Searching for better X-ray and γ-ray photodetectors: structure-composition properties of the TlPb2Br5-xIx quaternary system

Developing X-ray and gamma-ray detectors with stable operation at ambient temperature and high energy resolution is an open challenge. Here, we present an approach to search for new detector materials, combining binary photodetector compounds. More specifically, we explore quaternary TlPb2Br5-xIx compositions, relying on materials synergy between TlBr, TlI, and PbI2 photodetectors. We discover a broad solid solution in the TlPb2Br5-'TlPb2I5' section, which can be derived from a new quaternary compound, TlPb2BrI4, by partial substitution of Br by I atoms on the 4c site or by replacement of I by Br atoms on the 16l site. We carry out a thorough crystallographic analysis of the new TlPb2BrI4 compound and prepare a high-quality standardized structure file. We also complete the phase diagram of the TlPb2Br5-'TlPb2I5' section, based on 21 alloys. Furthermore, we synthesize a series of high quality centimeter-sized TlPb2Br5-xIx single crystals (x = 2, 2.5, 3, 3.5, 4, 4.5) by the Bridgman-Stockbarger method and study their structure and properties using a combination of experimental techniques (X-ray diffraction, X-ray photoelectron spectroscopy, and absorption spectroscopy) and theoretical calculations.

Automated summary

The study presents a method to search for new detector materials by combining binary photodetector compounds. A new solid solution was discovered in the TlPb2Br5-xIx compositions and a high-quality standardized structure file was prepared through thorough crystallographic analysis. In addition, the phase diagram of the TlPb2Br5-'TlPb2I5' section was completed based on 21 alloys.