm, and caused by the Ce3+ 5d–4f transitions into CeAl11O18 phase, which is present in these crystals as an admixture. Under 270 nm ultraviolet (UV) light excitation, a CeAlO3 crystal possesses complicated non-exponential luminescence decay, with the average decay time of 16 ns. The light yield of CeAlO3 crystals under α-particle excitation is about 16% and 12%, in respect to the standard Bi4Ge3O12 (BGO) crystal and Y3Al5O12:Ce (YAG:Ce) single crystalline film samples, respectively. The CeAlO3 scintillation decay is quite fast, with the decay time value t1/e in the 54–56 ns range. Full article
(This article belongs to the Special Issue Crystals, Films and Nanocomposite Scintillators)
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Open AccessArticle
Radio-, Thermo- and Photoluminescence Properties of Lu2O3:Eu and Lu2O3:Tb Nanopowder and Film Scintillators
Crystals 2019, 9(3), 148; https://doi.org/10.3390/cryst9030148
Received: 22 February 2019 / Revised: 7 March 2019 / Accepted: 8 March 2019 / Published: 13 March 2019
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Abstract
This work is dedicated to the preparation and characterization of the radio-, thermo-, and photoluminescent properties of Lu2O3:Eu and Lu2O3:Tb nanopowder (NPs) scintillators, prepared by means of hydrothermal processing, and their film analogues made of [...] Read more.
This work is dedicated to the preparation and characterization of the radio-, thermo-, and photoluminescent properties of Lu2O3:Eu and Lu2O3:Tb nanopowder (NPs) scintillators, prepared by means of hydrothermal processing, and their film analogues made of these NPs by the spin coating method. The luminescent properties of NPs and films were characterized by cathodoluminescence (CL), photoluminescence (PL), X-ray excited radioluminescence (RL), and thermoluminescence (TL) at low and high temperatures. In Lu2O3:Eu NPs and films, mostly the luminescence of Eu3+ ions occupying the C2 site of the host, with the most intensive peaks at 611.6 nm and a decay time of 1.5 ms, was observed. On the contrary, two types of Tb3+ centers in the C2 and C3i sites with the main emission lines at 542.4 and 544.0 nm and the corresponding 4f→5d excitation bands at 270 and 305 nm and decay times of t1/e = 2.17 and 3.96 ms were observed in the case of Lu2O3:Tb NPs and films. Indications were noted that Tb3+ in the C3i symmetry position was most active in the CL spectra of Lu2O3:Tb NPs and a respective film. Thermoluminescent peaks at 110 °C and 170 °C for Lu2O3:Eu NPs and at 75 °C and 120 °C in Lu2O3:Tb NPs were observed corresponding to the hole and electron traps, respectively. Significantly different onsets of temperature quenching of Eu3+ and Tb3+ luminescence in Lu2O3:Eu and Lu2O3:Tb NPs were found at ~90 °C and ~320 °C, respectively. Full article
(This article belongs to the Special Issue Crystals, Films and Nanocomposite Scintillators)
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Open AccessArticle
Different Roles of Ce3+ Optical Centers in Oxyorthosilicate Nanocrystals at X-ray and UV Excitation
Crystals 2019, 9(2), 114; https://doi.org/10.3390/cryst9020114
Received: 17 January 2019 / Revised: 6 February 2019 / Accepted: 19 February 2019 / Published: 21 February 2019
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Abstract
Luminescence properties of Lu2SiO5:Ce3+ and Y2SiO5:Ce3+ nanocrystals were studied using photo- and X-ray luminescence techniques. The crystal structure of Re2SiO5 nanocrystals (P21/c space group) differs from the crystal [...] Read more.
Luminescence properties of Lu2SiO5:Ce3+ and Y2SiO5:Ce3+ nanocrystals were studied using photo- and X-ray luminescence techniques. The crystal structure of Re2SiO5 nanocrystals (P21/c space group) differs from the crystal structure of Re2SiO5 bulk crystals (C2/c space group) with 9- and 7-oxygen-coordinated cation positions instead of 6- and 7-coordinated ones observed for Re2SiO5 bulk crystals. Two optical centers (Ce1 and Ce2) were observed for Re2SiO5:Ce3+ nanocrystals originating from cerium ions substituting 9- and 7-oxygen-coordinated cation sites. Preferential substitution of larger cation sites by cerium ions leads to higher photoluminescence intensity of Ce1 centers, however, Ce2 centers are the main centers for electron-hole recombination, so only Ce2 band is observed in X-ray luminescence spectra. The features of oxygen coordination of Ce1 and Ce2 centers and high content of oxygen vacancies in Re2SiO5:Ce3+ nanocrystals can provide preferential trapping of electrons near Ce2 centers, and therefore, the dominant role of Ce2 band in X-ray luminescence spectra. Full article
(This article belongs to the Special Issue Crystals, Films and Nanocomposite Scintillators)
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Open AccessArticle
Thermoluminescent Properties of Cerium-Doped Lu2SO5 and Y2SiO5 Single Crystalline Films Scintillators Grown from PbO-B2O3 and Bi2O3 Fluxes
Crystals 2018, 8(3), 120; https://doi.org/10.3390/cryst8030120
Received: 8 February 2018 / Revised: 22 February 2018 / Accepted: 22 February 2018 / Published: 4 March 2018
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Abstract
In this work we show the influence of material preparation technology on the thermoluminescent properties of single crystalline films (SCFs) of Ce3+-doped Lu2SiO5 (LSO) and Y2SiO5 (YSO) orthosilicates. LSO:Ce and YSO:Ce SCFs were grown by [...] Read more.
In this work we show the influence of material preparation technology on the thermoluminescent properties of single crystalline films (SCFs) of Ce3+-doped Lu2SiO5 (LSO) and Y2SiO5 (YSO) orthosilicates. LSO:Ce and YSO:Ce SCFs were grown by the liquid phase epitaxy method from two different melt-solutions based on PbO-B2O3 and Bi2O3 fluxes. Absorption, cathodoluminescence, and thermoluminescent properties of LSO:Ce and YSO:Ce SCFs grown from the two previously mentioned types of fluxes were compared, and results of spectrally resolved thermoluminescence measurements and thermoluminescent glow curves of SCFs recorded in different spectral ranges were presented. We have found that the observed differences in thermoluminescent properties of the SCFs under study can be caused by the domination of Ce4+ and Pb2+ emission centers in LSO:Ce and YSO:Ce SCFs grown using PbO-B2O3 flux, and Ce3+ and Bi3+ emission centers in the SCFs grown from Bi2O3 flux. Full article
(This article belongs to the Special Issue Crystals, Films and Nanocomposite Scintillators)
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Review

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Open AccessReview
Magnetron Sputtering for ZnO:Ga Scintillation Film Production and Its Application Research Status in Nuclear Detection
Crystals 2019, 9(5), 263; https://doi.org/10.3390/cryst9050263
Received: 24 April 2019 / Revised: 13 May 2019 / Accepted: 15 May 2019 / Published: 20 May 2019
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Abstract
As a wide band-gap and direct transition semiconductor material, ZnO has good scintillation performance and strong radiation resistance, but it also has a serious self-absorption phenomenon that affects its light output. After being doped with Ga, it can be used for the scintillator [...] Read more.
As a wide band-gap and direct transition semiconductor material, ZnO has good scintillation performance and strong radiation resistance, but it also has a serious self-absorption phenomenon that affects its light output. After being doped with Ga, it can be used for the scintillator of ultra-fast scintillating detectors to detect X-ray, gamma, neutron, and charged particles with extremely fast response and high light output. Firstly, the basic properties, defects, and scintillation mechanism of ZnO crystals are introduced. Thereafter, magnetron sputtering, one of the most attractive production methods for producing ZnO:Ga film, is introduced including the principle of magnetron sputtering and its technical parameters’ influence on the performance of ZnO:Ga. Finally, ZnO:Ga film’s application research status is presented as a scintillation material in the field of radiation detection, and it is concluded that some problems need to be urgently solved for its wider application. Full article
(This article belongs to the Special Issue Crystals, Films and Nanocomposite Scintillators)
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