462
H. Klym et al.
calculations. Four batches of Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics with 1–12% of NiO
phase were prepared owing to different amounts of thermal energy transferred
during the sintering (batch No. 1–1% NiO, batch No. 2–8% NiO, batch No. 3–10%
NiO, batch No. 4–12% NiO). The latter was numerically determined as square value
restricted by temperature-time curve above straight line corresponding to 920 ◦ C,
which is the temperature of monophase Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramic formation
[16, 23].
29.3 Experimental Details
Structures of grains, grain boundaries, and pores for micro- and macro-modified
Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics were studied using LEO 982 microscope [20,
24]. Pore size distribution in the region from 2 to 300 nm was investigated with
Hg-porosimetry (POROSIMETR 4000) [11, 20, 21].
Microstructure of the Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics was probed using electron microscope JSM-6700F, cross sections morphology of the samples being tested
near surface (0–70 μm depth) and chip centers.
PAL measurements for all samples of ceramics were performed using ORTEC
spectrometer at temperature of 20 ◦ C and relative humidity of ∼35% [11, 16–18,
25]. The isotope 22 Na was used as positron source. The two identical samples of
ceramics were placed in the both sides of the source. The PAL spectra were treated
by LT computer program [26]. For each pair of ceramic samples, we used three
measured positron annihilation spectra. The best results were obtained at threecomponent fitting procedure with parameters of each components (τ 1 , I 1 ), (τ 2 , I 2 ),
and (τ 3 , I 3 ) for micro- and macro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics and
two-component component fitting procedure with parameters (τ 1 , I 1 ), (τ 2 , I 2 ). Such
parameters as average positron lifetimes τ av , positron lifetime in defect-free bulk
τ b , and positron trapping rate in defects κ d were calculated using two-state positron
trapping model [26, 27]. The difference (τ 2 − τ b ) can be accepted as a size measure
of extended defects where positrons are trapped, and the τ 2 /τ b ratio represents the
nature of these defects [28].
29.4 Results and Discussion
29.4.1 Micro- and Macro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4
Ceramics
According to our X-ray diffraction investigations, the micro- and macro-modified
Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics are preferentially of single spinel phase with
lattice parameter of a = 8.365 Å [4, 20]. The XRD patterns for the micro- and
macro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics are shown in Figs. 29.2 and 29.3.
H. Klym et al.
calculations. Four batches of Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics with 1–12% of NiO
phase were prepared owing to different amounts of thermal energy transferred
during the sintering (batch No. 1–1% NiO, batch No. 2–8% NiO, batch No. 3–10%
NiO, batch No. 4–12% NiO). The latter was numerically determined as square value
restricted by temperature-time curve above straight line corresponding to 920 ◦ C,
which is the temperature of monophase Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramic formation
[16, 23].
29.3 Experimental Details
Structures of grains, grain boundaries, and pores for micro- and macro-modified
Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics were studied using LEO 982 microscope [20,
24]. Pore size distribution in the region from 2 to 300 nm was investigated with
Hg-porosimetry (POROSIMETR 4000) [11, 20, 21].
Microstructure of the Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics was probed using electron microscope JSM-6700F, cross sections morphology of the samples being tested
near surface (0–70 μm depth) and chip centers.
PAL measurements for all samples of ceramics were performed using ORTEC
spectrometer at temperature of 20 ◦ C and relative humidity of ∼35% [11, 16–18,
25]. The isotope 22 Na was used as positron source. The two identical samples of
ceramics were placed in the both sides of the source. The PAL spectra were treated
by LT computer program [26]. For each pair of ceramic samples, we used three
measured positron annihilation spectra. The best results were obtained at threecomponent fitting procedure with parameters of each components (τ 1 , I 1 ), (τ 2 , I 2 ),
and (τ 3 , I 3 ) for micro- and macro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics and
two-component component fitting procedure with parameters (τ 1 , I 1 ), (τ 2 , I 2 ). Such
parameters as average positron lifetimes τ av , positron lifetime in defect-free bulk
τ b , and positron trapping rate in defects κ d were calculated using two-state positron
trapping model [26, 27]. The difference (τ 2 − τ b ) can be accepted as a size measure
of extended defects where positrons are trapped, and the τ 2 /τ b ratio represents the
nature of these defects [28].
29.4 Results and Discussion
29.4.1 Micro- and Macro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4
Ceramics
According to our X-ray diffraction investigations, the micro- and macro-modified
Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics are preferentially of single spinel phase with
lattice parameter of a = 8.365 Å [4, 20]. The XRD patterns for the micro- and
macro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics are shown in Figs. 29.2 and 29.3.