207Pb and 205TI NMR on Perovskite Type Crystals APbX3 (A = Cs, Tl, X = Br, I)

Abstract

By 205T1 and 207Pb NMR the chemical shift in polycrystalline samples of binary halides AX, BX2 and ternary halides ABX3 (A = Cs, Tl; B = Pb; X = Br, I) was studied at room temperature. The chemical shift tensors δ (205Tl) and δ (207Pb) were determined in magnitude and orientation on single crystals of the orthorhombic TlPbI3. The components of the δ(205Tl) tensor are: δx(205T1) || a = 611 ppm; δy(205T1) || b = 680 ppm; δz(205Tl) || c = 1329 ppm; δiso(205Tl) = 873.3 ppm (with respect to 3.4 molar aqueous solution of TlÖOCCH3). The chemical shift tensor of 207Pb in TlPbI3 shows two orientations. One of them is: δx(207Pb) = 3760 ppm, inclined 30: from b towards c, δy(207Pb) || a = 3485 ppm, δz(207Pb) = 2639 ppm inclined 120° from b towards c. δiso(207Pb)-3295 ppm (with respect to saturated aqueous solution of Pb(NO3)2). The results are discussed with respect to the crystal structure and a model to explain orientation and anisotropy of the tensors δ(205Tl) and δ(207Pb) in TlPbI3 is proposed. In the system CsPbBr3_xIx δ(207Pb) was studied on polycrystalline samples. The chemical shift increases with increasing x and negative excess shift is observed. © 1987, Walter de Gruyter. All rights reserved.