Pressure-sintering, in which the unfired laminated ferrite plane is placed between two flat punches and pressed during firing, reduces lateral firing shrinkage to less than one percent. A decrease in thickness of the laminate produces the required volume shrinkage. Phlogopite is the most suitable contact material investigated

Wentworth, C.

English

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September 1970	 Brief 70-10380 
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be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Contact Material for Pressure-Sintering Ferrites 
The problem: 
The firing of a laminated ferrite plane or wafer 
(which has found use in random access memories) 
causes it to shrink excessively and nonuniformly in 
all directions. A solution to this problem is to employ 
pressure-sintering, a process in which the unfired 
laminate is placed between two flat punches, or plates, 
and pressed during firing. The application of pres-
sure in this way can reduce the lateral firing shrinkage 
to less than one percent, thus providing the desired 
dimensional uniformity. The required volume shrink-
age is obtained by a decrease in thickness of the lami-
nate. In any pressure-sintering operating, use of a 
contact material (between the sample and pressure 
plate) which does not react with or adhere to the 
sample being sintered is essential. When pressure-
sintering thin, flat wafers without the use of a retain-
ing die, the contact material must remain rigid. 
The solution: 
Of various contact materials (e.g., dense MgO, 
graphite, tungsten, molybdenum, stainless steel, and 
common mica) which were investigated, phlogopite
(a variety of mica) was found to be the most suitable 
for pressure-sintering of ferrite. Satisfactory results 
were obtained using phlogopite wafers in the thick-
ness range of 0.0005 to 0.0015 inch. Ferrite planes 
1.5 x 3.5 x 0.008 inch were successfully pressure-
sintered at 1000°C and 4000 psi using these wafers 
as contact material. Under many firing conditions, 
phlogopite does not stick at all to the ferrite; when it 
does stick, it can be easily peeled off or abraded. If 
abrading is required, it should be done after anneal-
ing. No sticking of the phlogopite to the pressure plate 
(tungsten carbide) was experienced. 
Note: 
No additional documentation is available. 
Patent status: 
No patent action is contemplated by NASA. 
Source: C. Wentworth of 
Radio Corporation of America 
under contract to 
Electronics Research Center 
(ERC- 102 13) 
Category 01 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned-rights.
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Contact material for pressure-sintering ferrites

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