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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on KPb2Cl5 by Materials Project

KPb2Cl5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. K1+ is bonded in a 9-coordinate geometry to nine Cl1- atoms. There are a spread of K–Cl bond distances ranging from 3.24–3.86 Å. There are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 8-coordinate geometry to eight Cl1- atoms. There are a spread of Pb–Cl bond distances ranging from 2.88–3.60 Å. In the second Pb2+ site, Pb2+ is bonded to seven Cl1- atoms to form distorted edge-sharing PbCl7 pentagonal bipyramids. There are a spread of Pb–Cl bond distances ranging from 2.87–3.25 Å. There are five inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded to four Pb2+ atoms to form distorted ClPb4 trigonal pyramids that share corners with four equivalent ClK2Pb3 trigonal bipyramids, corners with two equivalent ClPb4 trigonal pyramids, an edgeedge with one ClK2Pb3 trigonal bipyramid, and an edgeedge with one ClPb4 trigonal pyramid. In the second Cl1- site, Cl1- is bonded to two equivalent K1+ and three Pb2+ atoms to form distorted ClK2Pb3 trigonal bipyramids that share corners with four equivalent ClPb4 trigonal pyramids, edges with two equivalent ClK2Pb3 trigonal bipyramids, and an edgeedge with one ClPb4 trigonal pyramid. In the third Cl1- site, Cl1- is bonded in a 4-coordinate geometry to three equivalent K1+ and two equivalent Pb2+ atoms. In the fourth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to two equivalent K1+ and three Pb2+ atoms. In the fifth Cl1- site, Cl1- is bonded in a 4-coordinate geometry to two equivalent K1+ and three Pb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Tuning Phonon Energies in Lanthanide-doped Potassium Lead Halide Nanocrystals for Enhanced Nonlinearity and Upconversion

Optical applications of lanthanide-doped nanoparticles require materials with low phonon energies to minimize nonradiative relaxation and promote nonlinear processes like upconversion. Heavy halide hosts offer low phonon energies but are challenging to synthesize as nanocrystals. Here, we demonstrate the size-controlled synthesis of low-phonon-energy KPb 2 X 5 (X=Cl, Br) nanoparticles and the ability to tune nanocrystal phonon energies as low as 128 cm -1 . KPb 2 Cl 5 nanoparticles are moisture resistant and can be efficiently doped with lighter lanthanides. Further, the low phonon energies of KPb 2 X 5 nanoparticles promote upconversion luminescence from higher lanthanide excited states and enable highly nonlinear, avalanche-like emission from KPb 2 Cl 5 : Nd 3+ nanoparticles. The realization of nanoparticles with tunable, ultra-low phonon energies facilitates the discovery of nanomaterials with phonon-dependent properties, precisely engineered for applications in nanoscale imaging, sensing, luminescence thermometry and energy conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗