29 Structural Study of the Modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 . . .
461
29.2 Preparation of Modified Ceramics
Macro- and micro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics was obtained via
traditional ceramic technology as was described in greater details elsewhere [4, 12,
16, 20, 22]. Equal molar amounts of initial powders were mixed in a planetary ball
mill for 96 h in an environment with acetone to obtain mixture. The aqueous solution
of polyvinyl alcohol was used for obtaining of the molding powder. Bilateral compression was performed in steel molds. After pressing these samples were sintered
in a furnace at maximal temperature (T s ) 1100 Ñ ´ for 2 h. To validate PAL investigations performed, we divided the Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics into two groups
presumably not affecting lifetime spectra – the Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 -micro- and
Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 -macro-modified ceramics prepared by preliminary sifting
of powder through fine (with 0.1 mm pores) and more rough sieve (0.5 mm pores). In
both cases, the sizes of intrinsic pores are too large to change significantly positron
annihilation spectra [20].
To preparation of Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics, the precise amounts of high
purity and previously tested carbonate salts were weighted and wet mixed. This
mixture was thermally decomposed in the air at 700 ± 5 ◦ C for 4 h [12, 16]. Then
the obtained powders were milled, blended with organic binder, and pressed into
the disks of approximately 10 mm in diameter and 1 mm in thickness. The prepared
four batches of blanks were sintered in the air in respect to the time-temperature
regimes (see Fig. 29.1).
It should be noted the sintering route of ceramics was performed to ensure
all necessary conditions for inhibition effect in degradation [23], the content of
additional NiO phase with NaCl-type structure having decisive role in the final
ceramic structure. In fact, we deal with Ni-deficient ceramics in respect to stoichiometric Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 composition taken as start one in disproportionality
0
200
400
600
800
1000 1200 1400
0
200
400
600
800
1000
1200
1400
No 1 (1 % NiO)
No 2 (8 % NiO)
No 3 (10 % NiO)
No 4 (12 % NiO)
T,
o
C
t, min.
Fig. 29.1 Time-temperature sintering regime for Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics [16]
461
29.2 Preparation of Modified Ceramics
Macro- and micro-modified Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics was obtained via
traditional ceramic technology as was described in greater details elsewhere [4, 12,
16, 20, 22]. Equal molar amounts of initial powders were mixed in a planetary ball
mill for 96 h in an environment with acetone to obtain mixture. The aqueous solution
of polyvinyl alcohol was used for obtaining of the molding powder. Bilateral compression was performed in steel molds. After pressing these samples were sintered
in a furnace at maximal temperature (T s ) 1100 Ñ ´ for 2 h. To validate PAL investigations performed, we divided the Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 ceramics into two groups
presumably not affecting lifetime spectra – the Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 -micro- and
Cu 0.4 Co 0.4 Ni 0.4 Mn 1.8 O 4 -macro-modified ceramics prepared by preliminary sifting
of powder through fine (with 0.1 mm pores) and more rough sieve (0.5 mm pores). In
both cases, the sizes of intrinsic pores are too large to change significantly positron
annihilation spectra [20].
To preparation of Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics, the precise amounts of high
purity and previously tested carbonate salts were weighted and wet mixed. This
mixture was thermally decomposed in the air at 700 ± 5 ◦ C for 4 h [12, 16]. Then
the obtained powders were milled, blended with organic binder, and pressed into
the disks of approximately 10 mm in diameter and 1 mm in thickness. The prepared
four batches of blanks were sintered in the air in respect to the time-temperature
regimes (see Fig. 29.1).
It should be noted the sintering route of ceramics was performed to ensure
all necessary conditions for inhibition effect in degradation [23], the content of
additional NiO phase with NaCl-type structure having decisive role in the final
ceramic structure. In fact, we deal with Ni-deficient ceramics in respect to stoichiometric Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 composition taken as start one in disproportionality
0
200
400
600
800
1000 1200 1400
0
200
400
600
800
1000
1200
1400
No 1 (1 % NiO)
No 2 (8 % NiO)
No 3 (10 % NiO)
No 4 (12 % NiO)
T,
o
C
t, min.
Fig. 29.1 Time-temperature sintering regime for Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics [16]