in case an amount of specific additives which are to be added to a ceramic - material composition containing batio 3 as a substrate is fixed , e . g ., when the additive amounts of sio 2 and mn or mn ion are sio 2 = 0 . 1 % by weight and mn = 0 . 020 % by weight in a positive temperature coefficient thermistor which has ( bapbcay ) tio 3 + sio 2 + mn , it is seen a sudden standing - up of temperature - resistance characteristic after the curie point ( tc ) as shown in fig1 . namely , according to fig2 when the thermistor element generates heat after the tc , the current value is suddenly decreased in inverted proportion to the voltage value even though the applied voltage is increased and thus , it can be considered that the increase of electric power is suppressed . when the voltage - current characteristic thereof is seen , it has been found that a damping characteristic is very close to a linear line of 45 ° at the region of at least 100 v to 240 v of applied voltage , as shown in fig2 . namely , it has been found that damping characteristic which satisfies the relationship of in cartesian coordinates having both logarithmic scales of an abscissa axis vx and ordinate axis iy . in other words , since consumption of electric power is constant in the specific range of the voltage , the thermistor element is heated at a constant temperature . in fig1 characteristics of the conventional thermistor element containing a ceramic material composition having batio 3 used as a substrate are shown as a comparative example . in view of fig2 when a ceramic composition in which the additive amount of sio 2 of ( bapbcay ) tio 3 + sio 2 + mn or mn ion is 0 . 1 % by weight and that of mn or mn ion is 0 . 020 % by weight is sintered to produce a positive thermistor element and this element is used as an exothermic device , change in consumed electric power p = vi is small at the applied voltage between 100 v and 240 v . thus , there causes almost no difference of the exothermic temperature at least within the range of from 100 v to 240 v of applied voltage . in general , in a normal positive temperature coefficient thermistor , as shown in the comparative example in fig2 the damping characteristic is generally lower than the linear line of 45 °, and as a result , the greater the applied voltage is , the more the consumed electric power increases and the higher the exothermic temperature becomes . this specific characteristics according to the present invention have been obtained from the results of the experiments . according to the abovedescribed composite , the range in which 45 ° linear line characteristic is shown is about from 70 ° c . to 250 ° c . conventionally , this range includes the range of 100 v to 240 v of the commercial electric source - voltage . the other feature of the above - described composition is to obtain high dielectric strength . moreover , the exothermic temperature can be arbitrarily controlled by increasing or decreasing the amount of pb in the composition . on the other hand , in a composition of ( ba , pb , ca , y ) tio 3 + sio 2 ( 0 . 1 % by weight )+ mn ( 0 . 020 % by weight ), it is recognized that similar damping characteristic is obtained in voltage - current characteristic even though a composition in which ca is replaced with sr is used . as shown in the comparative example of fig3 an exothermic temperature generally changes in inverted proportion to a normal temperature - resistance r 25 . however , in the present invention as shown in fig3 even in a case of the composition in which ca is replaced with sr , there is almost no change of exothermic temperature within the range of the normal temperature - resistance r 25 which can be normally used . this means that when more than two sets of the positive temperature coefficient thermistors according to the composition of the present invention are used as an exothermic device , even though the normal temperature - resistances r 25 of the respective thermistors are not the same , the same exothermic amount can be obtained . accordingly , the positive temperature coefficient thermistor according to the present invention can be made with a shape of cylinder or segment and electrodes can be fitted to both faces of the thermistor . table 2 shows the result of normal temperature - resistance ( kω ) exotherm temperatures (° c .) of applied voltages 220 v and 100 v , dielectric strength ( v ) and curie point (° c .) measured with respect to positive temperature coefficient thermistors sintered by fixing x = 7 . 0 mol . % and changing y , z and α , β in a ceramic composite of ( ba 1 - x - y - z pb x ca y y z ) ti 1 . 000 o 3 + α wt % sio 2 + β wt % mn . table 2__________________________________________________________________________i ( ba . sub . 1 - x - y - z pb . sub . x ca . sub . y y . sub . z ) ti . sub . 1 . 000 o . sub . 3 + αwt % sio . sub . 2 + β wt % mnpb ca y normal exotherm temperature di - egree . c . )( mol ( mol ( mol sio . sub . 2 mn temper - difference electric curier %) %) %) ( wt %) ( wt %) sintering ature of strength pointx y z α β pattern resistance 100 v 220 v temperature ( v ) (° c . ) __________________________________________________________________________hx - 147 . 0 2 . 0 0 . 37 0 . 1 0 . 020 1330 ° c . × 1 hr 1 . 61 - 2 . 24 161 . 8 - 161 . 9 166 . 6 - 167 . 3 4 . 8 - 5 . 4 780 vhx - 15 &# 34 ; &# 34 ; 0 . 40 &# 34 ; &# 34 ; &# 34 ; 1 . 45 - 2 . 26 160 . 5 - 161 . 8 163 . 8 - 165 . 7 3 . 3 - 3 . 9hx - 16 &# 34 ; &# 34 ; 0 . 43 &# 34 ; &# 34 ; &# 34 ; 0 . 63 - 1 . 00 161 . 4 - 161 . 7 165 . 3 - 168 . 3 4 . 6 - 4 . 9hx - 17 &# 34 ; 4 . 0 0 . 37 &# 34 ; &# 34 ; &# 34 ; 2 . 03 - 2 . 35 159 . 5 - 159 . 9 162 . 0 - 162 . 6 2 . 5 - 2 . 7hx - 18a &# 34 ; &# 34 ; 0 . 40 &# 34 ; &# 34 ; &# 34 ; 1 . 94 - 2 . 77 160 . 2 - 160 . 7 162 . 0 - 162 . 7 1 . 8 - 2 . 1 1300 151hx - 18b &# 34 ; &# 34 ; &# 34 ; &# 34 ; &# 34 ; &# 34 ; 1 . 37 - 1 . 78 160 . 2 - 161 . 4 162 . 6 - 163 . 3 1 . 9 - 2 . 6hx - 19 &# 34 ; &# 34 ; 0 . 43 &# 34 ; &# 34 ; &# 34 ; 0 . 76 - 1 . 18 159 . 7 - 160 . 0 163 . 0 - 163 . 9 3 . 0 - 4 . 0hx - 40 &# 34 ; 5 . 0 0 . 40 &# 34 ; &# 34 ; &# 34 ; 2 . 77 - 4 . 05 157 . 0 - 158 . 7 160 . 4 - 160 . 9 1 . 9 - 3 . 4hx - 41 &# 34 ; 6 . 0 &# 34 ; &# 34 ; &# 34 ; &# 34 ; 1 . 21 - 1 . 48 157 . 3 - 159 . 8 159 . 7 - 162 . 3 2 . 4 - 2 . 8hx - 42 &# 34 ; 4 . 0 0 . 42 0 . 2 &# 34 ; &# 34 ; 0 . 44 - 0 . 70 181 . 5 - 163 . 8 166 . 6 - 169 . 6 5 . 1 - 5 . 8hx - 43 &# 34 ; &# 34 ; &# 34 ; &# 34 ; 0 . 021 &# 34 ; 0 . 86 - 1 . 03 159 . 6 - 162 . 2 163 . 6 - 166 . 0 3 . 8 - 4 . 3hx - 44 &# 34 ; 6 . 0 0 . 40 0 . 2 0 . 020 &# 34 ; 0 . 52 - 0 . 92 160 . 0 - 162 . 2 164 . 0 - 167 . 0 4 . 0 - 5 . 3hx - 45 &# 34 ; &# 34 ; &# 34 ; &# 34 ; 0 . 021 &# 34 ; 0 . 89 - 1 . 17 160 . 0 - 161 . 2 164 . 2 - 165 . 8 4 . 1 - 4 . 6__________________________________________________________________________ specimens hx12 , hx13 , hx24 , hx25 , hx26 , hx28 to hx32 were not used for th experiment since they were destroyed in their forms of their electrodes were separated at the time when they were molded into a pattern of an arcshaped segment or at the sintering time . specimens hx18a and hx18b are experimental data in cases that normal temperature resistance were differentiated . from the result of table 2 , when it was preset that the additive amount of sio 2 is α = 0 . 1 % by weight and the additive amount of mn or mn ion is β = 0 . 020 % by weight , the temperature difference of exothermic temperature between at the applied voltage of 220 v and 100 v is greatly reduced to less than 7 ° c . when either one of the amount of α and β is increased even slightly , the temperature difference of the exothermic temperatures is also lower than 7 ° c ., but there is a tendecy of increase in the temperature difference . although the measured values are not constant , when the values of dielecric strength and normal temperature resistance are judged in total , it can be said that specimen hx - 18a , i . e ., thermistor sintered by presetting substantially α = 0 . 1 % by weight , β = 0 . 020 % by weight , x = 7 . 0 % by weight , y = 4 . 0 % by weight and z = 0 . 40 % by weight , is excellent in voltage - current damping characteristic . thus , these compositions can be used in the invention . table 3 shows measured results in case that the additive amount of sio 2 is fixed to 0 . 4 % by weight and the additive amounts of other ingredients are varied . as apparent from table 3 , the temperature difference between exothermic temperatures at 220 v and 100 v of applied voltage , is remarkably increased in comparison with table 2 . thus , these compositions can not be used in the invention . table 3__________________________________________________________________________ ( ba . sub . 1 - x - y - z pb . sub . x ca . sub . y y . sub . z ) ti . sub . 1 . 002 o . sub . 3 + 0 . 4 wt % sio . sub . 2 + β wt % mnpb ca y narmal exotherm temperature (° c . )( mol mn ( mol ( mol tempera - difference dielectric curier %) ( wt %) %) %) sintering ture of strength pointx β y z pattern resistance 100 v 220 v temperature ( v ) (° c . ) __________________________________________________________________________hx - 10a 10 . 5 0 . 022 16 . 0 0 . 40 1320 ° c . × 1 hr 2 . 44 - 2 . 95 154 . 9 - 155 . 7 164 . 4 - 165 . 5 9 . 8 - 10 . 7 155 10b &# 34 ; &# 34 ; &# 34 ; 0 . 37 &# 34 ; 1 . 53 - 2 . 04 157 . 7 - 158 . 7 167 . 0 - 167 . 7 8 . 9 - 9 . 3 10c &# 34 ; &# 34 ; &# 34 ; 0 . 34 1330 ° c . × 2 hr 2 . 46 - 3 . 65 158 . 5 - 160 . 8 166 . 8 - 169 . 1 8 . 3 - 8 . 9 10d &# 34 ; &# 34 ; &# 34 ; 0 . 31 &# 34 ; 1 . 06 - 1 . 22 165 . 7 - 166 . 1 174 . 1 - 174 . 5 8 . 4 - 8 . 6hx - 1 12 . 0 0 . 022 13 . 5 0 . 54 1330 ° c . × 1 hr 14 . 6 - 19 . 9 150 . 5 - 152 . 8 167 . 7 - 169 . 2 15 . 3 - 17 . 2 2 &# 34 ; &# 34 ; &# 34 ; 0 . 50 &# 34 ; 1 . 75 - 2 . 00 166 . 9 - 168 . 5 172 . 9 - 174 . 5 5 . 7 - 6 . 4 138 3 &# 34 ; &# 34 ; &# 34 ; 0 . 46 1320 ° c . × 1 hr 3 . 48 - 4 . 87 160 . 1 - 162 . 1 172 . 0 - 173 . 0 10 . 9 - 12 . 2 3a 10 . 5 &# 34 ; &# 34 ; 0 . 43 1330 ° c . × 2 hr 2 . 11 - 3 . 60 160 . 1 - 162 . 1 168 . 5 - 170 . 3 8 . 2 - 8 . 4 3b &# 34 ; &# 34 ; &# 34 ; 0 . 40 &# 34 ; 0 . 83 - 1 . 50 166 . 4 - 167 . 6 173 . 5 - 175 . 5 7 . 1 - 7 . 9 3c &# 34 ; &# 34 ; &# 34 ; 0 . 37 &# 34 ; 0 . 63 - 1 . 22 168 . 3 - 169 . 2 175 . 7 - 176 . 8 7 . 4 - 7 . 6 3d &# 34 ; &# 34 ; &# 34 ; 0 . 34 &# 34 ; 0 . 98 - 1 . 47 167 . 4 - 168 . 9 175 . 3 - 175 . 8 7 . 6 - 8 . 2hx - 4 11 . 0 0 . 022 10 . 0 0 . 46 1310 ° c . × 1 hr 1 . 29 - 1 . 94 167 . 3 - 168 . 9 176 . 4 - 177 . 3 8 . 4 - 9 . 1 5 &# 34 ; &# 34 ; &# 34 ; 0 . 47 &# 34 ; 1 . 22 - 1 . 86 168 . 9 - 170 . 5 176 . 4 - 177 . 0 6 . 3 - 7 . 5hx - 6 11 . 0 0 . 022 6 . 0 0 . 46 1320 ° c . × 1 hr 0 . 41 - 0 . 47 179 . 4 - 179 . 6 187 . 2 - 187 . 9 7 . 8 - 8 . 5 7 &# 34 ; &# 34 ; &# 34 ; 0 . 48 &# 34 ; 0 . 68 - 0 . 78 176 . 9 - 177 . 6 184 . 0 - 184 . 8 7 . 1 - 7 . 2hx - 8 11 . 0 0 . 022 2 . 0 0 . 46 1310 ° c . × 1 hr 1 . 43 - 1 . 76 179 . 8 - 180 . 4 188 . 4 - 187 . 5 7 . 7 - 8 . 4 9 &# 34 ; &# 34 ; &# 34 ; 0 . 50 1320 ° c . × 1 hr 0 . 81 - 1 . 47 177 . 0 - 177 . 6 182 . 3 - 183 . 3 5 . 8 - 5 . 9 9a 7 . 0 &# 34 ; &# 34 ; 0 . 53 1330 ° c . × 2 hr 1 . 13 - 2 . 02 162 . 0 - 163 . 0 167 . 8 - 168 . 7 5 . 5 - 5 . 9 9b &# 34 ; &# 34 ; &# 34 ; 0 . 56 1330 ° c . × 2 hr 1 . 14 - 1 . 50 159 . 8 - 161 . 8 165 . 6 - 167 . 2 5 . 0 - 6 . 1 9c &# 34 ; &# 34 ; &# 34 ; 0 . 59 &# 34 ; 1 . 52 - 1 . 89 160 . 3 - 162 . 7 165 . 6 - 168 . 0 5 . 2 - 5 . 7 700 - 9d &# 34 ; &# 34 ; &# 34 ; 0 . 62 1330 ° c . × 1 . 5 hr 1 . 64 - 2 . 42 158 . 8 - 160 . 8 163 . 9 - 166 . 0 4 . 6 - 6 . 0 700 - 9e 8 . 5 &# 34 ; &# 34 ; 0 . 62 1320 ° c . × 1 . 5 hr 0 . 79 - 2 . 10 160 . 3 - 164 . 0 169 . 2 - 173 . 3 7 . 1 - 8 . 6 9i 7 . 0 0 . 024 &# 34 ; 0 . 61 1330 ° c . × 2 hr 1 . 24 - 1 . 74 159 . 9 - 161 . 1 165 . 9 - 167 . 2 5 . 9 - 6 . 2 9j &# 34 ; 0 . 026 &# 34 ; 0 . 61 &# 34 ; 2 . 56 - 3 . 03 161 . 0 - 161 . 9 168 . 8 - 167 . 9 5 . 6 - 6 . 0hx - 11a 7 . 0 0 . 024 0 0 . 62 1330 ° c . × 2 hr 0 . 25 - 0 . 31 169 . 5 - 171 . 8 181 . 4 - 184 . 5 11 . 0 - 12 . 7 11b &# 34 ; &# 34 ; &# 34 ; 0 . 64 &# 34 ; 0 . 56 - 0 . 83 163 . 7 - 166 . 0 175 . 1 - 180 . 3 10 . 8 - 14 . 3__________________________________________________________________________ table 4 shows the result of normal temperature - resistance ( kω ), exothermic temperatures (° c .) of applied voltages 220 v and 100 v , dielectricstrength ( v ) and curie point (° c .) measured with respect to positive temperature coefficient thermistors sintered by fixing the additive amount α of sio 2 to α = 0 . 1 % by weight and the additive amount of β of mn to β = 0 . 02 and changing mol % of x , y and z in a ceramic composite of ( ba 1 - x - y - z pb x sr y y z ) ti 1 . 000 o 3 + α wt % sio 2 + β wt % mn . table 4__________________________________________________________________________ii ( ba . sub . 1 - x - y - z pb . sub . x sr . sub . y y . sub . z ) ti . sub . 1 . 000 o . sub . 3 + α wt % sio . sub . 2 + β wt % mnpb sr y normal exotherm temperature di - egree . c . )( mol ( mol ( mol sio . sub . 2 mn temper - difference electric curier %) %) %) ( wt %) ( wt %) sintering ature of strength pointx y z α β pattern resistance 100 v 220 v temperature ( v ) (° c . ) __________________________________________________________________________hx - 2010 . 0 3 . 0 0 . 4 0 . 1 0 . 020 1350 ° c . × 2 hr 1 . 30 - 3 . 14 164 . 4 - 165 . 8 166 . 6 - 169 . 8 2 . 2 - 4 . 3 1000hx - 21a &# 34 ; 4 . 0 &# 34 ; &# 34 ; &# 34 ; &# 34 ; 1 . 71 - 3 . 36 160 . 0 - 162 . 0 162 . 4 - 165 . 6 2 . 3 - 3 . 6 &# 34 ; hx - 21b &# 34 ; &# 34 ; &# 34 ; &# 34 ; &# 34 ; 1340 ° c . × 2 hr 2 . 15 - 4 . 31 159 . 0 - 161 . 4 162 . 2 - 164 . 3 2 . 9 - 3 . 8 1000hx - 22 &# 34 ; 5 . 0 &# 34 ; &# 34 ; &# 34 ; &# 34 ; 1 . 14 - 1 . 80 158 . 7 - 159 . 6 161 . 8 - 163 . 0 3 . 0 - 3 . 7 &# 34 ; hx - 23 &# 34 ; 4 . 0 0 . 43 &# 34 ; &# 34 ; &# 34 ; 0 . 86 - 1 . 20 159 . 4 - 161 . 4 163 . 0 - 164 . 9 2 . 9 - 3 . 9 &# 34 ; hx - 39a9 . 88 &# 34 ; 0 . 40 &# 34 ; &# 34 ; 1340 ° c . × 2 hr 0 . 83 - 1 . 23 159 . 4 - 161 . 4 163 . 0 - 164 . 9 2 . 4 - 3 . 8 1100hx - 39b &# 34 ; &# 34 ; &# 34 ; &# 34 ; &# 34 ; &# 34 ; 1 . 20 - 1 . 94 158 . 3 - 160 . 4 160 . 1 - 163 . 5 2 . 4 - 3 . 8 1200hx - 39c &# 34 ; &# 34 ; &# 34 ; &# 34 ; &# 34 ; &# 34 ; 1 . 31 - 2 . 01 159 . 2 - 161 . 2 161 . 9 - 163 . 7 2 . 4 - 3 . 4 1400 146__________________________________________________________________________ specimens hx21a and hx21b , and specimens hx39a , hx39b and hx39c are experimental data in which normal temperature resistances were differentiated . from the result of table 4 , it is recognized that the temperature difference of the exothermic temperatures of 220 v and 100 v of the applied voltage is relatively stable , though it is inferior in comparison with the example 1 . thus , these compositions can be used in the invention . table 5 is an example in which α and β as well as x , y and z are variously changed . table 5__________________________________________________________________________iv ( ba . sub . 1 - x - y - z pb . sub . x sr . sub . y y . sub . z ) ti . sub . 1 . 002 o . sub . 3 + α wt % sio . sub . 2 + β wt % mnpb sr y normal exotherm temperature di - egree . c . )( mol ( mol ( mol sio . sub . 2 mn temper - difference electric curier %) %) %) ( wt %) ( wt %) sintering ature of strength pointx y z α β pattern resistance 100 v 220 v temperature ( v ) (° c . ) __________________________________________________________________________hx - 279 . 0 3 . 0 0 . 4 0 . 1 0 . 023 1320 ° c . × 1 hr 3 . 99 - 7 . 23 161 . 7 - 162 . 8 170 . 8 - 172 . 4 9 . 1 - 9 . 6hx - 3310 . 0 &# 34 ; &# 34 ; 0 . 1 0 . 021 1350 ° c . × 1 hr 0 . 70 - 1 . 06 161 . 9 - 164 . 2 168 . 1 - 172 . 0 6 . 2 - 7 . 8hx - 34 &# 34 ; &# 34 ; &# 34 ; 0 . 2 &# 34 ; &# 34 ; 0 . 73 - 0 . 97 163 . 0 - 163 . 8 169 . 4 - 170 . 3 6 . 4 - 6 . 5hx - 35 &# 34 ; &# 34 ; 0 . 43 0 . 1 0 . 022 &# 34 ; 0 . 74 - 0 . 98 160 . 9 - 161 . 5 165 . 0 - 166 . 2 4 . 1 - 4 . 7hx - 369 . 5 &# 34 ; 0 . 4 &# 34 ; 0 . 021 &# 34 ; 0 . 71 - 1 . 08 160 . 7 - 161 . 5 165 . 2 - 166 . 9 4 . 5 - 5 . 4hx - 37 &# 34 ; &# 34 ; &# 34 ; 0 . 2 &# 34 ; &# 34 ; 0 . 47 - 0 . 68 162 . 0 - 163 . 0 167 . 4 - 169 . 3 5 . 4 - 6 . 3hx - 38 &# 34 ; &# 34 ; 0 . 43 0 . 1 0 . 022 1350 ° c . × 1 hr 3 . 34 - 5 . 13 156 . 6 - 155 . 1 161 . 4 - 162 . 4 6 . 3 - 6 . 8__________________________________________________________________________ as apparent from the result of table 5 , it is recognized that as the deviation from α = 0 . 1 and β = 0 . 020 increases , the temperature differences of exothermic temperatures of positive temperature coefficient thermistors between 220 v and 100 v of the applied voltage , become great . thus , these compositions can not be used in the invention . in this example , normal temperature - resistance r 25 kω of compositions obtained by variously changing sintering temperatures and exothermic temperatures in which the applied voltages are preset at 100 v and 220 v were measured about ceramic material composite (( bapbsry ) tio 3 + sio 2 ( 0 . 1 % by weight )+ mn ( 0 . 020 % by weight ). the measured results are shown in table 6 . table 6__________________________________________________________________________ normal differencesintering temperature 100 v 220 v oftemperature resistance exotherm exotherm temperature__________________________________________________________________________1320 ° c . × 2 hr 1 . 65 ˜ 1 . 75 159 . 1 ˜ 162 . 9 161 . 5 ˜ 163 . 8 0 . 8 ˜ 3 . 01340 ° c . × 2 hr 0 . 99 ˜ 1 . 30 159 . 0 ˜ 160 . 0 162 . 6 ˜ 163 . 5 2 . 8 ˜ 3 . 61350 ° c . × 2 hr 0 . 96 ˜ 1 . 10 160 . 0 ˜ 160 . 4 163 . 3 ˜ 163 . 8 3 . 3 ˜ 3 . 51360 ° c . × 2 hr 1 . 05 ˜ 1 . 15 159 . 3 ˜ 160 . 1 162 . 7 ˜ 163 . 5 3 . 2 ˜ 3 . 41370 ° c . × 2 hr 1 . 23 ˜ 1 . 39 159 . 5 ˜ 160 . 2 162 . 1 ˜ 163 . 1 2 . 8 ˜ 3 . 11380 ° c . × 2 hr 1 . 62 ˜ 1 . 92 158 . 8 ˜ 159 . 8 161 . 8 ˜ 162 . 6 2 . 7 ˜ 3 . 2__________________________________________________________________________ &# 34 ; 1320 ° c . × 2 hr &# 34 ; element was insufficient sintering and exotherm temperatures change greatly depending on examples . as apparent from the result in table 6 , positive temperature coefficient thermistor elements sintered at 1320 ° c . of the sintering temperature for two hours greatly changed exothermic temperatures depending on the elements due to insufficient sintering , but the width of change or deviation in normal temperature resistance r 25 was smaller than normal width within the range of sintering temperatures of 1340 ° c . to 1380 ° c . it was clarified that the deviation of the temperature differences of the positive exothermic temperatures at the applied voltages of 220 v and 100 v is small and exothermic temperature was almost not affected by the sintering temperature . normally , the positive temperature coefficient thermistors change exothermic temperature in inverse proportion to normal temperature resistance r 25 . the positive temperature coefficient thermistor which uses the abovementioned composition does not substantially change exothermic temperature within the range of the normal temperature resistance r 25 which is normally used . therefore , there is no great variation for the exothermic temperature characteristic of the element even though the sintering temperature becomes slightly up and down and the normal temperature resistance r 25 is varied , at the mass production . the exothermic devices used in table 6 are included in the present invention . specimen hx - 18a which is shown in table 2 of the example 1 was formed in an arc - shaped segment of 1 . 32 cm in outer diameter , 0 . 78 cm in inner diameter , 0 . 35 cm in thickness and 100 ° at a central angle . the specimen was sintered at 1330 ° c . for two hours , as shown in fig4 both sides of the obtained elements 5 &# 39 ; were applied with electrodes 6 &# 39 ;, and the elements were fixed between a pair of terminal plates 7 &# 39 ; under pressure to prepare an exothermic device 4 &# 39 ;. as in the embodiment as shown in fig5 the exothermic device 4 &# 39 ; was set around a core 3 in the tank 2 ( fig5 ). insecticidal liquid ( 45 ml in every cases ) was filled in the tank and consuming time of the total amount of the insecticidal liquid was measured when the exothermic device 4 &# 39 ; was heated at 100 v and 220 v . the result is shown in table 7 . table 7______________________________________ evaporating and diffusing time of insecticidal liquid ( hr .) applied applied voltage of voltage ofr . sub . 25 l ( kω ) 100 v 220 v difference______________________________________1 0 . 45 310 283 272 0 . 47 307 282 253 0 . 52 311 285 264 0 . 59 318 289 295 0 . 69 311 281 306 0 . 71 320 288 327 0 . 82 345 311 348 1 . 00 360 325 359 1 . 25 362 328 3410 1 . 32 378 341 37avarage -- 332 301 31______________________________________ as apparent from the result of table 7 , the time for consuming the total amount of the insecticidal liquid in every specimens is short in the case of the applied voltage of 220 v in comparison with the case of the applied voltage of 100 v . however , the difference of time is only thirty one hours at the longest . according to the tests , it was recognized that there caused the difference of twelve hours for the consuming time of the total insecticidal liquid of 45 ml if there is a difference of 1 ° c . at the exothermic temperatures of the applied voltages 220 v and 100 v . therefore , if the temperature difference is 7 ° c ., the difference of the consuming time is eighty four hours . the exothermic devices used in table 7 are included in the present invention . as described above , according to the present invention , there is almost no difference at the exothermic temperature of the exothermic device , and stable characteristic can be obtained according to the difference of the applied voltages . in case more than two positive temperature coefficient thermistor elements are incorporated in the exothermic device , it is not necessary to arrange the normal temperature resistance in the respective elements . thus , it can assemble the exothermic device by arbitrarily selecting elements . in the above - mentioned examples , the exothermic device of a liquid - type electric mosquito - fuge apparatus is described , but the present invention is not limited thereto . the present invention can be widely utilized to a heater for preventing freezing and other heating sources .