Exchange of a Tetrapositive Cation into a Zeolite and a New Inorganic Scintillator. I. Crystal Structures and Scintillation Properties of Anhydrous Zr_1.7Tl_5.4Cl_1.7-LTA and Zr_2.1Tl_1.6Cl_3.0-LTA

Abstract A new inorganic scintillator has been prepared by the assembly of thallium, zirconium, and chloride ions in a zeolite. Also, for the first time, a 4+ cation has been exchanged directly into a zeolite. From |Na₁₂(H₂O)_x|[Si₁₂Al₁₂O₄₈]-A (zeolite LTA), |Zr_1.7Tl_5.4Cl_1.7|[Si_13.5Al_10.5O₄₈]-A and |Zr_2.1Tl_1.6Cl_3.0|[Si_17.4Al_6.6O₄₈]-A were prepared by the thallous ion exchange (TIE) method: fully dehydrated Tl₁₂-A was treated with ZrCl₄ (g, 3.7 × 10³ Pa) at 553 and 623 K, respectively. Their crystal structures were determined by single-crystal crystallography using synchrotron X-radiation and their compositions were partially confirmed by SEM-EDX analyses. Their structures were refined in the space group Pm3m (a = 12.215(1) and 11.945(1) Å) with all unique data to the final error indices R₁ = 0.047 and 0.075 for the 680 and 380 reflections for which F_o > 4σ(F_o), respectively. Extraframework Zr⁴⁺ and Zr²⁺ ions had replaced some of the Tl⁺ ions in Tl₁₂-A. Some Zr⁴⁺ ions are 4-coordinate with three bonds to framework oxygen atoms and one to a Cl^- ion; others are 5-coordinate, bonding to two Cl^- ions. Tetrahedral Zr²⁺ was found as ZrCl₄^2- in |Zr_2.1Tl_1.6Cl_3.0|[Si_17.4Al_6.6O₄₈]-A; each of its Cl^- ions bonds linearly to a Zr⁴⁺ ion, which in turn bonds linearly to another Cl^- ion to form Zr₅Cl₈¹⁰⁺ clusters centered in and extending out of the sodalite cavities. The Tl⁺ ions are in the large cavities. The X-ray induced emission spectrum of Zr,Tl,Cl-A has a broad band between 330 and 750 nm, peaking at 490 nm. The integrated light yield observed for Zr,Tl,Cl-A powder is about five times greater than that of anthracene, a well documented scintillator. This strong radioluminescence appears to be due to the simultaneous presence of Zr and Tl within the zeolite.