Method for preparing spherical ferrite beads and use thereof
- Oak Ridge, TN
- Knoxville, TN
The invention allows the fabrication of small, dense, highly polished spherical beads of hexagonal ferrites with selected compositions for use in nonreciprocal microwave and mm-wave devices as well as in microwave absorbent or reflective coatings, composites, and the like. A porous, generally spherical bead of hydrous iron oxide is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead is washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) under conditions of elevated temperature and pressure to convert the bead into a mixed hydrous iron-alkaline earth oxide while retaining the generally spherical shape. This mixed oxide bead is then washed, dried, and calcined to produce the desired (BaFe.sub.12 O.sub.19 or SrFe.sub.12 O.sub.19) crystal structure. The calcined bead is then sintered to form a dense bead of the BaFe.sub.12 O.sub.19 and SrFe.sub.12 O.sub.19 phase suitable for polishing and incorporation into various microwave devices and components.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- AC05-96OR22464
- Assignee:
- UT-Battelle, LLC (Oak Ridge, TN)
- Patent Number(s):
- US 6492016
- OSTI ID:
- 874932
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
preparing
spherical
ferrite
beads
allows
fabrication
dense
highly
polished
hexagonal
ferrites
selected
compositions
nonreciprocal
microwave
mm-wave
devices
absorbent
reflective
coatings
composites
porous
bead
hydrous
iron
oxide
sol-gel
process
form
substantially
rigid
fine
crystallite
size
correspondingly
finely
distributed
internal
porosity
resulting
washed
hydrothermally
reacted
soluble
alkaline
earth
salt
typically
sr
conditions
elevated
temperature
pressure
convert
mixed
iron-alkaline
retaining
shape
dried
calcined
produce
bafesub12
osub19
srfesub12
crystal
structure
sintered
phase
polishing
incorporation
components
elevated temperature
alkaline earth
iron oxide
wave device
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