DE1758044C3 - Use of transition metal silicon alloys as contact pieces for thermoelectric arrangements and processes for the production of blanks for such contact pieces - Google Patents

Description

The main patent 1 558 644 relates to the use of an alloy of the general additions Me ¹ and Me "one of the metals of groups IVa, Va, Via, Vila and VIII of the periodic table, with the exception of the tccdium, y - ■ 0, 5 to 0.9 and .v is 0.05 to 0.35, as electrically neutral contact pieces for thermoelectric arrangements made of semiconductor alloys between manganese and silicon,

ίο iron and silicon or germanium and silicon. Contact pieces that are used in the construction of thermo-ciektrischen Arrangements must serve as part of a contact bridge for the thermocouple legs if possible the same expansion coefficient as have the semiconductor material, so with a temperature change the contact does not cause excessive mechanical stresses. The Konlaktstück must have a high level of non-resistance and a high Have temperature and temperature change resistance. Must be in an aggressive atmosphere the contact piece must be corrosion-resistant. Furthermore, by contacting the semiconductor body with the contact piece no umdotienine or even the formation of a p-n barrier layer take place. Should the contact piece as a contact bridge in one Thermogencrator are used, it must have a high electrical and thermal conductivity, because the efficiency of a thermogenerator depends, among other things, on these parameters.

Fulfill contact pieces made of an alloy with the general composition mentioned -ille mentioned Calls. In particular, because of their metallic component, they have great hardness and Breaking strength. The contact pieces are geeir.net in a special way for thermal generators. Have attempts show that thermocouple legs that are contacted with said contact piece without further can be operated up to over 1000 C. Because the efficiency of a thermogenerator too depends on the temperature of the heat source, a high degree of efficiency can be achieved with the contact piece. The invention is based on the object of specifying mixing ratios for the contact pieces, which have a higher electrical conductivity while maintaining the advantages described, whereby the efficiency of a thermal generator is optimized.

According to the invention, this object is achieved in that for a Gcrmanium-silicon semiconductor body the metal Me ^{1 is} one of the metals tungsten or molybdenum and y is 0.65 to 0.75.

When producing the blanks of these contact pieces, a binary alloy is preferably first made melted the two metals in the appropriate mixing ratio, and then this is Alloy with silicon melted together in the desired mixing ratio. The advantage lies in the separate, preceding melting of the binary alloy. At least towards the Alloy component with the highest melting point is the melting point of the binary alloy lowered itself and approached the melting point of silicon. This is when melting together The tertiary alloy largely prevents evaporation of the silicon, and it can be ternary Gain alloys with a defined composition, which are based on the thermal expansion coefficient of the Semiconductor body, which for example consists of a GeSi-

Alloy exists, precisely matched
Procedures can largely ho

g are fitted. With this

largely homogeneous, tension-free grooves and crack-free blanks are produced.

In Table 1, under (1) his (U) are compositions listed for contact pieces that correspond to the specified Area correspond.

table

Schmcl / -
punk'
C. Linear
Out
elongation
coefficient \
[10 "" C '] Thermal conductivity
ability s-
[caf- 5 '
cm " ¹ C '] [/ leklrische
conductivity
bc / oücn on
GtV ₁ Sl ..: OxAiialion · .-
is called HMHI Γ _Gc , _: , s ,, ₇ - 1330 0.51 0.01 - lO (M) Well [12- cm '] WHERE" " Π <Mo _11-7 Ke ₀₁ A ^ Si ₁ , " 1640 0.52 0.22 250 medium 2t (Mo ₁₁ , ^, Co ₁₁ ,,,) ,,, _ls Si _n , _v , 1,620 0.52 0.22 500 Well ¹ (Mo _0- , _i7 Co _0i ,.,) _0il2 Si _0i,. 1500 0.51 0.21 350 very good ^α ) (Mo _{1) i7:>} Ni _n- ., ₅ ) _{l) i2} Si _0- , 1610 0.52 0.22 450 Well 51 (Mo ₀₇ Ni ₀₃ I _0-17 Si _{0 M} 1 6 (K) 0.52 0.21 350 Well ή) (Mo _0-75 Pd _0-2 A _- ^ Si ₀ ' ₇ . 1 660 0.52 0.22 W) Well 7) (Mo _0-117 Pd ₀ ^ V ₁ KSi _n ,,, i 550 0.51 0.21 250 very good *> (W _o ., _I; Fe ₀ ,, A., Si _o . _K 1680 0.51 O, -23 2 ^;; ) medium '' I (W _0-7 ., Co ₀ , ₂ ;,) _0- ., Si _{0 ,,} 1770 0.51 0.23 600 medium 10) (W _{0 67} Co ₀ .,.,) ",, Si ,,, _B 1620 0.51 0.22 350 Well 'in (w _o ; ₇₅ Ni _o ; ₂ A _i ;, si _o ; ₇₇ 1750 0.51 0.24 550 medium '1 2) (W _{0 fi7} Ni _{0 T} ,) _{o li;} Si _n ,, 1 675 0.51 0.22 400 Well i3) (w _{o ;, 5} Pd; _-25 ) _o ; ₂₅ si _o ; ₇₅ 1700 0.51 0.24 4 (X) Well M) <W _0-B7 Pd _0i:, A _i2 Si _0-s 1,700 0.51 0.23 300 Well

To demonstrate the advantages of the contact piece painting according to the invention, Table 1 contains the melting point, the coefficient of linear expansion, the thermal conductivity κ and a statement about electrical conductivity and resistance to oxidation. For comparison, the same values are given in the first column of the table for a GeSi alloy. The stated values can fluctuate by approximately 5%. In the case of the coefficient of expansion, however, the fluctuations are below 1 "/". For the alloy Cie _{0-: t} Si _{n 7} , an average value was given as the electrical conductivity, which depends on the doping. The electrical conductivities given for the contact gap materials are based on the conductivity of the Cic _0, Si based _{0 7} alloy. Ls ^ t of the table can be seen that the electrical conductivities, for example, the materials (2), (4), (9) and (II) the durchschnittlicheil conductivity value of said in the parent application mixture ratios for Kontaktstückmatcrialien The increase in electrical conductivity was achieved by increasing the proportion of heavy metals (Mo and W.) The table also shows that this increase in electrical conductivity did not impair the other values. The oxidation resistance is in some cases considerably improved .

It is advantageous for the production of an according to the invention Contact piece the binary alloy and the silicon in a vertically placed, closed at the bottom Bringing in the melting tube and inductively melting it by means of an H F field, the melting tube at least when the melt solidifies in rotation to set the tube ratio and a speed should be chosen, in which a depression in the surface of the melt is created, the depth of which is at most approximated the radius of the melting tube cntsorig. When the melt solidifies, the melting tube can move into Direction of the pipe axis lowered from the HK-FcId will.

The advantage of this method is on the one hand in one good homogenization of the tertiary alloy. But above all it is due to the rotation under the specified Conditions prevents cracking in the solidified melt, which normally occurs because the coefficient of expansion of the contact piece materials according to the invention is negative and the materials therefore expand as they solidify. By rotating at the specified speed, at which one A depression in the surface of the melt becomes a zone of reduced density along the pipe axis formed of the melting tube. A zone of increased density lies in the area of the melting tube wall. In that zone of reduced density came in. the molten alloy expand as it solidifies and states of stress during solidification expand, and states of stress during solidification are reduced, which are triggered by pressure on the side wall of the melting tube and which cause cracks to form η .ch pull yourself.

It should also be emphasized that the advantage already described in this production process as well the binary alloy that was melted first is retained. Table 2 shows the Melting point of the binary alloy and its alloying components are given. The numbers of the examples correspond to the numbers in Table I. The melting point of the silicon is given as a comparison. It can be seen that the melting point of the binary alloy is the melting point of silicon partly very strong compared to the respective alloy component with the highest melting point is approximated.

5
Table 2

10

Si 1415 Melting point Men M (I ₁₁ 7 IC ,,;, 22M) Mei Mo _0i 7-, Co _n2r , 2150 15.V) (I-C) (I) Ml) ,, _ili7 C () _Oi ;, _: , 2030 HiIO (Mon) 1495 (Co) (2) MiO.7sNin.25 1830 2610 1495 (3) Wed> ,,,, Ni _o , ₃ 1800 2610 1452 (Ni) (4) Mon ₀₁₇₅ Pd ₀₁₂₅ 2240 2610 1452 (5) M ¹¹ O ₁ U ₇ Pt ¹ O. :) :! 2100 2610 1550 (Pd) ((O W _{n> 117} Fc _Oi : _M 2300 2610 1550 (7) W _n . 7, Co ₀ ,,, 3000 2610 1539 (Fe) (8th) W _{0l (1T} Co _{0. M} 2800 3380 (W) 1495 (Co) ( ^l >) W ,,, 7, Ni _0. , .-, 2000 3380 1495 (10) W _n , ";Ni". _M. ■ t920 3380 1452 (Ni) (Π) W ", 7, Pd _o , ₂ , 3180 3380 1452 (12) W ₀ . _nJ Pd ",, _a 3100 3380 1550 (Pd) (13) 3380 1550 (14) 3380

In the following the invention is based on the FIGS. I and 2 explained in more detail by way of example, the Fig. 2 shows the embodiment of a device shows, with which the manufacturing process according to the invention can be carried out advantageously.

Fig. 1 shows a thermogenerator. in the p- and n-conductive thermocouple legs 1 are electrically connected at their cold and warm soldering point by means of contact bridges 3 so that they are electrically in series and thermally parallel and each of their cold and warm soldering points in one plane, namely the cold or warm side of the thermogenerator. On the contact bridges of the cold and warm scite of the Thermogcncrators a thermally conductive and electrically insulating Matcrialschicht 5 is applied, the z. B. can be made of aluminum oxide or Berylliumo.xyd. On the warm side of the thermal generator, a heat exchanger 7 is placed, which is provided with a passage 8 for a hot liquid heat exchange medium. The temperature of this heat exchange medium is over 1000 ⁰ C. On the cold side of the thermal generator is a heat exchanger 6 is placed for a gaseous heat exchange medium.

The thermocouple legs 1 consist of a germanium-silicon alloy. The p-type thermocouple leg is for example by doping with boron, gallium or indium and the 5c η-conducting thermocouple legs produced by doping with phosphorus, arsenic or antimony. The thermocouple legs 1 are contacted with contact pieces 2 and 3 according to the invention, their Mixing ratio is adapted to the expansion coefficient of the semiconductor in question and with respect to the electrical conductivity is optimized. The contact piece 3 is used as a contact bridge for electrical Connection of two thermocouple legs 1 is formed. Via the contact pieces 2, the thermal generator the electrical energy is taken.

The thermocouple legs 1 can be fused onto the contact pieces 2 or 3. However, it is advantageous to use a solder layer 4 for connecting a thermocouple leg to the contact pieces 2 b / w. 3 to be provided. It is particularly advantageous in this case, contains a solder to be used are in the palladium and silicon Legicrungskomponcnten and a drille Lcgicrimgskomponcnte contained as metal micro ¹ or Mc "in the alloy of the Kontaktbrückcnmatcrials. This solder layer to obtain a Kontaklzonc, in which the contact bridge material is continuously converted into the semiconductor material of the thermocouple legs.

In Fig. 2 shows a device for carrying out the manufacturing process. it consists of two parts, one of which is used for the rotation process and the other for heating the batch. The rotating device contains a rotating clamping tube 9 with a clamping part 10 into which the Melting tube 11, which can be made of quartz, for example, can be inserted and clamped centrally. Additional cooling, for example with an air stream, can be provided for the melting tube 11 being. The clamping tube 9 is guided by ball bearings 12 which are held in a metal sleeve and can be driven by means of a motor 13 with adjustable speed. To control the speed of the Melting tube 11, a tachometer 14 is provided. Another is located in the clamping tube 9 Pipe 15 through which z. B. Argon is introduced to create an inert atmosphere. The heating part consists of a high-frequency induction coil 16, which is fed by a high-frequency generator. The induction coil is arranged so that it completely encloses the melt charge 17. Every single one Casting is prepared by weighing in the appropriate amounts of the solution components. The already well mixed starting material! is introduced into the melting tube 11 and by means of the high-frequency field melted. It is favorable to have the melting tube 11 already during melting to rotate, so that a good mixing of the alloy is guaranteed. After melting the rotation is continued during solidification and the melting tube 11 in the direction of its tube axis lowered from the induction coil 16.

It is in the fig. 2 the depression 18 in the surface of the melt charge 17 can be seen, which indicates that the speed has been selected correctly and that a zone of reduced density has formed along the pipe axis. The speed depends on the inside diameter of the melting tube 11 and, because of the viscosity and the temperature of the melt, on the material composition of the charge. For example, can be an alloy of the composition (Mo _{0 75} Co _{0f "ä) 0ils} Si _0iS 2 in a melting tube 11 mils an inner diameter of 12 to 13 mm at speeds of 700 to 800 revolutions / min, rißfre melting.

After solidification, the melted piece is removed from the melting tube. The manufactured « homogeneous and crack-free alloy is obtained in the form of cylindrical bodies. The contact pieces will be cut off from this cylindrical body as disks. Is a special form of the contact piece required, a corresponding reworking can be carried out.

1 sheet of drawings

Claims (4)

Patent claims: 1. Use of an alloy of the general composition composition (MeUIe ",") _r Si, where Me ¹ and Me "are one of the metals of group IVa, Va. Via. Vila and VIII of the periodic table, with the exception of teclinetium, ν 0.5 to O ₁ ¹ ) and ν 0.05 to 0.35. being electrically neutral Contact pieces for thermoelectric arrangements made of semiconductor elements between manganese and silicon, iron and silicon or germanium and silicon, according to patent 1 558 644 with the proviso that for a germanium-silicon foil body the metal Me ^{1 is} one of the metals tungsten or molybdenum and y = 0.65 to 0.75. 2. Use of an alloy of the composition mentioned in claim 1 with one of the the following financial compositions (M e) ",,. Si _0- , (Mo _11n Co ,, ..;,) ,,., ^ Si ₁₁ -,., (Mo ,,,, (tCiy.,.,) ,,,,. ^ ,,,,, (Mo. 7 .-, Ni _0- O .-,) ,, ..., Si ₁ , _ "(Mo _0-7 Ni _11-3 X _1-17 Si ₁₁ ,.,:, (Mo _f . _-7 , Pd _{n- ;;} , I _11-22 Si _0-7 . (Mo _0-117 Pd ₁ ,., I _0-111 Si,., .., 2.1 2.3 2.4 1 s 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 for the purpose mentioned in claim 1. 3. Process for the production of blanks for contact pieces from alloys of the compositions mentioned in claims 1 and 2, in which the metals Me ¹ and Me "are melted together in the appropriate mixing ratio and then this binary alloy and the silicon are melted at least once in the corresponding mixing ratio , characterized in that the binary alloy and the silicon are introduced into a vertical melting tube (11) closed at the bottom and inductively melted by means of an HF field, that the melting tube is set in rotation around the tube axis at least when the melt solidifies and that a speed is selected at which a depression (18) is created in the surface of the melt, the depth of which corresponds at most approximately to the radius of the melt tube. 4. The method according to claim 3, characterized in that that the melting tube (11) when the melt solidifies in the direction of the tube axis from the hiF field is lowered.