D. Zanghi - Academia.edu (original) (raw)

Papers by D. Zanghi

Infrared Physics & Technology

Non-Crystalline and Nanoscale Materials, 1998

ABSTRACT Using time resolved x-ray diffraction combined with aerodynamic levita-tion and CO 2 las... more ABSTRACT Using time resolved x-ray diffraction combined with aerodynamic levita-tion and CO 2 laser heating, we have studied the structural evolution of the fragile glass-forming liquid CaAl 2 O 4 during supercooling from the stable liquid phase to the cold glass below T g . In particular, we followed the evolution of the structure factor S(Q) and of the corresponding pair distribution function g(r). The results show significant structural changes around 1.25 T g indicating an increase in the degree of both inter-mediate-and short-range order occurring close to the dynamical crossover temperature. Experiments were carried out at several beamlines at various synchrotron sources and we show that the potential of third generation synchrotron beamlines is limited by the lack of efficient detectors for making time resolved measurements on disordered materials. In this paper, we present an overview of the advances performed in this area over the past 10 years pointing out the limitations and expectations for the near future.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1999

Films of ZrN were prepared using Zr sputtering assisted by N bombardment on heated substrates. Th... more Films of ZrN were prepared using Zr sputtering assisted by N bombardment on heated substrates. They were submitted to Co implantation at 300 K with various¯uences to reach concentrations as high as 10%±30% in the doped zone. The long and short range orders were studied via X-ray absorption spectroscopy performed at the Zr and Co K edges and X-ray diraction. ZrN appears stable under the amount of energy deposited in the lattice, no amorphization is observed. Co ions precipitate to form clusters. This is interpreted as due to the great stability of the matrix together with the fact that Co±N bonds are not chemically favoured. Such a precipitation was already seen in the case of Cu and Ni implantation in the AlN matrix.

Journal of Synchrotron Radiation, 2001

Si3N4 amorphous thin layers prepared by sputtering have been implanted either with Cu or with Fe ... more Si3N4 amorphous thin layers prepared by sputtering have been implanted either with Cu or with Fe ions. X-ray absorption spectroscopy was performed at the Si K edge to characterise the electronic empty states of p character, the structural state of the initial layers and the modifications around Si induced by implantation and a post-annealing treatment. We show that the energy deposition process mainly leads to a reorganisation of the second coordination shell around Si, i.e. concerns the Si-Si bonds.

Journal of Synchrotron Radiation, 2001

AlN bulk ceramic has been implanted with energetic Co ions. In order to accurately characterise t... more AlN bulk ceramic has been implanted with energetic Co ions. In order to accurately characterise the atomic surrounding of the implanted ions, X-ray absorption measurements were carried out at 80 K in the fluorescence mode at the Co K edge in the as-implanted and annealed states. Simulation of the EXAFS oscillations allowed us to identify a first stage where Co is inserted in the AlN matrix followed by a second stage where Co precipitates form.

Journal of Physics: Condensed Matter, 1998

Magnetic Ni clusters, with an average diameter of 1.9 nm, were prepared by ion implantation in a ... more Magnetic Ni clusters, with an average diameter of 1.9 nm, were prepared by ion implantation in a sintered AlN matrix. X-ray magnetic circular dichroism measurements were performed on this sample at 100 K and 300 K, by measuring the edges of Ni under a magnetic field of T. Using the sum rules currently applied to the bulk transition metals, we deduce a total magnetic moment and the orbital and spin contributions to this moment. The magnetic moment is in good agreement with the values measured by SQUID magnetometry at the same temperatures.

Journal of Materials Research, 2010

Synchrotron x-ray μ-tomography has been used to reconstruct the three-dimensional view of a rough... more Synchrotron x-ray μ-tomography has been used to reconstruct the three-dimensional view of a rough surface extracted from a heterogeneous ceramic coating composed of Pr2NiO4+δ. Radiographs with a resolution of 0.7 μm have been recorded at T = 300, 600, and 900 K. The analysis of surface geometry makes use of the geometrical optic approximation up to T = 900 K possible. Subsequently, a large number of rays (105) are impinged onto the numerical surface, as revealed by x-ray tomography, to reproduce the normal emissivity of the coating. This normal emissivity was obtained beforehand by infrared emittance spectroscopy at T = 1000 K. Comparison of the two approaches suggests that the optical contribution of the coating micropores can be integrated into the ray tracing code. The effective medium approximation is used for this purpose. Finally, the applicability of this hybrid approach is discussed.

Journal of Materials Research, 2001

Ti, Fe, and Co ions were implanted in two ceramics, SiC and Si3N4, to reach concentrations on the... more Ti, Fe, and Co ions were implanted in two ceramics, SiC and Si3N4, to reach concentrations on the order of 10% over a depth of about 50–60 nm. X-ray absorption spectroscopy was performed at the K edge of the implanted ions to identify their local environment at the end of the implantation process. Ti was found to form Ti–C and Ti–N bonds whereas Co and Fe precipitated and formed clusters in Si3N4. CoSi was detected in SiC whereas, in the same matrix, Fe clusters coexist with FeSi. A coherent interpretation of these results is given in terms of the heat of reaction for all possible systems. We also successfully interpret in the same way some results found in literature in the case of implanted oxides.

Journal of Applied Physics, 2001

... Phys. Rev. B 42, 1582 (1990). Zs. Kovács, L. Kövér, P. Weightman, D. Varga, R. Sanjnés, J. Pá... more ... Phys. Rev. B 42, 1582 (1990). Zs. Kovács, L. Kövér, P. Weightman, D. Varga, R. Sanjnés, J. Pálinkás, G. Margaritondo, and H. Adachi, “Electronic structure of Al[sub 3]Ni and AlNi[sub 3] alloys,” Phys. Rev. B 54, 8501 (1996). D ...

EPL (Europhysics Letters), 2008

ABSTRACT Small Ni, Cu, Fe, Ag, Pt, Au nanoparticles with average diameters in the nanometer range... more ABSTRACT Small Ni, Cu, Fe, Ag, Pt, Au nanoparticles with average diameters in the nanometer range have been studied by infrared spectroscopy. The Ni, Cu, Fe, Ag, Au nanoparticles were embedded in transparent matrices, AlN or Si3N4, or deposited on Si3N4 in the case of Pt. They were previously characterized by several techniques such as X-ray absorption spectroscopy, grazing incidence small-angle X-ray scattering or transmission electron microscopy. Infrared absorption depending on the metal is detected in the 60 meV to 140 meV energy range. It is interpreted as due to low-energy collective electron excitations related to the 2D confinement occurring at the metal-matrix interface.

The European Physical Journal D, 2000

: Ni ions were implanted in bulk AlN with the goal to form embedded metallic clusters. Combinin... more : Ni ions were implanted in bulk AlN with the goal to form embedded metallic clusters. Combining several characterisation techniques such as X-ray absorption spectroscopy, X-ray diffraction and high resolution transmission electron microscopy, we determined the lattice parameter of the Ni clusters that display a fcc crystalline structure. The average size increases when the ion fluence is increased or after

Y2O3-Al2O3 compounds doped with rare earth elements are used in pumped lasers [1] or scintillator... more Y2O3-Al2O3 compounds doped with rare earth elements are used in pumped lasers [1] or scintillators [2]. However, their aptitude to vitrify is quite low compared to other aluminate glasses. They can not be elaborated using the classical melting-quenching process, in a ...

Journal of Applied Physics, 2001

... nanosized particles, the clusters size being controlled by the ion fluence (followed by a the... more ... nanosized particles, the clusters size being controlled by the ion fluence (followed by a thermal treatment) and the ... YP Lee, KW Kim, JY Rhee, and YV Kudryavtsev, “Influence of structural disorder on the temperature dependence of the transport and magnetic properties of ...

AIP Conference Proceedings, 2003

Display structures suitable for direct growth of CNT films by thermal CVD are described. The CNT ... more Display structures suitable for direct growth of CNT films by thermal CVD are described. The CNT film specifications for TV application are the following: a threshold field for emission higher than 3 V/µm, a current density of 140mA/cm 2 and an emission site density around 10 7 cm -2 . The major difficulty encountered with the deposited films is to reach the specified emission site density. These films present an exponential distribution of the amplification factor controlling the current emission. Small 1 cm 2 working displays with CNTs grown by using the decomposition of C2H2 over Ni catalyst have been done. These samples show that the three major locks of conventional FED technology, namely large size compatibility, simple low cost cathode and good reliability, are now opening thanks to CNTs.

Gaune-Escard/Molten Salts Chemistry and Technology, 2014

ABSTRACT Our original approach consists in coupling, in situ at high temperature, NMR (nuclear ma... more ABSTRACT Our original approach consists in coupling, in situ at high temperature, NMR (nuclear magnetic resonance) and EXAFS (extended X-ray absorption fine structure) techniques, both sensitive to the local environment of a selected element and able to follow the evolution of ionic species in the melt with composition and temperature. We focussed on the study of rare earth fluoride solubility, starting with LaF3, in molten LiF-ZrF4 mixtures. We studied the NMR signal evolution of 19F, 139La, and 91Zr in situ in the melt at high temperature. Compared to the binary LiF-ZrF4, NMR experiments do not show any difference in 19F chemical shift evolution. The NMR signal of zirconium is only slightly shifted. This corresponds to a weak evolution of the average coordination around Zr. This is confirmed by in situ EXAFS experiments at the K-edge of Zr. In LiF-ZrF4-LaF3 with 5 mol% of LaF3, 139La chemical shift strongly increases with ZrF4 content. This evolution is associated with an important modification of the local environment around the lanthanum. It can be correlated to an important increase of its coordination number or to the influence of zirconium atoms in its second sphere of coordination.

REVIEW OF SCIENTIFIC INSTRUMENTS, 2006

We describe a new high temperature environment based on aerodynamic levitation and laser heating ... more We describe a new high temperature environment based on aerodynamic levitation and laser heating designed for neutron scattering experiments up to 3000°C. The sample is heated to the desired temperature with three CO 2 lasers from different directions in order to obtain a homogeneous temperature distribution. The apparent temperature of the sample is measured with an optical pyrometer, and two video cameras are employed to monitor the sample behavior during heating. The levitation setup is enclosed in a vacuum-tight chamber, enabling a high degree of gas purity and a reproducible sample environment for structural investigations on both oxide and metallic melts. High-quality neutron diffraction data have been obtained on liquid Y 3 Al 5 O 12 and ZrNi alloy for relatively short counting times ͑1.5 h͒.

Molten Salts and Ionic Liquids 17, 2010

ABSTRACT We study the nature and the distribution of the different anionic species existing in fl... more ABSTRACT We study the nature and the distribution of the different anionic species existing in fluoride melts of nuclear interest. Our approach is based on the combination of NMR and EXAFS spectroscopy, both sensitive to the microstructure of the melt, with Molecular Dynamics calculations. Because of its analogy with actinide fluorides, we have studied zirconium fluoride and its mixtures with alkali fluorides. In MF-ZrF4 systems, MD simulations, in agreement with Zr-91 and F-19 NMR and EXAFS experiments, put in evidence the coexistence of 3 different Zr-based complexes [ZrF6](2-), [ZrF7](3-), and [ZrF8](4-) in the melt. Their proportions depend on the amount of ZrF4 and on the nature of the alkali (Li+, Na+ and K+). In the case of lanthanide fluorides, a similar approach performed in the system MF-LaF3 evidences some structural similarity, mainly with the existence of different complexes and upon free fluorine content evolution.

The Journal of Physical Chemistry B, 2011

The structure of AF-ZrF(4) system (A(+) = Li(+), Na(+), K(+)) compounds in the liquid state is st... more The structure of AF-ZrF(4) system (A(+) = Li(+), Na(+), K(+)) compounds in the liquid state is studied using an approach combining EXAFS spectroscopy with molecular dynamics simulations. A very good agreement is observed between the two techniques, which allows us to propose a quantitative description of the liquids. From the Zr(4+) solvation shell point of view, we observe a progressive stabilization of the 7-fold and then of the 6-fold coordinated complexes when passing from Li(+) to Na(+) and K(+) as a "counterion". Particular attention is given to the systems consisting of 35 mol % of ZrF(4). At that particular composition, the ZrF(6)(2-) complex predominates largely whatever the nature of the alkali. The calculated vibrational properties of this complex are in excellent agreement with a previous Raman spectroscopy experiment on molten KF-ZrF(4). The most important differences are observed for the lifetime of these octahedral units, which increases importantly with the size of the monovalent cation. On a larger scale, an intense first sharp diffraction peak is observed for the Zr(4+)-Zr(4+) partial structure factor, which can be attributed to the correlations between the octahedral units formed.

Infrared Physics & Technology

Non-Crystalline and Nanoscale Materials, 1998

ABSTRACT Using time resolved x-ray diffraction combined with aerodynamic levita-tion and CO 2 las... more ABSTRACT Using time resolved x-ray diffraction combined with aerodynamic levita-tion and CO 2 laser heating, we have studied the structural evolution of the fragile glass-forming liquid CaAl 2 O 4 during supercooling from the stable liquid phase to the cold glass below T g . In particular, we followed the evolution of the structure factor S(Q) and of the corresponding pair distribution function g(r). The results show significant structural changes around 1.25 T g indicating an increase in the degree of both inter-mediate-and short-range order occurring close to the dynamical crossover temperature. Experiments were carried out at several beamlines at various synchrotron sources and we show that the potential of third generation synchrotron beamlines is limited by the lack of efficient detectors for making time resolved measurements on disordered materials. In this paper, we present an overview of the advances performed in this area over the past 10 years pointing out the limitations and expectations for the near future.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1999

Films of ZrN were prepared using Zr sputtering assisted by N bombardment on heated substrates. Th... more Films of ZrN were prepared using Zr sputtering assisted by N bombardment on heated substrates. They were submitted to Co implantation at 300 K with various¯uences to reach concentrations as high as 10%±30% in the doped zone. The long and short range orders were studied via X-ray absorption spectroscopy performed at the Zr and Co K edges and X-ray diraction. ZrN appears stable under the amount of energy deposited in the lattice, no amorphization is observed. Co ions precipitate to form clusters. This is interpreted as due to the great stability of the matrix together with the fact that Co±N bonds are not chemically favoured. Such a precipitation was already seen in the case of Cu and Ni implantation in the AlN matrix.

Journal of Synchrotron Radiation, 2001

Si3N4 amorphous thin layers prepared by sputtering have been implanted either with Cu or with Fe ... more Si3N4 amorphous thin layers prepared by sputtering have been implanted either with Cu or with Fe ions. X-ray absorption spectroscopy was performed at the Si K edge to characterise the electronic empty states of p character, the structural state of the initial layers and the modifications around Si induced by implantation and a post-annealing treatment. We show that the energy deposition process mainly leads to a reorganisation of the second coordination shell around Si, i.e. concerns the Si-Si bonds.

Journal of Synchrotron Radiation, 2001

AlN bulk ceramic has been implanted with energetic Co ions. In order to accurately characterise t... more AlN bulk ceramic has been implanted with energetic Co ions. In order to accurately characterise the atomic surrounding of the implanted ions, X-ray absorption measurements were carried out at 80 K in the fluorescence mode at the Co K edge in the as-implanted and annealed states. Simulation of the EXAFS oscillations allowed us to identify a first stage where Co is inserted in the AlN matrix followed by a second stage where Co precipitates form.

Journal of Physics: Condensed Matter, 1998

Magnetic Ni clusters, with an average diameter of 1.9 nm, were prepared by ion implantation in a ... more Magnetic Ni clusters, with an average diameter of 1.9 nm, were prepared by ion implantation in a sintered AlN matrix. X-ray magnetic circular dichroism measurements were performed on this sample at 100 K and 300 K, by measuring the edges of Ni under a magnetic field of T. Using the sum rules currently applied to the bulk transition metals, we deduce a total magnetic moment and the orbital and spin contributions to this moment. The magnetic moment is in good agreement with the values measured by SQUID magnetometry at the same temperatures.

Journal of Materials Research, 2010

Synchrotron x-ray μ-tomography has been used to reconstruct the three-dimensional view of a rough... more Synchrotron x-ray μ-tomography has been used to reconstruct the three-dimensional view of a rough surface extracted from a heterogeneous ceramic coating composed of Pr2NiO4+δ. Radiographs with a resolution of 0.7 μm have been recorded at T = 300, 600, and 900 K. The analysis of surface geometry makes use of the geometrical optic approximation up to T = 900 K possible. Subsequently, a large number of rays (105) are impinged onto the numerical surface, as revealed by x-ray tomography, to reproduce the normal emissivity of the coating. This normal emissivity was obtained beforehand by infrared emittance spectroscopy at T = 1000 K. Comparison of the two approaches suggests that the optical contribution of the coating micropores can be integrated into the ray tracing code. The effective medium approximation is used for this purpose. Finally, the applicability of this hybrid approach is discussed.

Journal of Materials Research, 2001

Ti, Fe, and Co ions were implanted in two ceramics, SiC and Si3N4, to reach concentrations on the... more Ti, Fe, and Co ions were implanted in two ceramics, SiC and Si3N4, to reach concentrations on the order of 10% over a depth of about 50–60 nm. X-ray absorption spectroscopy was performed at the K edge of the implanted ions to identify their local environment at the end of the implantation process. Ti was found to form Ti–C and Ti–N bonds whereas Co and Fe precipitated and formed clusters in Si3N4. CoSi was detected in SiC whereas, in the same matrix, Fe clusters coexist with FeSi. A coherent interpretation of these results is given in terms of the heat of reaction for all possible systems. We also successfully interpret in the same way some results found in literature in the case of implanted oxides.

Journal of Applied Physics, 2001

... Phys. Rev. B 42, 1582 (1990). Zs. Kovács, L. Kövér, P. Weightman, D. Varga, R. Sanjnés, J. Pá... more ... Phys. Rev. B 42, 1582 (1990). Zs. Kovács, L. Kövér, P. Weightman, D. Varga, R. Sanjnés, J. Pálinkás, G. Margaritondo, and H. Adachi, “Electronic structure of Al[sub 3]Ni and AlNi[sub 3] alloys,” Phys. Rev. B 54, 8501 (1996). D ...

EPL (Europhysics Letters), 2008

ABSTRACT Small Ni, Cu, Fe, Ag, Pt, Au nanoparticles with average diameters in the nanometer range... more ABSTRACT Small Ni, Cu, Fe, Ag, Pt, Au nanoparticles with average diameters in the nanometer range have been studied by infrared spectroscopy. The Ni, Cu, Fe, Ag, Au nanoparticles were embedded in transparent matrices, AlN or Si3N4, or deposited on Si3N4 in the case of Pt. They were previously characterized by several techniques such as X-ray absorption spectroscopy, grazing incidence small-angle X-ray scattering or transmission electron microscopy. Infrared absorption depending on the metal is detected in the 60 meV to 140 meV energy range. It is interpreted as due to low-energy collective electron excitations related to the 2D confinement occurring at the metal-matrix interface.

The European Physical Journal D, 2000

: Ni ions were implanted in bulk AlN with the goal to form embedded metallic clusters. Combinin... more : Ni ions were implanted in bulk AlN with the goal to form embedded metallic clusters. Combining several characterisation techniques such as X-ray absorption spectroscopy, X-ray diffraction and high resolution transmission electron microscopy, we determined the lattice parameter of the Ni clusters that display a fcc crystalline structure. The average size increases when the ion fluence is increased or after

Y2O3-Al2O3 compounds doped with rare earth elements are used in pumped lasers [1] or scintillator... more Y2O3-Al2O3 compounds doped with rare earth elements are used in pumped lasers [1] or scintillators [2]. However, their aptitude to vitrify is quite low compared to other aluminate glasses. They can not be elaborated using the classical melting-quenching process, in a ...

Journal of Applied Physics, 2001

... nanosized particles, the clusters size being controlled by the ion fluence (followed by a the... more ... nanosized particles, the clusters size being controlled by the ion fluence (followed by a thermal treatment) and the ... YP Lee, KW Kim, JY Rhee, and YV Kudryavtsev, “Influence of structural disorder on the temperature dependence of the transport and magnetic properties of ...

AIP Conference Proceedings, 2003

Display structures suitable for direct growth of CNT films by thermal CVD are described. The CNT ... more Display structures suitable for direct growth of CNT films by thermal CVD are described. The CNT film specifications for TV application are the following: a threshold field for emission higher than 3 V/µm, a current density of 140mA/cm 2 and an emission site density around 10 7 cm -2 . The major difficulty encountered with the deposited films is to reach the specified emission site density. These films present an exponential distribution of the amplification factor controlling the current emission. Small 1 cm 2 working displays with CNTs grown by using the decomposition of C2H2 over Ni catalyst have been done. These samples show that the three major locks of conventional FED technology, namely large size compatibility, simple low cost cathode and good reliability, are now opening thanks to CNTs.

Gaune-Escard/Molten Salts Chemistry and Technology, 2014

ABSTRACT Our original approach consists in coupling, in situ at high temperature, NMR (nuclear ma... more ABSTRACT Our original approach consists in coupling, in situ at high temperature, NMR (nuclear magnetic resonance) and EXAFS (extended X-ray absorption fine structure) techniques, both sensitive to the local environment of a selected element and able to follow the evolution of ionic species in the melt with composition and temperature. We focussed on the study of rare earth fluoride solubility, starting with LaF3, in molten LiF-ZrF4 mixtures. We studied the NMR signal evolution of 19F, 139La, and 91Zr in situ in the melt at high temperature. Compared to the binary LiF-ZrF4, NMR experiments do not show any difference in 19F chemical shift evolution. The NMR signal of zirconium is only slightly shifted. This corresponds to a weak evolution of the average coordination around Zr. This is confirmed by in situ EXAFS experiments at the K-edge of Zr. In LiF-ZrF4-LaF3 with 5 mol% of LaF3, 139La chemical shift strongly increases with ZrF4 content. This evolution is associated with an important modification of the local environment around the lanthanum. It can be correlated to an important increase of its coordination number or to the influence of zirconium atoms in its second sphere of coordination.

REVIEW OF SCIENTIFIC INSTRUMENTS, 2006

We describe a new high temperature environment based on aerodynamic levitation and laser heating ... more We describe a new high temperature environment based on aerodynamic levitation and laser heating designed for neutron scattering experiments up to 3000°C. The sample is heated to the desired temperature with three CO 2 lasers from different directions in order to obtain a homogeneous temperature distribution. The apparent temperature of the sample is measured with an optical pyrometer, and two video cameras are employed to monitor the sample behavior during heating. The levitation setup is enclosed in a vacuum-tight chamber, enabling a high degree of gas purity and a reproducible sample environment for structural investigations on both oxide and metallic melts. High-quality neutron diffraction data have been obtained on liquid Y 3 Al 5 O 12 and ZrNi alloy for relatively short counting times ͑1.5 h͒.

Molten Salts and Ionic Liquids 17, 2010

ABSTRACT We study the nature and the distribution of the different anionic species existing in fl... more ABSTRACT We study the nature and the distribution of the different anionic species existing in fluoride melts of nuclear interest. Our approach is based on the combination of NMR and EXAFS spectroscopy, both sensitive to the microstructure of the melt, with Molecular Dynamics calculations. Because of its analogy with actinide fluorides, we have studied zirconium fluoride and its mixtures with alkali fluorides. In MF-ZrF4 systems, MD simulations, in agreement with Zr-91 and F-19 NMR and EXAFS experiments, put in evidence the coexistence of 3 different Zr-based complexes [ZrF6](2-), [ZrF7](3-), and [ZrF8](4-) in the melt. Their proportions depend on the amount of ZrF4 and on the nature of the alkali (Li+, Na+ and K+). In the case of lanthanide fluorides, a similar approach performed in the system MF-LaF3 evidences some structural similarity, mainly with the existence of different complexes and upon free fluorine content evolution.

The Journal of Physical Chemistry B, 2011

The structure of AF-ZrF(4) system (A(+) = Li(+), Na(+), K(+)) compounds in the liquid state is st... more The structure of AF-ZrF(4) system (A(+) = Li(+), Na(+), K(+)) compounds in the liquid state is studied using an approach combining EXAFS spectroscopy with molecular dynamics simulations. A very good agreement is observed between the two techniques, which allows us to propose a quantitative description of the liquids. From the Zr(4+) solvation shell point of view, we observe a progressive stabilization of the 7-fold and then of the 6-fold coordinated complexes when passing from Li(+) to Na(+) and K(+) as a "counterion". Particular attention is given to the systems consisting of 35 mol % of ZrF(4). At that particular composition, the ZrF(6)(2-) complex predominates largely whatever the nature of the alkali. The calculated vibrational properties of this complex are in excellent agreement with a previous Raman spectroscopy experiment on molten KF-ZrF(4). The most important differences are observed for the lifetime of these octahedral units, which increases importantly with the size of the monovalent cation. On a larger scale, an intense first sharp diffraction peak is observed for the Zr(4+)-Zr(4+) partial structure factor, which can be attributed to the correlations between the octahedral units formed.