Structural properties and thermal stability of cobalt- and chromium-doped $α-MnO_2$ nanorodsCerc Korošec, Romana (Avtor) Umek, Polona (Avtor) Gloter, Alexandre (Avtor) Padežnik Gomilšek, Jana (Avtor) Bukovec, Peter (Avtor) $α-MnO_2$manganese dioxidedopingEXAFSnanorodsXANES$α-MnO_2$ nanorods were synthesized via the hydrothermal decomposition of $KMnO_4$ in an acidic environment in the presence of $Co^{2+}$ and $Cr^{3+}$ ions. Reactions were carried out at three different temperatures: 90, 130 and 170 °C. All prepared samples exhibit a tetragonal $MnO_2$ crystalline phase. SEM–EDS analysis shows that cobalt cations are incorporated to a higher degree into the $MnO_2$ framework than chromium ions, and that the content of the dopant ions decreases with increasing reaction temperature. The oxidation of $Co^{2+}$ to $Co^{3+}$ during the reaction was proved by an XANES study, while EXAFS results confirm that both dopant ions substitute $Mn^{4+}$ in the center of an octahedron. The K/Mn ratio in the doped samples synthesized at 170 °C is significantly lower than in the undoped samples. Analysis of an individual cobalt-doped $α-MnO_2$ nanorod with HAADF-STEM reveals that the distribution of cobalt through the cross-section of the nanorod is uniform. The course of thermal decomposition of the doped nanorods is similar to that of the undoped ones. Dopant ions do not preserve the $MnO_2$ phase at higher temperatures nor do they destabilize the cryptomelane structure.20172017-08-10 08:40:28Znanstveno delo67303ISSN: 2190-4286UDK: 546.711-31:620.3OceCobissID: 25644839COBISS_ID: 1537419971DOI: 10.3762/bjnano.8.104ISSN pri članku: 2190-4286NUK URN: URN:SI:UM:DK:1M6PJSNJsl