US3779948A - Vitreous compounds with bistable electrical characteristics - Google Patents

Abstract

A new class of vitreous compounds having bistable electrical characteristics, that is to say, two different states of electric resistance is described. The new class of vitreous compounds can be represented by the general formula (1):

Description

United States Patent [1 1 Loriers et al.

[451 Dec. 18, 1973 VITREOUS COMPOUNDS WITH BISTABLE ELECTRICAL CHARACTERISTICS [75] Inventors: Jean Loriers, Meudon; Rudolf Heindl, Fontenay Aux Roses, both of France [22] Filed: July 28, 1971 [21] Appl. No.: 166,777

[30] Foreign Application Priority Data July 31, 1970 France 70.28387 [56] References Cited UNlTED STATES PATENTS 3,598,762 8/1971 Futaki et al 252/518 2,862,891 12/1958 .lonker et al. 252/518 X 3,258,434 6/1966 Mackenzie et al 252/519 3,469,729 9/1969 Grekila ct al. 106/47 R 3,503,902 3/1970 Shimoda 252/518 X Primary ExaminerCharles E. Van Horn Aztorney.1ames and Franklin [57] ABSTRACT A new class of vitreous compounds having bistable electricalcharacteristics, that is to say, two different states of electric resistance is described.

The new class of vitreous compounds can be represented by the general formula (1):

2-.r-2z z 2+r+z i-u n 3 12-: 1

1) wherein the letters have the usual meaning of the elements in the Periodic Table with the exception of Ln which designates as a whole a rare earth belonging to the group of lanthanides, such as lanthanum La, or yttrium Y, whereas x, y and 1 each represent numbers between 0 and l, which can separately and simultaneously be zero, which are connected by relations of ionic equilibrium, and preferablyrespond to the inequalities y 0.5 and z 0.3 An example of compound having the formula (1) is Ca Na Al V 0 (ll) 10 Claims, 3 Drawing Figures VITR-EOUS COMPOUNDS WITH BISTABLE ELECTRICAL CHARACTERISTICS The object of the invention is a new class of vitreous compounds having bistable electrical characteristics, that is to say, two different states of electric resistance. It also relates to a process for obtaining same and applications thereof. 4

Vitreous compounds having such characteristics are already known. It is possible, for instance, to mention French patents, 1,445,528 and 1,351,433 as documents illustrating the prior art in this field. Patent 1,445,528 describes binary vitreous compounds. Patent 1,351,433 which is used more particularly as a bibliographical reference in the present description, describes ternary or quaternary vitreous compounds of the type AsTel, AsTeSe, AsTiSe, VOP, VOPBa, VOPPb or AsBTiO. Such semi-conductive compounds are used in electrical elements where they are combined with an electrical signal source to take advantage of their two states of resistance at least. Said electric elements are used in the technique of switching, in solid state electronic amplifiers and oscillators as well as storage elements, among other things, as the aforesaid French patent explains in detail.

The state of the art with respect to this question can be further illustrated by the following documents R. and O. l-lOLZlNGERs article headed Feldabhangige Widerstandsanderung in Glasern" in the German publication Zeitschrift fur angewandte Physik, vol. 28, No. 4, 1969, pages 196-201, relating to a vitreous compound for electric devices in a conductive and resistant state, which can comprise and adequate mixture of B CaO and V 0 oxides.

Swiss patent No. 490,728 (SIEMENS A.G.) relates to a semi-conductive switching device without a junction. A vitreous compound is formed from a mixture of V 0 and SrCO United Kingdom Pat. No. 1,168,107 (HITACHI Ltd.) can also be mentioned it relates to a process for manufacturing a thermistor consisting of a sintered mixture of V 0 and a combination of various oxides such as Na, Ca, Al (page 4, example 4), and United States Pat. No. 3,258,434 assigned to (GENERAL ELECTRIC Co) relating to a semi-conductive glass containing CaO'2B O V O Fe o -Al- O (column 6, example X) as a constituant.

However, the prior art compounds are not satisfactory in all fields of application, and technicians think it desirable to develop vitreous compounds with, notably, improved mechanical and electrical properties. The object of the present invention is, therefore, vitreous compounds having electrical and mechanical properties very superior to those of similar, known compounds.

The new class of vitreous compounds can be represented by the general formula (1) 2-z-2: 2+1+z t-u ll II IZ-ar -T y O.5 and The chemical composition of the new vitreous compounds appears, at first glance, to be rather complicated. They all, however, have a common basic matrix of formula (11) Ca Na Al V 0 This particular compound corresponding to the formula (I) wherein x=y=z=0.

The compound of formula (II) has bistable electrical characteristics suited to the requirements of the invention. Its mechanical and electrical properties are superior to those of the known compounds. For example, the difference in resistivities between the conductive and resistant states is at least 10 times as great as that corresponding to the prior compounds.

The other compounds of the invention can be obtained from the basic matrix of formula (ll) by the introduction of the rare earth Ln and/or iron Fe or fluorine F.

In certain cases, bistable glasses can also be obtained by combining several compounds corresponding to formula (I), one of which is, for instance, the basic compound of formula (ll). The products obtained no longer correspond to formula (I) but they retain bistable electrical characteristics.

A series of examples illustrating said new class of vitreous compounds will be given hereinafter. The common characteristic of these substances is that they have bistable electrical characteristics and that they are vitreous, that is to say, they do not show definite lines in X-ray diagrams (Debye-Scherer diagrams). Said new vitreous compounds are mechanically and chemically very stable, contrary to most of the known compounds which are very friable and very oxidable glasses containing As, Te, l or the like.

The new vitreous compounds are prepared under critical conditions for precursor products of the chemical elements of formula (l), notably oxides and salts such as carbonates. The mixture of said precursor products in substantially stoichiometric proportions corresponding to formula (I) should be heated at high temperature for along period of time to obtain vitreous compounds.

The invention therefore also relates to a process for obtaining vitreous compounds corresponding to the aforesaid formula (I) by the intimate contacting of precursor products with the formation of a mixture providing the elements of said compounds in substantially stoichiometric proportions and a thermal treatment, wherein the said mixture is heated for at least 5 hours at a temperature higher than 1,300C.

Generally speaking, periods of heating from 6 to 12 hours are suitable, at temperatures of 1,300 to 'l,400C, at 1,350C for example. Melting at insuffciently high temperatures, or for too short periods of time, does not enable vitreous products to be obtained. lf the conditions provided for in the invention are not respected, products which crystallize on cooling are finally obtained.

The invention will now be illustrated, while in no way being limited by the following examples EXAMPLE I Preparation of the compound ca wa m V 0.

(molecular weight 588.95) There is prepared an intimate mixture comprising A1 0.5 mole or 50.97 g

CaCO 2 moles or 200.18 g

Na CO 1 mole or 106.00 g

V 0 1.5 mole or 363.8 g

The total weight of the mixture is therefore 720.95 g. The mixture is then heated open to the air in a platinum crucible at 650C for 2 hours, at 750C for 2 hours and then at 1,350C for 6 hours.

Chemical analyses effected during heating show that the sodium content does not vary.

The product obtained is a vitreous body corresponding to the aforesaid formula (II) and having two different states of electric resistance Electric measurements were carried out to determine the properties of the new product. FIGS. 1 to 3 show the assembly conditions and results obtained.

FIG. 1 is a general diagram of the electric circuit permitting voltage-current characteristics to be obtained.

FIG. 2 is a detailed view showing the assembly of the sample containing product (II).

FIG. 3 is the voltage-current curve obtained.

FIG. 1 shows, diagramatically, the assembly used. A continuous 300 volts power supply 1 is connected to a throw-over switch 2 by a potentiometer 3. The throwover switch 2 is connected, on the one hand, to earth through a resistor 4 or read resistor (100.) and a voltmeter 5, as well as to the input of a voltage-current curve tracer 6 and, on the other hand, to sample 7 to be tested through a resistor 8 (501(0). The other terminal of sample 7 is connected to earth by a resistor 9 and a conductor 10 connects the other input of tracer 6 to one of the terminals of resistor 8.

FIG. 2 shows a detail of the assembly or sample 7.

Two cylindrical graphite pellets, numbered 11 and 12, and between which is disposed a pellet 13 of the sample of the product to be tested, are inserted between the conductors adapted to connect sample 7 to resistors 8 and 9 respectively (FIG. 1). Pellet 13 is maintained between the graphite cylinders by a conductive coating such as a silver paint put on the market by the German firm DEGUSSA. Pellet 13 is about 0.1 mm in thickness.

FIG. 3 is the voltage-current curve recorded with the device for sample 13 containing compound Ca Na- Al V (II). The voltages are shown in abscissa (volts) and the current in ordinateslmillian aeres) The graph shows that compound (11) has two states: 1. a resistive state corresponding to values V= 140 V, I=0.l2 m A or R 117 X 10 .0

2. a conductive state corresponding to the values I=4 m A or R 137 X10 0.

On the curve, portion (A) corresponds to the resistive state and portion (B) to the reducer state.

EXAMPLE 2 which sodium fluoride is incorporated in the amounts 6 given, are subjected to the same thermal treatment as described in example 1.

1.86 mole Ca CO, {86167 g 1.0 mole wa co, 1 106.00 g 0.5 mole A1 0, 50.97 g 1.5 mole V 0 363.80 g 0,14 mole NaF 5.88 g Total weight 712.817 g A glass having a molecular weight of 586.977 g is obtained.

Formation of glass will not occur with fluoride ion contents higher than 0.14.

EXAMPLE 3 To obtain the product Ca Na- Fe V 0 (formula m x 0 y 1 z 0) as well as the product Ca Na A1 Fe V 0 This latter product, which does not correspond to the stoichiometric composition given in formula (I) can be obtained from the basic compound Ca Na A1 V 0 (11) and from the compound Ca Na Fe V3012. I I

3a. The mixture corresponds to the compound Ca Na Fe V3012 0.5 mole Fe; 0 79.85 g

and comprises 2.0 moles CaCO 2()() g 1.61m. Na, CO 106.00 g

0.5 mole V 0 272.00 g

Total 657.85 g

W This mixture is heated in a platinum crucible open to the air at 650C for 2 hours then at 800C for 2 hours. A reaction product is obtained which is ground fine.

3b. The product (3a) is mixed with 20 moles of product (II) also finely ground. The entire mixture is heated at 1,350C for 6 hours in a covered platinum crucible. The glass forms on cooling.

EXAMPLE 4 EiiAMbLES To Obtain the product Ca Y Na V 0, This example illustrates a variant of the vitreous comp iti n which can be Ob ed by m x ng a mpou containing yttrium and the basic produce of example 1.

The following mixture is first prepared 0.5 mole Y,O,-, 112.92 g 2.0 moles CaCO, 200.00 g 1.0 mole N2i,CO 106.00 g 1.5 moles V,O, 272.00 g

This mixture is heated at 650C for 2 hours and at 800C for 2 hours.

The resulting product is ground. An amount of 0.2

mole (138.18 g) of this finely ground compound is umns of the table the values of indices x, y and 2, corresponding to formula (1) are given. The glass formula is given in the fourth column and the amounts in moles and grams of the precursor products used are procedure described in example 1. In the first three 001- 5 given in the last column, with their designation.

. 553 5-- Precursor compounds (amounts in moles and in g) EXAMPLE 6 to 24 The following table gives details of a series of glass compositions which can be obtained according to the Ex y z Formula Y o 11.29 g. 6 1. 111.30 g.

. no... 11.29 g. CO3N212, 111.30 g. 1 11091120. 337.62 g.

La OK. 16.29 g.

La.0 16.29 g.

ZOQ, 11.29 g.

05. 00 N11 111.30 g. 00, 211010.) 911.0, 375.14 g.

0 0.10 0.10 ca.,.Ln.,.Na...A1o.,,.1=e..,,v.0,................................. s. 00.01.180.16 1;.

05. La Q-pu v.0.

711090 1.. 911.0. 337.62 g. Fe O 7.97 g.

0.12 0.10 0.10 Ca,,mqLn Na, A|1,, Feo, V O F co' ca, 16s.

La o ou Y O O 0.10 Ca sLno oNag.16Al11 sFe1 V O,

La o ou Y O 0.12 0.20 0.10 011mm...1-1a .1., .1=1=.,,.v 0,.1 ....2 CO Ca, 168.15 g.

3 L e a z a 0.20 0.20 Ca1.1Lno oNa Al6 Fe V Ol2............................... CO Ca, 140.12 g.

La O ou Y O lLa O;,, 16.29 g. 11.0., 11.29 g. CO Na 116.6 g. 111010 1., 91-1 0, 300.11 g. v.0..2721s5 Ca gLno uNagiggAlu gFengv o 135F042 CO Ca, Y O ou La O 10, CO Na 116.6 g.

A1(N0.)., 911.0, 300.11 g.

3 g g g 2 g 0 u m u e W. e ..m...

0% .2 2 M m w o MCY .1 e e. 2 91 H a g H g H. & 1 0.z&1.. 2 88%H9 99 g 92 92 g .93.HH .O

a 1 7 1 v) \U 3 3) 2 v v 2 pq lvw a aMQM SM MNaMQJ Sa 1w a aflaw .1. 0 NO N0 N0 0 3N0 a 0 a N2 (z (z O N wm m n mwmm m mn wmm mmmnm m v .moA ,v ...v .00 -v .v .Av .5. bw wem .wfimmmgwmfiimmmwfiem .11110 11 01111 11 1 1111 01. 10011110 u U m m o. m n n F n F H J m m m m m. m nm N m 1 n O1 r 0. u 01 H 3 1 n W v 0 v. w 0. n. o. .6 v 1 v N M w m m V W o M M m n I F 1 1 I .0 0 m M w 1 n 0 L 1| 2 a l a A a 0 m A n a a 1. .N m a a 2 a m 6w aw m C C C C C C C 0 0 0 0 0 O 0 0 0 0 1.. l 0O 0 O O O 0 3 0 0 M 0 n 0 2 0 4 0 0 0 O 6 7 8 9 W H U TABLE- Continued Ex x y 2 Formula 19 0 02 1' Ca,,5 Ln},2;NaQMLVQOJ 1.40, CO Ca, 140.12 g.

Precursor compounds (amounts in moles and in g) co caff 2T13'" 0.1.0., 16.29 g. Y.o,, 11.29 g. 1.12. (30.1%,, 118.72 g. I. AI(N0..),,. 911.0. 375.14 g. 1 v,o,. 272.85 g.

l 52, 0.12, Y o ou L0 0 1.52, CO -,Ca. 152.13 g.

l a z g 1.1120,, 16.29 g.

5, mo... 7.97 g.

22 Cal,4(lLn0 24Na2 3fiAlojFe0,|VHOH QBFQJZ 1 0, CO Ca, g.

23 0 0.20 0.24 Ca..5.1.11....1 1a A1., ..1=e.,,.v,0,

0.12, La o ou Y O La O 16.29 g.

Y O 11.29 g.

1.12, coma, 118.72 g.

0.9, Al(NO 91-1 0, 337.62 g.

0.05, Fe O 7.97 g.

0.12, FNa, 5.036 g.

.................... 1.52, CO Ca, 152.13 g.

1.12. 00,103,, 1 0.8, A1 No, 911,0, 30011 g. 0.1. n.0,. 15.95 g. 1.5, v,o,, 181.90 g. 0.12, FNa, 5.036 g.

- wherein the letters have the usual meaning of the elements in the Periodic Table, with the exception of Ln which designates an element which is a part of the group of rare earths belonging to the class of lanthanides and yttrium, whereas x, y and z each represent numbers in the range of 0 to l, which are bound to-' gether by ionic equilibrium relationships.

2. The compound of claim 1 wherein x is zero.

3. The compound of claim 1 wherein y is zero.

4. The compound of claim 1 wherein z is zero.

5. The compound of claim 1 wherein x, y and z are simultaneously zero, the said compound corresponding to the formula Ca Na Al V 2 6. The compound of claim 1, wherein the element Ln is lanthanum and z is greater than 0.

7. The compound of claim 1 wherein x, y and z comply with the inequalities wherein the letters have the usual meanings of the ele- 1 ,300 and 1 ,400C. 65

40 8. A process for the production of a compound of formula (I):

2.r-2z z 2+z+z l-u n V3 u -1 ments in the Periodic Table with the exception of Ln which designates an element which is a part of the group of rare earths belonging to the class of lanthanides and yttrium, whereas x, y and z each represent numbers in the range of O to l, which are bound together by ionic equilibrium relationships, said process comprising the steps, (a) preparation of an intimate mixture of precursor products containing the elements of said compound in substantially stoichiometric proportions, (b) heating said mixture at a temperature higher than about 1,300 C for at least 5 hours and, (c) cooling of said heated mixture to normal temperature, the desired vitreous compound forming during said cooling.

9. The process of claim 8, wherein the heating (b) is carried out for about 6 to 12 hours.

10. The process of claim 8, wherein during the heating (b) the temperature is maintained between about

Claims (9)

1. 2. The compound of claim 1 wherein x is zero.
2. 3. The compound of claim 1 wherein y is zero.
3. 4. The compound of claim 1 wherein z is zero.
4. 5. The compound of claim 1 wherein x, y and z are simultaneously zero, the said compound corresponding to the formula : Ca2Na2Al V3O12
5. 6. The compound of claim 1, wherein the element Ln is lanthanum and z is greater than 0.
6. 7. The compound of claim 1 wherein x, y and z comply with the inequalities x<0.15 y<0.5 and z<0.3
7. 8. A process for the production of a compound of formula (I): Ca2 x 2zLnz Na2 x z Al1 y Fey V3 O12 xFx (I) wherein the letters have the usual meanings of the elements in the Periodic Table with the exception of Ln which designates an element which is a part of the group of rare earths belonging to the class of lanthanides and yttrium, whereas x, y and z each represent numbers in the range of 0 to 1, which are bound together by ionic equilibrium relationships, said process comprising the steps, (a) preparation of an intimate mixture of precursor products containing the elements of said compound in substantially stoichiometric proportions, (b) heating said mixture at a temperature higher than about 1,300* C for at least 5 hours and, (c) cooling of said heated mixture to normal temperature, the desired vitreous compound forming during said cooling.
8. 9. The process of claim 8, wherein the heating (b) is carried out for about 6 to 12 hours.
9. 10. The process of claim 8, wherein during the heating (b) the temperature is maintained between about 1,300* and 1,400*C.

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