Structural, EPR and Optical Studies on Cu-doped ZnO Nanoparticles Synthesized by the Sol-Gel Method at Different Calcination Temperatures

  • Roman Buchheit Materials Science Department, Technische Universität Darmstadt, Germany
  • F. Acosta-Humánez Department of Physics, Applied Physics Group, Universidad Nacional de Colombia-Sede Bogot´á, Colombia
  • O. Almanza Department of Physics, Applied Physics Group, Universidad Nacional de Colombia-Sede Bogot´á, Colombia

Abstract

In this work, pure ZnO and Cu-doped ZnO nanoparticles (Zn1-xCuxO, x = 3 at.%) were synthesized using the sol-gel method at three different calcination temperatures (TC = 773 K, 823 K and 873 K.). The particles were analyzed by atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), electron paramagnetic resonance (EPR) at different measurement temperatures and diffuse reflection spectroscopy (DRS). All samples have wurtzite structure and the formation of a CuO was observed as additional phase. The Cu-doped nanoparticles have smaller size than the
pure ZnO particles. EPR analysis shows that in samples of ZnO there is presence of superficial defects (g = 2.036, g = 1.967 and g = 1.958) in increased amount than in doped samples. Both samples shows Zn vacancy with g = 2.004. The Cu EPR signal was simulated by an anisotropic Spin-Hamiltonian with the values of gt = 2.082 and gp = 2.320 and indicating that the Cu2+ ions in the sample have a local configuration with axial symmetry. Cu doped samples reveal a smaller band gap for the Cu-containing samples than for pure ZnO samples. Additionally, the gap of the Cu-containing samples decreases with increasing calcination temperature. Samples calcinated at 823 K are anti-ferromagnetic or ferrimagnetic at temperature lower than TN = 139 K while samples calcinated at 873 K suffer a transition from paramagnetism to ferromagnetism which is characterized by a Curie temperature of
OC = 137 K.

Published
Jul 14, 2016
How to Cite
BUCHHEIT, Roman; ACOSTA-HUMÁNEZ, F.; ALMANZA, O.. Structural, EPR and Optical Studies on Cu-doped ZnO Nanoparticles Synthesized by the Sol-Gel Method at Different Calcination Temperatures. Revista Cubana de Física, [S.l.], v. 33, n. 1, p. 4-11, july 2016. ISSN 2224-7939. Available at: <http://revistacubanadefisica.org/index.php/rcf/article/view/7>. Date accessed: 18 june 2019.
Section
Original Articles