In this study we undertookto examine the possibilities of obtaining magnetic crystalline materials by the crystallization of the Na
2O-Fe
2O
3-NiO-B
2O
3-P
2O
5 glass or glass-ceramics and of forming the melts into desired shapes by the ordinary glass-forming technique. The composition of the melts studied were: 10-20mol% Na
2O, 25-35mol% Fe
2O
3, 10-20mol% NiO, 10-40mol% B
2O
3 and 10-45mol% P
2O
5. The magnetic properties, electrical conductivity and dielectric relaxation were measured in the quenched and crystallized specimens of Na
2O-Fe
2O
3-NiO-B
2O
3-P
2O
5 series. The results obtaind are as follows:
1) The melts of the compositions: 10-20mol% Na
2O, 25-30mol% Fe
2O
3 10-20mol% NiO, 10-40mol% B
2O
3 and 10-45mol% P
2O
5 could be formed into desired shapes during cooling, and some quenched specimen showed magnetization.
2) Magnetization of glass-ceramics increased with the content of Fe
2O
3; the maximum was found at the composition ratio B
2O
3/B
2O
3+P
2O
5≅0.56-0.85. The intensity of magnetization of No. 7 (quenched specimen) reached 25emu/g at the field of 6500 Oe.
3) The existence of crystallites of spinel-type ferrites such as γ-Fe
2O
3 and NiFe
2O
4 was confirmed by chemical analysis, Curie point, X-ray analysis and IR spectra in some quenched specimens containing a high amount of Fe
2O
3 and a relative high amount of NiO.
4) The type of precipitated crystal in No. 14 specimen changed from γ-Fe
2O
3 to α-Fe
2O
3 and then to NiFe
2O
4 as the heat treatment temperature increased.
5) In the d.c. conductivity of the quenched specimens, very high conductivity was observed at the composition containing the γ-Fe
2O
3. An anomalously large dielectric relaxation spectrum was observed in the 20Na
2O⋅25Fe
2O
3⋅10NiO⋅25B
2O
3⋅20P
2O
5 glass-ceramics.
The origin of magnetic properties was related to the formation of a microstructure such as γ-Fe
2O
3, α-Fe
2O
3 and NiFe
2O
4 in the glassy matrix. The formation of a microstructure like this was considered to cause the anomalous behavior of the electrical properties.
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