posted on 2024-03-07, 18:35authored byJavier García-Alonso, Matteo Amati, Ana Cremades, David Maestre
Nickel manganite (NiMn2O4) samples synthesized
by a vapor–solid method at temperatures in the range of 1000–1400
°C are studied in this work. The stability and properties of
this ternary compound together with the presence of NiO in the form
of p–n heterostructures have been analyzed by means of diverse
electron microscopy and spectroscopy techniques. The formation of
the ternary compound with improved crystallinity is promoted as the
temperature of the synthesis is increased. Moreover, the samples synthesized
at higher temperatures exhibit the growth of microcrystals with micro-
and nanoislands on top of their lateral surfaces, leading to patterned
surfaces with variable Ni and Mn composition. The combination of Raman
spectroscopy, including wavenumber-filtered images, and electron backscattered
diffraction confirms that most of these micro- and nanoislands consist
of NiMn2O4 grown on top of NiO surfaces. X-Ray
photoelectron spectroscopy and microscopy at synchrotron facilities
confirm the presence of nickel manganite nanoislands covering the
surface of NiO surfaces. Aspects such as the growth mechanisms, nickel
manganite vibrational modes, and inversion factor of NiMn2O4 have been discussed in this work.