Nanocrystalline CaWO4 and ZnWO4 Tungstates for Hybrid Organic–Inorganic X-ray Detectors

The experiment at the DESY PETRA-III synchrotron was performed within project No. I-20211105 EC at the Institute of Solid State Physics, University of Latvia, as the Cen ter of Excellence has received funding from the European Union’s Horizon 2020 Framework Pro gramme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.Hybrid materials combining an organic matrix and high-Z nanomaterials show potential for applications in radiation detection, allowing unprecedented device architectures and functionality. Herein, novel hybrid organic–inorganic systems were produced using a mixture of tungstate (CaWO4 or ZnWO4) nanoparticles with a P3HT:PCBM blend. The nano-tungstates with a crystallite size of 43 nm for CaWO4 and 30 nm for ZnWO4 were synthesized by the hydrothermal method. Their structure and morphology were characterized by X-ray diffraction and scanning electron microscopy. The hybrid systems were used to fabricate direct conversion X-ray detectors able to operate with zero bias voltage. The detector performance was tested in a wide energy range using monochromatic synchrotron radiation. The addition of nanoparticles with high-Z elements improved the detector response to X-ray radiation compared with that of a pure organic P3HT:PCBM bulk heterojunction cell. The high dynamic range of our detector allows for recording X-ray absorption spectra, including the fine X-ray absorption structure located beyond the absorption edge. The obtained results suggest that nanocrystalline tungstates are promising candidates for application in direct organic–inorganic X-ray detectors.--//-- This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Latvian Council of Science project No. lzp-2019/1-0071; Institute of Solid State Physics, University of Latvia received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Impact of the local structure on the thermochromic properties of copper molybdate and its solid solutions

Elektroniskā versija nesatur pielikumusMateriālu funkcionālās īpašības ir cieši saistītas ar to struktūru un ķīmisko sastāvu. Darbā tiek pētīta saikne starp vara molibdāta (CuMoO4) un tā cieto šķīdumu ar volframu un cinku (CuMo1-xWxO4 un Cu1-xZnxMoO4) lokālo atomāro struktūru un termohromajām īpašībām, izmantojot rentgenstaru absorbcijas un rezonanses rentgenstaru emisijas spektroskopijas (XAS un RXES) metodes. Eksperimentālie dati tiek interpretēti, balstoties uz apgrieztās Monte-Karlo metodes modelēšanu un teorētiskiem aprēķiniem. Darbā tiek nodemonstrēts, ka XAS un RXES metodes ir labi piemērotas lokālas struktūras pētījumiem materiālos ar zemu simetriju, kā arī tiek izskaidrota apskatīto materiālu lokālās struktūras izkropļojumu un režģa dinamikas saistība ar to termohromajām īpašībām. Atslēgas vārdi: CuMoO4, rentgenabsorbcijas spektroskopija, EXAFS, XANES, apgrieztā Monte-Karlo metodeThe functional properties of materials are closely related to their structure and composition. In this thesis, the relationship between the local atomic structure and thermochromic properties of copper molybdate (CuMoO4) and its solid solutions with tungsten and zinc (CuMo1-xWxO4 and Cu1-xZnxMoO4) is studied using X-ray absorption and resonant X-ray emission spectroscopy (XAS and RXES). Experimental data are interpreted based on reverse Monte Carlo modeling and theoretical calculations. The study demonstrates the possibilities of the XAS and RXES methods to probe the local structure changes in materials with low symmetry, as well as explains the relationship between the local structure distortions and lattice dynamics of the considered materials and their thermochromic properties. Keywords: CuMoO4, X-ray absorption spectroscopy, EXAFS, XANES, reverse Monte Carlo metho