468
H. Klym et al.
access to the environment to be determined. On the other hand, PAL spectroscopy
can probe both open and closed pores in functional oxide ceramics of sizes ranging
from atomic scale to several tens of nanometers.
29.4.2 Technologically Modified Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4
Ceramics
In respect to the results of microstructure characterization with X-ray diffractometry
method, the lattice constant of the main spinel was slightly grown from 8.38 ÇÑ
8.41 Å without significant changes in the parameter of additional NiO phase (at the
level of 4.17–4.19 Å) despite increase in the content of this phase from 1 to 12%
[16].
To explain the above phenomena, microstructure of the prepared ceramics
was studied. As it follows from Fig. 29.6, the prepared ceramic samples differ
significantly by their grain-pore microstructure.
The samples of batch No. 1 (Fig. 29.6a) are characterized by fine 1–3 μm grains.
The numerous intergranular pores are small enough in these samples, their sizes not
exceeding 1–2 μm. White film, which can be attributed to additional NiO phase
extractions, weakly appears in these ceramics mainly near intergrain boundaries;
sometimes it partially fills of pores. The samples of batch No. 2 (Fig. 29.6a) are
characterized by larger grains with sizes near 5–7 μm, some of them achieving
10 μm. The white NiO film appears in these ceramics only in the regions of
grain boundaries. The grain structure of the samples of batch No. 3 (Fig. 29.6c)
gradually changes. The corresponding chip structure of these ceramics is more
monolithic, it being characterized only by separate pores with 1–3 μm in sizes.
White NiO film appears as bright layer of 10 μm thickness on the grain surface
of these samples. In contrast, the grain structure of the samples of batch No. 4
(Fig. 29.6d) attains fully monolithic shape. Only some individual pores of relatively
large sizes (near 3–5 μm) are observed in these ceramics, the NiO appearing as
uniform layer on the whole ceramic surface. The observed additional NiO phase
is nonuniformly distributed within ceramic bulk, being more clearly pronounced
near grain boundaries. These phase extractions serve as specific trapping centers for
positrons penetrating ceramics.
Investigation of element composition of grain for Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4
ceramics specifies on their stoichiometry (Fig. 29.7). However basic influence on
the structural processes in material open and closed pores formed by modification
on the stage of sintering is realized.
By accepting two-state positron trapping model [27, 28], 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 I 1 corresponds to the amounts
H. Klym et al.
access to the environment to be determined. On the other hand, PAL spectroscopy
can probe both open and closed pores in functional oxide ceramics of sizes ranging
from atomic scale to several tens of nanometers.
29.4.2 Technologically Modified Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4
Ceramics
In respect to the results of microstructure characterization with X-ray diffractometry
method, the lattice constant of the main spinel was slightly grown from 8.38 ÇÑ
8.41 Å without significant changes in the parameter of additional NiO phase (at the
level of 4.17–4.19 Å) despite increase in the content of this phase from 1 to 12%
[16].
To explain the above phenomena, microstructure of the prepared ceramics
was studied. As it follows from Fig. 29.6, the prepared ceramic samples differ
significantly by their grain-pore microstructure.
The samples of batch No. 1 (Fig. 29.6a) are characterized by fine 1–3 μm grains.
The numerous intergranular pores are small enough in these samples, their sizes not
exceeding 1–2 μm. White film, which can be attributed to additional NiO phase
extractions, weakly appears in these ceramics mainly near intergrain boundaries;
sometimes it partially fills of pores. The samples of batch No. 2 (Fig. 29.6a) are
characterized by larger grains with sizes near 5–7 μm, some of them achieving
10 μm. The white NiO film appears in these ceramics only in the regions of
grain boundaries. The grain structure of the samples of batch No. 3 (Fig. 29.6c)
gradually changes. The corresponding chip structure of these ceramics is more
monolithic, it being characterized only by separate pores with 1–3 μm in sizes.
White NiO film appears as bright layer of 10 μm thickness on the grain surface
of these samples. In contrast, the grain structure of the samples of batch No. 4
(Fig. 29.6d) attains fully monolithic shape. Only some individual pores of relatively
large sizes (near 3–5 μm) are observed in these ceramics, the NiO appearing as
uniform layer on the whole ceramic surface. The observed additional NiO phase
is nonuniformly distributed within ceramic bulk, being more clearly pronounced
near grain boundaries. These phase extractions serve as specific trapping centers for
positrons penetrating ceramics.
Investigation of element composition of grain for Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4
ceramics specifies on their stoichiometry (Fig. 29.7). However basic influence on
the structural processes in material open and closed pores formed by modification
on the stage of sintering is realized.
By accepting two-state positron trapping model [27, 28], 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 I 1 corresponds to the amounts