Hydrothermal synthesis of Metal tellurates nanocrystals (Ni 3 TeO 6 and Cu 3 TeO 6 ) with magnetic and photoconductivity properties Javier Fernandez Catala 1,2 , Harishchandra Singh 1 , Shubo Wang 1 , Hannu Huhtinen 3 , Petriina Paturi 3 , Yang Bai 4 , Wei Cao 2 1 Nano and Molecular Systems Research Unit, University of Oulu, FIN-90014, Finland. 2 Materials Institute and Inorganic Chemistry Department, University of Alicante, Ap. 99, E-03080 Alicante, Spain. 3 Wihuri Physical Laboratory, Department of Physics and Astronomy, FIN-20014 University of Turku, Finland. 4 Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, FI-90570 Oulu, Finland. by 3d transition metal (M), such as Ni, Cu, Co …, tellurium (Te) and oxygen (O) 2,3 .The main synthetic processes used for these materials is solid state synthesis, which does not allow an exhaustive control of its morphology and particle size 4 . So, the design of novel synthetic strategies of MTOs, with magnetic and optical properties, using additives (NaOH) and novel procedures (hydrothermal synthesis) is crucial to open the door to this material for different applications 4 .In this work, a hydrothermal synthesis methodology is proposed to synthesize two metal tellurate M 3 TeO 6 (M= Ni or Cu), using NaOH as an additive. The hydrothermal methodology favors the synthesis of MTO without the incorporation of Na in the metal tellurate crystal structure (Na 2 M 2 TeO 6 ). Synchrotron and lab source X-ray diffraction are used to probe different crystalline phases. TEM and SEM analyses show that Ni 3 TeO 6 and Cu 3 TeO 6 are composed by particles with a size of 37 and 140 nm, respectively. STEM-EDS show that the Na was not incorporated in the structure of the material. UV-Vis spectroscopy shows that Ni 3 TeO 6 and Cu 3 TeO 6 present semiconductor properties.The as-prepared Ni 3 TeO 6 and Cu 3 TeO 6 present magnetic properties, with T N of 57 and 68 K, respectively, showing comparable magnetic properties to the metal tellurates obtained by solid state method. Interestingly, NTO and CTO not only show semiconducting nature but also photoconductivity. Proposed design scheme opens the door to any metal tellurates for controllable synthesis towards different applications. Authors thank European Union-Next Generation EU, MINECO, and University of Alicante for a postdoctoral research grant (MARSALAS21-09), Jenny and Antti Wihuri Foundation, ERC (European Research Council) Starting Grant project UNIFY (grant agreement number 101039110), and Consolidator Grant CATCH (grant agreement no. 101002219). Thank Dr. Graham King for synchrotron XRD data and Center of Materials Analysis (CMA) (University of Oulu) for characterizations. Part of the research described in this work was performed at the Canadian Light Source, which is supported by the Canada Foundation for Innovation (CFI), the Natural Sciences and Engineering Research Council (NSERC), the National Research Council (NRC), the Canadian Institutes of Health Research (CIHR), the Government of Saskatchewan, and the University of Saskatchewan. References 1. Cheong, S. W. et al.Nat. Mater.2007,6,13–20 2. Xu, L. et al.Mater. Lett.2016,184,1–4. 3. Mutharani, B.et al. Microchem. J.2020,159,105378. 4. Fernandez-Catala J. et al. ACS Appl. Nano Mat. 2023, 6, 4887–4897 The design and synthesis of materials with multiferroic properties has been attracting the attention of the scientific community 1 . One promising class of multiferroics materials is metal tellurates M 3 TeO 6 (MTO), which are composed
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