Publications

2017

• Ag nanoparticles in soda-lime glass grown by continuous wave laser irradiation as an efficient SERS platform for pesticides detection
  
  • Tite Teddy
  • Ollier Nadege
  • Sow Mohamed Chérif
  • Vocanson Francis
  • Goutaland François
  Sensors and Actuators B: Chemical, Elsevier, 2017, 242, pp.127 - 131. (10.1016/j.snb.2016.11.006)
  DOI : 10.1016/j.snb.2016.11.006
• The effect of electron and UV irradiation on graphene single layer Raman spectra behaviour
  
  • Shchedrina I.
  • Corbel C.
  • Cavani O.
  • Renault J.-P
  , 2017. The reactivity and homogeneity of graphene surface, and, therefore its Raman spectra, are expected to be dependent on the quantity and type of structural defects that, as reported in literature, can be induced by various treatments, including irradiation . Indeed, for UV irradiation, the evolution of the Raman spectra reveals a strong dependency on the irradiation conditions (light wavelength, electron energy, flux, irradiation dose). Similar behavior was found by other authors using different irradiation conditions. The present work is focused on surface properties changes, induced by irradiation in graphene materials and investigated by Raman and photoluminescence (PL) spectra at the micro scale. The aim is to investigate more specifically the evolution of the Raman and PL spectra before and after different types of irradiation and their correlation. Irradiation tests are performed in dry conditions for graphene single layer deposited on Ni substrate and, to compare, for highly oriented pyrolytic graphite (HOPG). As illustrated on Fig.1 for a graphene monolayer on Ni after 1h UV irradiation, the spectra evolve as the oncentration of electron irradiation induced defects compared to the native defects increase, moreover the Raman and the PL spectra vary independently as the UV flux used for the 1h irradiation increases.
• Discrimination of Polynucleotide Transport through a Highly Hydrophobic Uncharged Nanopore
  
  • Picaud Fabien
  • Paris Guillaume
  • Gharbi Tijani
  • Lepoitevin Mathilde
  • Coulon Pierre-Eugène
  • Bechelany Mikhael
  • Janot Jean Marc
  • Balme Sébastien
  Journal of Physical Chemistry C, American Chemical Society, 2017, 121 (13), pp.7525 - 7532. (10.1021/acs.jpcc.7b00560)
  DOI : 10.1021/acs.jpcc.7b00560
• Spin-torque Effects in Thermally Assisted Magnetization Reversal: Kramers' Escape Rate Theory Approach
  
  • Kalmykov Yuri
  • Byrne Declan
  • Coffey William
  • Dowling William
  • Titov Sergey
  • Wegrowe Jean Eric
  , 2017. Thermal fluctuations of nanomagnets driven by spin-polarized currents are treated via the Landau-Lifshitz-Gilbert equation generalized to include both the random thermal noise field and the Slonczewski spin-transfer torque (STT) term. The reversal time of the magnetization in such a nanomagnet are evaluated for wide ranges of damping by using the method of Coffey et al. [Phys. Rev. E 63, 021102 (2001)]. Their method generalizes the Mel'nikov-Meshkov approach [J. Chem. Phys. 85, 1018 (1986)] for bridging the very low damping (VLD) and intermediate damping (ID) Kramers escape rates for mechanical Brownian particles (the Kramers turnover problem) to the analogous magnetic turnover problem.
• Ab initio study of electron energy loss spectra of bulk bismuth up to 100 eV
  
  • Timrov Iurii
  • Markov Maxime
  • Gorni Tommaso
  • Raynaud Michèle
  • Motornyi Oleksandr
  • Gebauer Ralph
  • Baroni Stefano
  • Vast Nathalie
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2017, 95 (9). The dynamical charge-density response of bulk bismuth has been studied within time-dependent density functional perturbation theory, explicitly accounting for spin-orbit coupling. The use of the Liouville-Lanczos approach allows us to calculate electron energy loss spectra for excitation energies as large as 100 eV. Effects of 5d semicore electronic states, spin-orbit coupling, exchange and correlation, local fields, and anisotropy are thoroughly investigated. The account of the 5d states in the calculation turns out to be crucial to correctly describe the loss spectra above 10 eV and, in particular, the position and shape of the bulk-plasmon peak at 14.0 eV at vanishing transferred momentum. Our calculations reveal the presence of interband transitions at 16.3 eV, which had never been discussed before. The origin of the peak at 5.8 eV is revisited as due to mixed interband and collective excitations. Finally, our study supplements the lack of experiments at finite transferred momenta. (10.1103/physrevb.95.094301)
  DOI : 10.1103/physrevb.95.094301
• Raman and PAS Characterization of Electron Irradiated UO2 to Determine U Displacement Threshold
  
  • Barthe M.F.
  • Desgranges Lionel
  • Mohun Ritesh
  • Desgardin Pierre
  • Simon Patrick
  • Duval Florian
  • Canizarès Aurélien
  • Jegou Christophe
  • Miro Sandrine
  • Cavani Olivier
  • Boizot Bruno
  , 2017.
• Direct observation of the band structure in bulk hexagonal boron nitride
  
  • Henck Hugo
  • Pierucci Debora
  • Fugallo Giorgia
  • Avila Jose
  • Cassabois Guillaume
  • Dappe Yannick J.
  • Silly Mathieu G.
  • Chen Chaoyu
  • Gil Bernard
  • Gatti Matteo
  • Sottile Francesco
  • Sirotti Fausto
  • Asensio Maria C.
  • Ouerghi Abdelkarim
  Physical Review B, American Physical Society, 2017, 95 (8), pp.085410. A promising route towards nanodevice applications relies on the association of graphene and transition metal dichalcogenides with hexagonal boron nitride (h-BN). Due to its insulating nature, h-BN has emerged as a natural substrate and gate dielectric for graphene-based electronic devices. However, some fundamental properties of bulk h-BN remain obscure. For example, the band structure and the position of the Fermi level have not been experimentally resolved. Here, we report a direct observation of parabolic dispersions of h-BN crystals using high-resolution angle-resolved photoemission spectroscopy (ARPES). We find that h-BN exfoliation on epitaxial graphene enables overcoming the technical difficulties of using ARPES with insulating materials. We show trigonal warping of the intensity maps at constant energy. The valence-band maxima are located around the K points, 2.5 eV below the Fermi level, thus confirming the residual p-type character of typical h-BN. (10.1103/PhysRevB.95.085410)
  DOI : 10.1103/PhysRevB.95.085410
• A solution of the paradox of the double-slit experiment
  
  • Coddens Gerrit
  , 2017. We argue that the double-slit experiment can be understood much better by considering it as an experiment whereby one uses electrons to study the set-up rather than an experiment whereby we use a set-up to study the behaviour of electrons. We also show how the concept of undecidability can be used in an intuitive way to make sense of the double-slit experiment and the quantum rules for calculating coherent and incoherent probabilities. We meet here a situation where the electrons always behave in a fully deterministic way (following Einstein's conception of reality), while the detailed design of the set-up may render the question about the way they move through the set-up experimentally undecidable (which follows more Bohr's conception of reality). We show that the expression $\psi_{1} + \psi_{2}$ for the wave function of the double-slit experiment is numerically correct, but logically flawed. It has to be replaced in the interference region by the logically correct expression $\psi'_{1} + \psi'_{2}$, which has the same numerical value as $\psi_{1} + \psi_{2}$, such that $\psi'_{1} + \psi'_{2} = \psi_{1} + \psi_{2}$, but with $\psi'_{1} = {\psi_{1} +\psi_{2}\over{\sqrt{2}}} \,e^{\imath {\pi\over{4}} } \neq \psi_{1}$ and $\psi'_{2} = {\psi_{1} +\psi_{2}\over{\sqrt{2}}}\,e^{-\imath {\pi\over{4}}}\neq \psi_{2}$. Here $\psi'_{1}$ and $\psi'_{2}$ are the correct contributions from the slits to the total wave function $\psi'_{1} + \psi'_{2}$. We have then $p = |\psi'_{1} + \psi'_{2}|^{2} = |\psi'_{1}|^{2} + |\psi'_{2}|^{2} = p_{1}+p_{2} $ such that the paradox that quantum mechanics (QM) would not follow the traditional rules of probability calculus disappears. The paradox is rooted in the wrong intuition that $\psi_{1}$ and $\psi_{2}$ would be the true physical contributions to $\psi'_{1} + \psi'_{2} =\psi_{1} + \psi_{2}$ like in the case of waves in a water tank. The solution proposed here is not ${ad {hoc}}$ but based on an extensive analysis of the geometrical meaning of spinors within group representation theory and its application to QM. Working further on the argument one can even show that an interference pattern is the only way to satisfy simultaneously two conditions: The condition obeying binary logic (in the spirit of Einstein) that the electron has only two mutually exclusive options to get to the detector (viz. going through slit S$_{1}$ or going through slit S$_{2}$) and the condition obeying ternary logic (in the spirit of Bohr) that the question which one of these two options the electron has taken is experimentally undecidable.
• Spin–Charge Conversion Phenomena in Germanium
  
  • Oyarzún Simón
  • Rortais Fabien
  • Rojas-Sanchez Juan-Carlos
  • Bottegoni Federico
  • Laczkowski Piotr
  • Vergnaud Céline
  • Pouget Stéphanie
  • Okuno Hanako
  • Vila Laurent
  • Attané Jean-Philippe
  • Beigne Cyrille
  • Marty Alain
  • Gambarelli Serge
  • Ducruet Clarisse
  • Widiez Julie
  • George Jean-Marie
  • Jaffrès Henri
  • Jamet Matthieu
  Journal of the Physical Society of Japan, Physical Society of Japan 日本物理学会, 2017, 86 (1). (10.7566/JPSJ.86.011002)
  DOI : 10.7566/JPSJ.86.011002
• Ultrafast evolution and transient phases of a prototype out-of-equilibrium Mott-Hubbard material
  
  • Lantz G.
  • Mansart B.
  • Grieger D.
  • Boschetto Davide
  • Nilforoushan, N.
  • Papalazarou E.
  • Moisan, N.
  • Perfetti L
  • Jacques V. L.R.
  • Le Bolloc'H D.
  • Laulhé C.
  • Ravy S.
  • Rueff J.-P.
  • Glover, T. E.
  • Hertlein, M.P.
  • Hussain, Z.
  • Song, S.
  • Chollet M
  • Fabrizio, M.
  • Marsi, M.
  Nature Communications, Nature Publishing Group, 2017, 8, pp.13917. The study of photoexcited strongly correlated materials is attracting growing interest since their rich phase diagram often translates into an equally rich out-of-equilibrium behaviour. With femtosecond optical pulses, electronic and lattice degrees of freedom can be transiently decoupled, giving the opportunity of stabilizing new states inaccessible by quasi-adiabatic pathways. Here we show that the prototype Mott-Hubbard material V$_2$O$_3$ presents a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds. For both the insulating and the metallic phase, the formation of the transient configuration is triggered by the excitation of electrons into the bonding a$_{1g}$ orbital, and is then stabilized by a lattice distortion characterized by a hardening of the A$_{1g}$ coherent phonon, in stark contrast with the softening observed upon heating. Our results show the importance of selective electron-lattice interplay for the ultrafast control of material parameters, and are relevant for the optical manipulation of strongly correlated systems. (10.1038/ncomms13917)
  DOI : 10.1038/ncomms13917
• Ionic Liquids: evidence of the viscosity scale-dependence
  
  • Berrod Quentin
  • Ferdeghini Filippo
  • Zanotti Jean-Marc
  • Judeinstein Patrick
  • Lairez Didier
  • Sakai Victoria Garcia
  • Czakkel Orsolya
  • Fouquet Peter
  • Constantin Doru
  Scientific Reports, Nature Publishing Group, 2017, 7 (1), pp.8 p.. Ionic Liquids (ILs) are a specific class of molecular electrolytes characterized by the total absence of co-solvent. Due to their remarkable chemical and electrochemical stability, they are prime candidates for the development of safe and sustainable energy storage systems. The competition between electrostatic and van der Waals interactions leads to a property original for pure liquids: they self-organize in fluctuating nanometric aggregates. So far, this transient structuration has escaped to direct clear-cut experimental assessment. Here, we focus on a imidazolium based IL and use particle-probe rheology to (i) catch this phenomenon and (ii) highlight an unexpected consequence: the self-diffusion coefficient of the cation shows a one order of magnitude difference depending whether it is inferred at the nanometric or at the microscopic scale. As this quantity partly drives the ionic conductivity, such a peculiar property represents a strong limiting factor to the performances of ILs-based batteries (10.1038/s41598-017-02396-7)
  DOI : 10.1038/s41598-017-02396-7
• Electron and electron-ion sequential irradiation of borosilicate glasses: Impact of the pre-existing defects
  
  • Mir Anamul H.
  • Monnet I.
  • Boizot B.
  • Jégou C.
  • Peuget S.
  Journal of Nuclear Materials, Elsevier, 2017, 489, pp.91 - 98. (10.1016/j.jnucmat.2017.03.047)
  DOI : 10.1016/j.jnucmat.2017.03.047
• Optimal light harvesting in 2D semiconductor heterostructures
  
  • Chen Zhesheng
  • Biscaras Johan
  • Shukla Abhay
  2D Materials, IOP Publishing, 2017, 4, pp.025115. Optoelectronics with two dimensional (2D) heterostructures combining transition metal dichalcogenides (TMDCs) and other semiconductors in hybrid stacks is potentially promising because of the possibility of fabricating devices with high efficiency and new properties. Ultrafast charge transfer across the interface and long lifetime of carriers makes the vertical geometry attractive with respect to traditional bulk heterostructures. In such ultrathin structures, the multiple boundaries and the thickness of each material play a key role in the interaction of light with the device and can strongly influence the device performance. In this article we study light harvesting in 2D InSe/MoS2 semiconductor heterostructures by measuring Raman enhancement or attenuation as a function of layer thicknesses. Measurements are precisely reproduced by the calculation of the light emission, and the field distribution inside the heterostructure. Optimizing layer thickness and material interfaces has a significant effect on the light distribution in such 2D heterostructures with layer thickness in the region of a few tens of nanometers, providing a means to enhance the performance of emerging 2D semiconductor-heterostructure optoelectronics. (10.1088/2053-1583/aa736f)
  DOI : 10.1088/2053-1583/aa736f
• The genesis of the Schaeffler diagram in the history of stainless steel
  
  • Guiraldenq Pierre
  • Hardouin Duparc Olivier
  Metallurgical Research & Technology, EDP Sciences, 2017, 114 (6), pp.613. The Schaeffler diagram is regarded through a historical perspective in order to review Anton Schaeffler's life (1919–2001) and to analyze the genesis of the famous structural abacus that made him known throughout the world and still serves as a reference today. The equivalence coefficients of addition elements complementary to chromium and nickel, either alpha formers or gamma formers, were at the heart of the subject. The crystallographic structures of many standard steels, and hence several of their mechanical properties, can be partly predicted before manufacturing on the sole basis of their chemical compositions. A chronological review helps to understand the creative work that was done during this initial research. (10.1051/metal/2017059)
  DOI : 10.1051/metal/2017059
• Aluminosilicate glasses structure under electron irradiation: An EPR study
  
  • Gac A. Le
  • Boizot B.
  • Jégou C.
  • Peuget S.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2017, 407, pp.203 - 209. (10.1016/j.nimb.2017.06.025)
  DOI : 10.1016/j.nimb.2017.06.025
• Reducing the screening during transmission using non-linear properties of high sensitivity superconductor radiofrequency coils for magnetic resonance micro imaging
  
  • Geahel Michel
  • Rochefort Ludovic De
  • Ginefri Jean-Christophe
  • Darrasse Luc
  • Beek Cornelis Jacominus van Der
  • Briatico Javier
  • Poirier-Quinot Marie
  , 2017, pp.2704. In MRI, high-temperature superconducting (HTS) radio frequency (RF) coils have been shown to greatly improve the signal-to-noise ratio. The nonlinear behavior of superconducting materials as a function of the emitted RF power is, nowadays, one of the principal technological obstacle limiting the use of these materials on a wider scale. It could be overcome by using HTS coil in reception mode only. Here we characterize these non-linear properties and use them to decouple the HTS coil during transmit mode. This preliminary study is a promising approach to use the highly sensitive HTS coils in reception mode only.
• Excitons in van der Waals materials: From monolayer to bulk hexagonal boron nitride
  
  • Koskelo Jaakko
  • Fugallo Giorgia
  • Hakala Mikko
  • Gatti Matteo
  • Sottile Francesco
  • Cudazzo Pierluigi
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2017, 95 (3). We present a general picture of the exciton properties of layered materials in terms of the excitations of their single-layer building blocks. To this end, we derive a model excitonic Hamiltonian by drawing an analogy with molecular crystals, which are other prototypical van der Waals materials. We employ this simplified model to analyze in detail the excitation spectrum of hexagonal boron nitride (hBN) that we have obtained from the ab initio solution of the many-body Bethe-Salpeter equation as a function of momentum. In this way, we identify the character of the lowest-energy excitons in hBN, discuss the effects of the interlayer hopping and the electron-hole exchange interaction on the exciton dispersion, and illustrate the relation between exciton and plasmon excitations in layered materials. (10.1103/PhysRevB.95.035125)
  DOI : 10.1103/PhysRevB.95.035125
• Determination of paramagnetic concentrations inside a diamagnetic matrix using solid-state NMR
  
  • Maron Sébastien
  • Ollier Nadège
  • Gacoin Thierry
  • Dantelle Géraldine
  Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2017, 19 (19), pp.12175-12184. The determination of very low doping levels in solid materials is an important issue for many applications. When considering paramagnetic dopants, NMR relaxation technique appears to be much more accurate than classical techniques such as the Vegard's law resulting from X-ray diffraction (XRD) measurement or chemical analysis that cannot provide information of appropriate dopant spatial distribution. In a recent report, the linear variation of 1/T1, i.e. the nuclear relaxation rate, as a function of Nd3+ content has been used to determine doping levels with a good dispersion homogeneity in the monazite LaPO4 matrix down to 0.1 mol. %. We here extend this study to more complex compounds doped with Nd3+ , such as YPO4, the solid solution Y0.8Sc0.2PO4, Ba5(PO4)3Cl and a phosphate glass. For all considered compounds except Ba5(PO4)3Cl:Nd, 1/T1 is found to be linearly proportional to the nominal Nd concentration, confirming the ability of the method to investigate dopant concentration and spatial homogeneity. The results on different compounds open the discussion on the parameters influencing the nuclear relaxation rate, among which the orbital overlap and the average P-P distances. (10.1039/c7cp00451f)
  DOI : 10.1039/c7cp00451f
• Impacts of composition and beta irradiation on phase separation in multiphase amorphous calcium borosilicates
  
  • Patel Karishma B.
  • Boizot Bruno
  • Facq Sébastien P.
  • Peuget Sylvain
  • Schuller Sophie
  • Farnan Ian
  Journal of Non-Crystalline Solids, Elsevier, 2017, 473, pp.1–16. Borosilicate glasses for nuclear waste applications are limited in waste loading by the precipitation of watersoluble molybdates. In order to increase storage efficiency, new compositions are sought out that trap molybdenum in a water-durable CaMoO4 crystalline phase. Factors affecting CaMoO$_4$ combination and glass-inglass phase separation in calcium borosilicate systems as a function of changing [MoO$_3$] and [B$_2$O$_3$] are examined in this study in order to understand how competition for charge balancers affects phase separation. It further examines the influence of radiation damage on structural modifications using 0.77 to 1.34 GGy of 2.5 MeV electron radiation that replicates inelastic collisions predicted to occur over long-term storage. The resulting microstructure of separated phases and the defect structure were analyzed using electron microscopy, XRD, Raman and EPR spectroscopy prior to and post irradiation. Synthesized calcium borosilicates are observed to form an unusual heterogeneous microstructure composed of three embedded amorphous phases with a solubility limit ~2.5 mol% MoO$_3$. Increasing [B$_2$O$_3$] increased the areas of immiscibility and order of (MoO$_4$)$^{2−}$anions, while increasing [MoO$_3$] increased both the phase separation and crystallization temperature resulting in phases closer to metastable equilibrium, and initiated clustered crystallization for [MoO$_3$]> 2.5 mol%. β-irradiation was found to have favorable properties in amorphous systems by creating structural disorder and defect assisted ion migration that thus prevented crystallization. It also increased reticulation in the borosilicate network through 6-membered boroxyl ring and Si ring cleavage to form smaller rings and isolated units. This occurred alongside an increased reduction of Mo$^{6+}$with dose that can be correlated to molybdenum solubility. In compositions with existing CaMoO$_4$ crystallites, radiation caused a scattering effect, though the crystal content remained unchanged. Therefore β-irradiation can preferentially prevent crystallization in calcium borosilicates for [MoO$_3$] < 2.5 mol%, but has a smaller impact on systems with existing CaMoO$_4$ crystallites. (10.1016/j.jnoncrysol.2017.06.018)
  DOI : 10.1016/j.jnoncrysol.2017.06.018
• Time-resolved photoemission spectroscopy of electronic cooling and localization in CH$_3$ NH$_3$ PbI$_3$ crystals
  
  • Chen Zhesheng
  • Lee Min-I
  • Zhang Zailan
  • Diab Hiba
  • Garrot Damien
  • Lédée Ferdinand
  • Fertey Pierre
  • Papalazarou Evangelos
  • Marsi Marino
  • Ponseca Carlito
  • Deleporte Emmanuelle
  • Tejeda Antonio
  • Perfetti Luca
  Physical Review Materials, American Physical Society, 2017, 1 (4), pp.045402. We measure the surface of CH$_3$ NH$_3$ PbI$_3$ single crystals by making use of two photon photoemission spectroscopy. Our method monitors the electronic distribution of photoexcited electrons, explicitly discriminating the initial thermalization from slower dynamical processes. The reported results disclose the fast dissipation channels of hot carriers (0.25 ps), set a upper bound to the surface induced recombination velocity (< 4000 cm/s) and reveal the dramatic effect of shallow traps on the electrons dynamics. The picosecond localization of excited electrons in degraded CH$_3$ NH$_3$ PbI$_3$ samples is consistent with the progressive reduction of photoconversion efficiency in operating devices. Minimizing the density of shallow traps and solving the aging problem may boost the macroscopic efficiency of solar cells to the theoretical limit. (10.1103/PhysRevMaterials.1.045402)
  DOI : 10.1103/PhysRevMaterials.1.045402
• β-irradiation effects on the formation and stability of CaMoO$_4 in a soda lime borosilicate glass ceramic for nuclear waste storage
  
  • Patel Karishma B.
  • Boizot Bruno
  • Facq Sébastien P.
  • Lampronti Giulio I.
  • Peuget Sylvain
  • Schuller Sophie
  • Farnan Ian
  Inorganic Chemistry, American Chemical Society, 2017, 56 (3), pp.1558 - 1573. Molybdenum solubility is a limiting factor to actinide loading in nuclear waste glasses, as it initiates the formation of water-soluble crystalline phases such as alkali molybdates. To increase waste loading efficiency, alternative glass ceramic structures are sought that prove resistant to internal radiation resulting from radioisotope decay. In this study, selective formation of water-durable CaMoO$_4$ in a soda lime borosilicate is achieved by introducing up to 10 mol % MoO$_3$ in a 1:1 ratio to CaO using a sintering process. The resulting homogeneously dispersed spherical CaMoO$_4$ nanocrystallites were analyzed using electron microscopy, X-ray diffraction (XRD), Raman and electron paramagnetic resonance (EPR) spectroscopies prior to and post irradiation, which replicated internal β-irradiation damage on an accelerated scale. Following 0.77 to 1.34 GGy of 2.5 MeV electron radiation CaMoO$_4$ does not exhibit amorphization or significant transformation. Nor does irradiation induce glass-in-glass phase separation in the surrounding amorphous matrix, or the precipitation of other molybdates, thus proving that excess molybdenum can be successfully incorporated into a structure that it is resistant to β-irradiation proportional to 1000 years of storage without water-soluble byproducts. The CaMoO$_4$ crystallites do however exhibit a nonlinear Scherrer crystallite size pattern with dose, as determined by a Rietveld refinement of XRD patterns and an alteration in crystal quality as deduced by anisotropic peak changes in both XRD and Raman spectroscopy. Radiation-induced modifications in the CaMoO$_4$ tetragonal unit cell occurred primarily along the c-axis indicating relaxation of stacked calcium polyhedra. Concurrently, a strong reduction of Mo$^{6+}$ to Mo$^{5+}$ during irradiation is observed by EPR, which is believed to enhance Ca mobility. These combined results are used to hypothesize a crystallite size alteration model based on a combination of relaxation and diffusion-based processes initiated by added energy from β-impingement and second-order structural modifications induced by defect accumulation. (10.1021/acs.inorgchem.6b02657)
  DOI : 10.1021/acs.inorgchem.6b02657