Nanocomposites and nanomaterials
Impact of subvalent impurities on optical and structural properties of zirconia-based nanomaterials
Korsunska N.1, Polishchuk Yu.1, Vorona I.1, Lavoryk S.1,2, Ponomaryov S.1, Marie O.3, Portier X.4, Melnichuk L.5, Melnichuk O.5, Khomenkova L.1,6

1 V. Lashkaryov Institute of Semiconductor Physics, Prospect Nauki, 45, Kyiv 03028, Ukraine; E-mail: khomen@ukr.net
2 NanoMedTech LLC, 68 Antonovycha Str, Kyiv 03680, Ukraine
3 LCS (UMR CNRS 6506/ENSICAEN/Normandie Université), 6 Boulevard Maréchal Juin, 14050 Caen, France
4CIMAP, Normandie Univ, ENSICAEN, UNICAEN, CEA, CNRS, 6 Boulevard Maréchal Juin, 14050 Caen, France 
5Mykola Gogol State University of Nizhyn, 2 Hrafska str., Nizhyn 16600, Ukraine 
6National University “Kyiv-Mohyla Academy”, 2 Skovorody str., Kyiv 04070, Ukraine

In the present paper we will demonstrate the effect of subvalent impurities on the properties of (co)doped zirconia-based nanomaterials obtained from zirconium oxychloride or nitrate. Specifically, the effect of the type of raw materials on spatial dopant distribution and oxygen vacancies content in (Cu,Y)-codoped ZrO2 prepared by co-precipitation technique was studied. The samples were investigated by means of diffuse and attenuated total reflectance as well as XRD, EPR, Auger spectroscopy and TEM methods. 
It was observed that annealing of the samples at high temperature stimulates structure transformation, variation of oxygen vacancies content in the grains and amount of dispersed CuO at their surface. These changes depend on Cu content being controlled by surface-volume copper redistribution (copper in- and out-diffusion) and transformation of surface entities. At low Cu content, the amount of oxygen vacancies and CuO varies significantly and non-monotonically with temperature rise, while for higher Cu content, they changes slightly. 
In the samples prepared from oxychloride, the chlorine inside ZrO2 grains was detected. This reduces the amount of oxygen vacancies due to Cl action as compensator for Cu charge. Besides, tight Cu-Cl interaction keeps Cu ions inside the grains that affects significantly the formation of CuO at their surface. The latter reduces the catalytic activity of the powders in the CO PROX reaction.