Process for the preparation of voltage non-linearity type resistors

A voltage non-linearity type resistor and a process for the preparation of a voltage non-linearity type resistor wherein pre-sintering is effected at a temperature of no lower than 700.degree. C. with a basic composition including X mole % of ZnO and (100-X) mole % of Fe.sub.2 O.sub.3 (wherein 40.ltoreq.X.ltoreq.60), and sintering is then effected with the resulting pre-sintered body to which at least one of V.sub.2 O.sub.5, Bi.sub.2 O.sub.3, MgO, Al.sub.2 O.sub.3, MoO.sub.3, Sb.sub.2 O.sub.3, SiO.sub.2, NiO, SrO.sub.2 and PbO is further added in a proportion of 0.01-40% by weight.

FIELD OF THE INVENTION 
The present invention relates to a process for the preparation of voltage 
non-linearity type resistors. 
BACKGROUND OF THE INVENTION 
The voltage-current characteristics of the voltage non-linearity type 
resistor are generally given in terms of the following expression: 
EQU I=(V/C).sup..alpha. 
wherein 
V is a voltage applied on a resistor, 
I is a current flowing through the resistor, 
C is a constant corresponding to a voltage generated when a given current 
is flowing, and 
.alpha. is an index of a non-linearity coefficient. 
The larger the index .alpha., the better the non-linearity will be. 
The voltage non-linearity type resistors used heretofore are based on SiO 
and ZnO. The SiO base resistors are prepared by sintering of SiO particles 
having a grain size of about 100 microns, and their voltage non-linearity 
characteristics are adjustable by varying the number of grain boundaries 
in the flowing direction of current. However, their non-linearity 
coefficient is relatively small and on the order of 3-7. Referring to SiO 
resistors for low-voltage applications, the number of grain boundaries 
should be reduced due to a high C value per one grain boundary. In 
consequence a problem arises wherein a reduction in the number of grain 
boundaries would lead to a drop of voltage resistance. Turning to the ZnO 
base resistors, they are advantageous in that they can be used in a wider 
range of voltage, since they generally have a coefficient of non-linearity 
of as high as 10-50 and a reduced grain size. However, ZnO resistors are 
disadvantageous in that it is difficult to produce the resistors since 
their non-linearity deteriorates with the lapse of time due to the 
chemical unstability of their main component ZnO. Thus, an increase in 
production cost occurs. 
SUMMARY OF THE INVENTION 
A main object of the present invention is therefore to provide improved 
voltage non-linearity type resistors excelling in both characteristics and 
stability. 
According to the present invention, this object is achieved by the 
provision of a process for the preparation of voltage non-linearity type 
resistors, characterized in that pre-sintering is effected at a 
temperature of no lower than 700.degree. C. with a basic composition 
comprising X mole % of ZnO and (100-X) mole % of Fe.sub.2 O.sub.3 (wherein 
40.ltoreq.X.ltoreq.60), and sintering is then effected with the resulting 
pre-sintered body to which at least one of V.sub.2 O.sub.5, Bi.sub.2 
O.sub.3, MgO, Al.sub.2 O.sub.3, MoO.sub.3, Sb.sub.2 O.sub.3, SiO.sub.2, 
NiO, SrO.sub.2 and PbO is further added in a proportion of 0.01-40% by 
weight. 
Further scope of applicability of the present invention will become 
apparent from the detailed description given hereinafter. However, it 
should be understood that the detailed description and specific examples, 
while indicating preferred embodiments of the invention, are given by way 
of illustration only, since various changes and modifications within the 
spirit and scope of the invention will become apparent to those skilled in 
the art from this detailed description.