Photon Factory Activity Report 2016 #34 (2017)

BL-5A/2016G677

Crystal Structure and Scintillation Properties of Cs,Na-LTA
Treated with Zirconium Chloride Vapor
Chung Woo Lee1, Joon Young Kim2, Nam Ho Heo2,*, and Karl Seff3
Korea Research Institute of Chemical Technology, Yuseong, Daejeon 34114, Korea
2
Laboratory of Structural Chemistry, Department of Applied Chemical Engineering, Kyungpook NationalUniversity, Daegu 41566, Korea
3
Department of Chemistry, University of Hawaii, 2545 The Mall, Honolulu, Hawaii 96822, U. S. A1

1 Introduction
Cs+ ions assembled with X-ray absorbers like Zr or Hf,e.g., Cs2ZrCl6 and Cs2HfCl6, had scintillation properties[1]. Zeolites, because of their molecular dimensioned
channels and cavities, can host relatively small molecules,
relatively large cations, and continua. A broader range ofcompositions can be assembled within zeolites than thoseof pure and doped compounds, and this could lead tobetter scintillators. In this study, we expected that ZrCl4
would be readily sorbed at a moderate temperature (523K), where the vapor pressure of ZrCl4 is reasonably high(3.7 X 103 Pa) and dehydrated Cs,Na-A is stable[2]. Zr4+
would be readily identifiable crystallographically because
its ionic radius and scattering power are very different
from those of any of the other ions in the expected
product Zr,Cl,Cs,Na-A.
2 Experiment
Large colorless transparent single crystals of zeolite A(|Na12(H2O)x|[Si12Al12O48]–LTA, Na12–A∙xH2O, or Na–A)
was lodged in a thin Pyrex capillary. Aqueous CsC2H3O2(sigma-Aldrich, 99.99%+) (pH = 6.2) allowed to flow
past it (dynamic ion exchange). A break-off sealed tube
with anhydrous ZrCl4 (sigma-Aldrich, 99.99%) wasattached as a hydrated Cs,Na-A crystal prepared as above.
After this crystal was fully dehydrated, the reaction vessel(the capillary containing the crystal, the tube above it, andthe side arm containing the anhydrous ZrCl4) was sealed
off from the vacuum line. The internal seal was thenbroken and the ZrCl4 was transferred to the tube. Finally,
the side arm was sealed off. The resulting linear reaction
vessel was heated to allow ZrCl4(g) to react with thezeolite. The diffraction intensities for the crystal wasmeasured with synchrotron X-radiation at the BL-5A
beam line of the Photon Factory, KEK, Japan.
3 Results and Discussion|Zr0.14Cs5.69Na4.13Cl0.85|[Si12Al12O48]–A(approximate
formula, Table 1) was determined by single-crystal
crystallography using synchrotron X-radiation. The
structure of Zr,Cl,Cs,Na-A was refined in the space groupPm 3 m (a = 12.230(1) Å) with all unique data to the final
error index R1 = 0.069 for the 639 reflections for which
Fo > 4σ(Fo). Octahedral ZrCl62- ions center 14% of thelarge cavities; each Cl- ion bonds to an 8-ring Cs+ ion(See Fig. 1). These Cs+ ions bridge between ZrCl62- ionsto form a continuum with unit cell formula Cs3ZrCl6+ inthe near-surface volume of the crystal. Other Cs+ ions lie

opposite 6-rings in the sodalite and large cavities. Upon
X-irradiation Zr,Cl,Cs,Na-A luminesces bright sky blue;
the emission band is broad, ranging from 370 to 750 nm,
peaking at 480 nm (See Fig. 2).
Table 1: Assignment of Oxidation States and Charge BudgetAtomionsa
occupancybr,cÅ
NCd
ΣCharges+
Cs1
Cs
3.0
2.06
43.0
Cs2
Cs+
0.74(4)1.79
30.74(4)+Cs3
Cs+
0.82(14)1.50
30.82(14)+Cs4
Cs+
1.13(14)
1.69
31.13(14)+Na1Na+
4.13(15)
0.93
34.13(15)+Zr
Zr4+
0.142(17)60.59(7)+ClCl0.85(10)20.85(10)ΣCs = 5.69(20) ΣNa = 4.13(15)Σ charges = 9.6(3)+ΣZr = 0.142(17), ΣCl = 0.85(10)aExtraframework ions bOccupancy, ions per unit cell. cRadii ofM ions obtained by subtracting 1.32 Å from the shortest M-Obond lengths. dCoordination numbers.

Fig. 1: Complexes and clusters in Zr,Cl,Cs,Na-A; (a) ZrCl62and (b) the Zr(ClCs)64+ unit associated further with eightsurrounding Cs+ ions.

Fig. 2: Visible spectra of dehydrated Zr,Cl,Cs,Na-A powder andrelated materials upon irradiation with polychromatic X-rays(Cu target, 100 kV, 2mA)

References[1] P. Bryan et al., J. Lumin 31, 117 (1984).
[2] Jr. T. Vance et al., J. Phys. Chem 79, 2163 (1975).
* nhheo@knu.ac.kr