Nanocomposites and nanomaterials

Inner-structured analysis of Ni-enriched ceramics
by PALS method
 H. Klym1, A. Ingram2, Yu. Kostiv1, O. Shpotyuk3 
1 Lviv Polytechnic National University, Bandery str., 12, Lviv-79013, Ukraine 
E-mail: halyna.i.klym@lpnu.ua; yura.kostiv@gmail.com   
2 Opole University of Technology, Ozimska str., 75, Opole- 45370, Poland
3 Vlokh Institute of Physical Optics, Dragomanova str., 23, Lviv-79005, Ukraine

In this work inner void structure in the high-reliable transition-metal manganite Ni-enriched (Cu0.1Ni0.8Co0.2Mn1.9O4) ceramics was investigated using positron annihilation lifetime spectroscopy (PALS). 
The PALS measurements were performed with an ORTEC spectrometer using 22Na source placed between two sandwiched ceramic samples. The obtained data were treated with LT computer program, the best results corresponding to three-component fitting procedures.
By accepting two-state positron trapping model [1], for spinel-type ceramic materials the first component of spectra was connected with main spinel structure and the second one – with extended defects located near grain boundaries in the vicinity of additional extracted phases. The intensity I1 corresponds to the amounts of the main spinel phase, I2 intensity – to the amount of addition NiO phase near grain boundaries, I3 intensity – ortho-positronium decaying in nanopores.
The lifetime of the first and second components for Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics is typically for spinel-structured materials and equal  0.37 and 0.20 ns, accordingly [2]. The intensity of the second component is related with amount of addition NiO phase. The size of nanopores calculated from the lifetime of the third component is near 0.3 Å. Influence of NiO on the transformation of free volume in Ni-enriched ceramics were also studied using positron-positronium trapping algorithm.
   
1.	Klym H., Ingram A. Unified model of multichannel positron annihilation in nanoporous magnesium aluminate ceramics // Journal of Physics: Conference Series, 2007, 79(1) p. 012014.
2.	Klym H., Ingram A., et. al. Structural studies of spinel manganite ceramics with positron annihilation lifetime spectroscopy // Journal of Physics: Conference Series, 2011, 289(1), pp.012010.