Synthesis of nanosized zinc and magnesium chromites starting from PVA–metal nitrate solutions Marcela Stoia • Mirela Barbu • Mircea S ¸ tefa ˘nescu • Paul Barvinschi • Lucian Barbu-Tudoran CEEC-TAC1 Conference Special Issue Ó Akade ´miai Kiado ´, Budapest, Hungary 2011 Abstract In this article, we present a detailed study regarding the preparation of nanosized zinc and magnesium chromites starting from a 4% poly(vinyl)alcohol (PVA) aqueous solution and metal nitrates. The controlled thermal treatment of these solutions has permitted the isolation of an intermediary solid product, used as precursor of the preferred mixed oxides: zinc and magnesium chromites. The as- obtained precursors were characterized by FT-IR spectrom- etry and thermal analysis. FT-IR spectrometry has evidenced the disappearance of the NO 3 - anions at 140 °C, due to the redox interaction with PVA. The thermal decompositions of the synthesized precursors were different, as resulted from both thermal analysis and FT-IR spectrometry. Thus, while ZnCrPVA precursor decomposes up to 400 °C with formation of zinc chromite, the precursor MgCrPVA decomposes up to 500 °C, with formation of MgCrO 4 as intermediary amor- phous phase. By thermal decomposition of MgCrO 4 at 500 °C, weakly crystallized MgCr 2 O 4 powder is obtained. The obtained chromite powders consist of fine nanoparticles with diameters ranging from 10 to 30 nm at 500 °C; on raising the annealing temperature to 1000 °C, chromite particles become octahedral, with diameter up to 500 nm, but with no sign of sintering. Keywords Polyvinyl alcohol Á Chromites Á Thermal decomposition Á Precursor Á FT-IR Abbreviations PVA Polyvinyl alcohol FT-IR Fourier transformed infrared spectroscopy XRD X-ray diffractometry SEM Scanning electron microscopy Introduction The synthesis of metal chromites with spinel structures is a subject that acquired keen researcher interest from early times because of their technological applications [1]. In the last decade, the synthesis of tailored ultrafine microstruc- ture allowed the obtaining of solids with new electronic/ atomic structure. These fine ceramic materials ( \ 100 nm) have reached high technological levels in various fields of applications because of their properties (high elastic mod- ulus, high hardness, general refractoriness, and low relative density) being much improved over those of conventional ceramics ( [ 10 lm). Thus, the synthesis of fine ceramic powders with uniform composition is desirable in the improvement of existing ceramics [2]. Various chemical methods were developed for the syn- thesis of pure, single-phase, mixed oxide powders with controlled powder characteristics. Some of these chemical routes even have a tendency to result in other phases, along with the preferred mixed oxide. Polyvinyl alcohol (PVA) has been in use since 1999 for the synthesis of several mixed oxides, either by polymerization and burning of the as-resulted gel [3, 4], or by evaporation from solutions [5], M. Stoia (&) Á M. Barbu Á M. S ¸ tefa ˘nescu University ‘‘Politehnica’’ Timisoara, Piata Victoriei no. 2, 300006 Timisoara, Romania e-mail: marcela.stoia@chim.upt.ro P. Barvinschi West University of Timisoara, Bv. V. Parvan no. 4, 300223 Timisoara, Romania L. Barbu-Tudoran Babes-Bolyai University, 5-7 Clinicilor Street, 400006 Cluj-Napoca, Romania 123 J Therm Anal Calorim (2012) 110:85–92 DOI 10.1007/s10973-011-2084-6