Dipping process for the production of transparent, electrically conductive, augmented indium oxide layers

In a process for producing transparent, electrically conductive, augmented layers of indium oxide by means of a dipping process, during which the substrate to be coated is dipped into a solution containing hydrolyzable compounds of indium, whereupon the substrate is withdrawn from the solution, is dried, and tempered at temperatures of up to 500.degree. C., a dipping solution is used which, in addition to the indium compound, contains at least one additional hydrolyzable compound of an element in the 2nd, 4th or 5th main groups, in the 1st, 2nd, 4th, 5th or 8th subgroup of the periodic system of elements, or of the rare earths.

DESCRIPTION OF THE INVENTION 
1. Technical Field of the Invention 
This invention relates to a dipping process for the production of 
transparent, electrically conductive, augmented indium oxide coatings. 
2. Background Art 
There is great interest in transparent, conductive oxide coatings for the 
purposes of heat reflection, for displays, heating (e.g., defogging), and 
much more. As compared to metallic layers, oxide layers are characterized 
by considerably greater chemical and mechanical stability and, therefore, 
their suitability for being employed on the exterior. Augmented indium 
oxide differs from the familiar oxide layers, such as fluoro-augmented tin 
oxide, antimony augmented tin oxide, and cadmium stannate, by very high 
conductivity at high transmission values. According to the current 
state-of-the-art, indium oxide is augmented with tin oxide. Other 
augmenting agents have also become known for In.sub.2 O.sub.3 -layers 
manufactured in a vacuum and spray process, such as In.sub.2 O.sub.3 
charged with Cd, Sb, Ti, Zr, and fluoride; see R. Groth, Phys. Stat. Sol 
14: 69 (1966), but they have not found any practical application. 
Quality and economic feasibility of augmented indium oxide coatings are 
decisively influenced by the process used for application. Known are the 
vacuum processes, which generally require high investments. Also familiar 
are spray and CVD-processes, which however use much material that is not 
transformed into the coating and has to be reprocessed in an expensive 
process, particularly in the case of the expensive indium. For cadmium, 
the toxicity problem is considerable. The dipping process does not have 
these disadvantages and is therefore preferable. In the case of 
tin-augmented indium oxide, however, it has the same disadvantage as the 
other processes in that it requires a special, reducing gas atmosphere at 
high temperatures during or after the application process in order to 
obtain optimum electrical and optical properties. This frequently leads to 
the need for non-catalytic wall materials in order to prevent proportional 
H.sub.2 -combustions from the reducing gas. Moreover, it is necessary to 
have gas-tight furnaces operating at high temperatures. 
A further disadvantage of the process according to the state-of-the-art is 
that the augmented indium oxide layers cannot be applied directly to a 
desirable substrate, in particular not to the most interesting substrate, 
namely float glass containing alkali, since according to the 
state-of-the-art the Na.sup.+ ions which diffuse into the indium oxide 
coating reduce the conductivity of indium oxide coatings to an 
unacceptable degree. 
The object of the present invention is therefore a process which does not 
have the disadvantages of the known processes. This objective is 
accomplished by the process described in the patent claims. 
DISCLOSURE OF THE INVENTION 
Accordingly, it is a general object of the present invention to provide an 
improved process for economically preparing transparent, electrically 
conductive indium oxide coatings having improved properties. 
Another object of the present invention is to provide indium oxide coatings 
and articles of manufacture containing such coatings with augmented 
physical and electrical properties. 
A further object of the present invention is to provide improved cermet 
coatings and compositions. 
An additional object of the present invention is to provide improved gas 
sensors having essentially unchanged electrical properties over a varying 
response selectivity temperature range. 
A more particular object of the present invention is to provide augmented 
indium oxide coatings which can be directly applied to alkali-containing 
substrates such as glass without the need for an alkali barrier layer 
between coating and substrate. 
Upon study of the specification and appended claims, further objects, 
features and advantages of the present invention will become more fully 
apparent to those skilled in the art to which this invention pertains. 
BEST MODE FOR CARRYING OUT THE INVENTION 
Briefly, the above and other objects, features and advantages of the 
present invention are attained in one aspect thereof by providing a 
process for the production of transparent, electrically conductive indium 
oxide coatings by dipping a substrate capable of being coated with indium 
oxide into a solution containing a hydrolyzable indium compound capable of 
forming said coating, removing excess solution from the coated substrate, 
then drying and tempering the resultant substrate, wherein the dipping 
solution additionally contains an effective amount of at least one 
hydrolyzable compound which is capable of augmenting the electrical 
properties of the resultant coating in comparison with indium oxide alone 
and which contains an element in the 2nd, 4th or 5th main group, or in the 
1st, 2nd, 4th, 5th or 8th subgroup of the Deming Periodic System of 
elements, or of the rare earth metals. 
Use is made of hydrolyzable compounds of indium combined with hydrolyzable 
compounds of the 2nd, 4th or 5th main group and the 1st, 2nd, 4th, 5th or 
8th subgroup or the rare earth elements, e.g., Ag, Au, Cu, Ca, Mg, La, Nb, 
Rh, Os, Ir, Ta, Pt, Hf, Hg, As, Bi, Sb, Zn, Cd, Y, Si, Ti, Zr, Pb, Ge, Co, 
Pd, Ce, Nd, Ni, Ru, V, Fe, in alcoholic solutions, and, if necessary, with 
the additions of chelate-forming agents, such as acetylacetone, 
acetoacetic acid ethyl ester, monocarboxylic acids, polycarboxylic acids, 
polyalcohols, such as glycol and glycerin, hydroxyketones, ketones, 
aldehydes, aliphatic and aromatic hydrocarbons, aliphatic and aromatic 
amines such as pyridine, alpha-picoline, triethylamine, ethanol amine, 
urea and urotropine. 
The hydrolyzable compounds are, e.g., alkoxides, nitrates, salts of organic 
acids, such as acetates, chelates, e.g., acetylacetonates, etc. 
The production of such solutions is simple and considerably less expensive 
than producing two- or several-component targets for a sputter process. 
Maintaining a desired composition or stoichiometry of the layer--again in 
contrast to the vacuum process--is simple and reliable even for systems 
with two and several components, probably because the reactive components 
already react while in solution or, at the latest, during formation of the 
coating. 
The substrate, e.g., a glass plate, is dipped in the familiar manner into 
such a solution, is withdrawn from it at a steady rate into an atmosphere 
of conditioned temperature and humidity, and finally is heated to 
400.degree.-500.degree. C. in the presence of air. Suitable substrates are 
all glasses, including particularly the alkali-containing float glasses, 
silica glasses, glass ceramics, mica, as well as metals, such as copper, 
iron, and others. 
The solutions employed according to the present invention have the 
advantage of providing excellent wetting of the substrates, which is even 
better than that of many of the familiar dipping solutions for coating 
glass. 
In the present invention cadmium-containing indium solutions have proved to 
be particularly advantageous, while simultaneosly allowing the CdO 
augmentation of In.sub.2 O.sub.3 -coatings to be varied by up to four 
orders of magnitude. 
When the additions are &gt;1 mol % of CdO relative to In.sub.2 O.sub.3, the 
coatings, even on alkali-containing float glass, achieve their full 
conductivity of &lt;500 Ohms/square when heated to 500.degree. C. in the 
presence of air. This is a surprising finding for dipped coatings because 
alkalies diffuse well at 500.degree. C. 
At low CdO-contents and with coatings produced at temperatures of below 
500.degree. C., conductivity can be further improved by a very simple 
reforming process. It is very simple and economical because it can be 
carried out in a forming gas atmosphere, which does not need to be set 
rigidly and does not need to be maintained at a constant value, and 
because it can be carried out at 200.degree.-350.degree. C. in simple 
furnaces, which need not be airtight. Compared to state-of-the-art 
techniques, gastight furnaces, as well as the transportation system in 
them and the special, non-catalytic wall materials, are eliminated. The 
reforming is particularly advantageous for thin glasses, e.g., of 0.5 mm, 
because they cannot readily be heated to 500.degree. C. without 
deformation. This type of glasses is used for displays, with the desired 
surface resistivities specifically lying in the area of 200-500 
Ohms/square as provided by the process of the invention. The layers 
produced in this manner can be etched with diluted hydrochloric acid, a 
requirement placed on display layers. 
In the past, In.sub.2 O.sub.3 -coatings augmented wtih CdO have been 
applied in a spraying process on hot glass plates; see R. Groth, Phys. 
Stat. Sol 14: 69 (1966). Such an In.sub.2 O.sub.3 -coating containing 1.5% 
of CdO has an electron concentration of 3.times.10.sup.19 cm.sup.-3 and a 
mobility of 6 cm.sup.2 V.sup.-1 s.sup.-1 and therefore is far inferior to 
the coatings of the invention, having values of 3.3.times.10.sup.20 
cm.sup.-3 and 16 cm.sup.2 V.sup.-1 s.sup.-1. Additionally, coatings 
produced in a spraying process do not have the required homogeneity; the 
loss of spraying material, which cannot be transformed into the coating, 
is uneconomical. For spraying processes the problems resulting from toxic 
Cd-compounds are considerable, but there are no problems with the dipping 
processes, since the solution does not dissipate into the air but only 
remains on the substrate. Vapour pressures are low for the Cd-compounds 
used; MAK-values (maximum working environment concentration) are 
maintained. 
In the sputter process of R. Groth, Phys. Stat. Sol 14: 69 (1966) coatings 
of CdO, having been augmented with 5 percent per atom of indium, were 
produced having a coating thickness of 281 nm, which have a mobility of 
2.3 cm.sup.2 V.sup.-1 s.sup.-1 and a specific electrical conductivity of 
189 Ohms.sup.-1 cm.sup.-1. This corresponds to a surface resistivity of 
188 Ohms/square, which by comparison is again inferior to the coatings of 
the present invention. 
The most recent citation in the literature, G. Haake, SPIE Vol. 324 Optical 
Coatings for Energy Efficiency and Solar Applications (1982, reports about 
CdIn.sub.2 O.sub.4 - coatings (RF Sputter Process) having a electrical 
conductivity of 3,000-4,000 Ohms.sup.-1 cm.sup.-1, which would be 
excellent values. The absence of additional data, such as charge carrier 
concentration, mobility, and coating thickness, prevents a more detailed 
comparison with the coatings of the present invention. Moreover, these 
CdIn.sub.2 O.sub.3 - coatings are described only for silica glass. 
In the process according to the present invention it is, among other 
things, surprising to find that coatings of good electrical conductivity 
form directly on glass containing alkali. This seems to be an as yet 
unexplainable characteristic of the coating composition of this invention, 
and can be observed especially for coatings of In.sub.2 O.sub.3 containing 
Cd. This represents a remarkable technological advance since until now 
alkali-containing glass, which has been used most frequently as a 
substrate, has always required that an alkali barrier layer, e.g., of 
SiO.sub.2, be applied first, due to alkali diffusion in the 
state-of-the-art processes. Elimination of the barrier layer represents a 
considerable economic advantage. 
The other augmentation substances also exhibit heretofore unobserved, 
specific properties. For example, indium oxide coatings which have been 
augmented with silver, gold, copper, palladium, ruthenium, rhodium and 
platinum, can be called cermet coatings. 
In this connection, a palladium-augmented indium oxide coating, if suitably 
installed, can be used as gas sensor, particularly for hydrogen, oxygen, 
nitrogen, alcohol, and water. The response selectivity of the coating 
depends on the temperature; e.g., the temperature of the layer should be 
120.degree.-150.degree. C. for oxygen measurements, whereas a temperature 
of 25.degree.-50.degree. C. is sufficient to measure ethanol 
concentrations in the atmosphere. A special advantage results from the 
fact that both sides are inevitably coated when coating by means of a 
dipping process. The top side, on which the contacts are located, 
functions proportionally better as a sensor, whereas the underside can 
serve to heat the substrate due to its suitable resistivity. When an 80 V 
voltage is applied, the current which flows is usually about 200-500 
milliampere, depending on the surface resistivity of the coating. It is 
sufficient to achieve a substrate temperature of 50.degree.-250.degree. C. 
In this temperature range the coating does not, for all practical 
purposes, change its properties, e.g., its surface resistivity. Among 
others, In.sub.2 O.sub.3 -coatings, which have been augmented with Cd, Pt, 
Rh, Ru, Zn and Ag, exhibit excellent sensor properties with the most 
varied gasses, such as saturated and unsaturated hydrocarbons, nitrogen 
oxides, sulfur dioxide, carbon monoxide, alcohols, hydrogen, and others. 
Indium oxide coatings augmented with titanium dioxide have a remarkable 
stability against concentrated acids. It is known that indium oxide and/or 
tin-augmented indium oxide coatings are relatively reasily soluble in 
acids. Indium oxide coatings augmented with titanium dioxide, however, do 
not dissolve, even after being exposed to diluted or concentrated acids, 
such as hydrochloric acid, nitric acid, and sulfuric acid, for hours. This 
type of coating represents ideal, transparent, electrically conductive 
electrodes for applications in chemically aggressive media. 
Layers which have been augmented with calcium are characterized by special 
hardness. 
Without further elaboration, it is believed that one skilled in the art 
can, using the preceding description, utilize the present invention to its 
fullest extent. The following preferred specific embodiments are, 
therefore, to be construed as merely illustrative and not limitative of 
the remainder of the disclosure in any way whatsoever. In the following 
Examples, the temperatures are set forth uncorrected in degrees Celsius; 
unless otherwise indicated, all parts and percentages are by weight.

COMATIVE EXAMPLE 
Indium Oxide Dipping Solution and Coating 
26.5 g Indium-III-nitrate are dissolved in a mixture of 16 ml water and 14 
ml acetic acid and are diluted with 200 ml of ethanol. 
A borosilicate glass plate (Tempax.TM.) is dipped into the indium oxide 
dipping solution and is then withdrawn from the solution at a constant 
speed (of 0.6 cm per second). The plate is briefly pre-dried at 
250.degree. C., is then heated to 400.degree. C. in an nitrogen/hydrogen 
atmosphere, and then suddenly cooled again. 
In the following Examples, the indium oxide component of the dipping 
solution is an aqueous acidic solution of an inorganic indium salt diluted 
with an excess of alcohol. 
A layer produced in this manner has the following properties: 
Layer thickness: 61 nm 
Surface resistivity: 432 Ohms/square 
Electrical conductivity: 379 cm.sup.-1 
Charge carrier concentration: 7.5.times.10.sup.19 cm.sup.-3 
Mobility: 31 cm.sup.2 V.sup.-1 s.sup.-1. 
EXAMPLE 1 
Indium Oxide Coating Augmented With Cadmium Oxide 
An indium oxide dipping solution produced as described in the comparative 
example is supplemented with 5 g cadmium acetate (Cd(OOCCH.sub.3).sub.2 
.times.2 H.sub.2 O), while stirring, and is diluted further with 40 ml of 
ethanol. 
A 2 mm thick float glass plate is dipped into the dipping solution and is 
withdrawn at a constant speed. After drying for 2 minutes at 250.degree. 
C. the coated plate is heated to 500.degree. C. in the presence of air, 
and is maintained at this temperature for 5 minutes. After cooling, the 
coating has the following properties: 
Coating thickness: 60 nm 
Surface resistivity: 194 Ohms/square 
Electrical conductivity: 830 Ohms.sup.-1 cm.sup.-1 
Mobility: 16 cm.sup.2 V.sup.-1 s.sup.-1 
Charge carrier concentration: 3.3.times.10.sup.20 cm.sup.-3 
Transmission (550 nm): ca. 80% 
Reflection (550 nm): ca. 17% 
EXAMPLE 2 
Indium Oxide Coating Augmented With 
Cadmium Oxide With Subsequent Reforming 
A thin glass plate of 0.7 mm thickness is dipped into a dipping solution 
produced as described in Example 1, and is withdrawn at a constant speed. 
After pre-drying for 2 minutes at 250.degree. C., the coated plate is 
heated to 430.degree. C. in the presence of air and is then cooled to room 
temperature. Subsequently, the coated glass plate is reheated at 
250.degree. C. for 5 to 10 minutes in a forming gas atmosphere comprising 
essentially about 10 Vol. % hydrogen, about 90 Vol. % nitrogen, &lt;1% oxygen 
and &lt;0.1% water. Surface resistivity is about 800-1,200 Ohms/square prior 
to forming; afterward, the coat has a surface resistivity of 200-300 
Ohms/square. 
EXAMPLE 3 
Indium Oxide Coating Augmented With 
A Small Amount Of Cadmium Oxide 
An indium oxide dipping solution produced as described in the comparative 
example is supplemented with 1.5 g cadmium acetate (Cd(OOCCH.sub.3).sub.2 
.times.2H.sub.2 O) while the solution is being stirred. 
The coating is produced as described under Example 1. The surface 
resistivity of such a coating is &gt;500 KOhms. If such a coating is heated 
to 400.degree. C. in a forming gas atmosphere, and is then suddenly 
cooled, it will have a surface resistivity of 450 Ohms/square. 
EXAMPLE 4 
Indium Oxide Coating Augmented With Zinc Oxide 
5.7 g zinc nitrate (Zn(NO.sub.3).sub.2 .times.4H.sub.2 O) are dissolved by 
stirring into an indium oxide dipping solution produced as described in 
the comparative example, whereupon the solution is diluted with 250 ml of 
ethanol. 
A borosilicate glass plate is dipped into the dipping solution produced and 
is withdrawn at a constant speed. After drying at 250.degree. C. for 5 
minutes, the coated plate is heated to 450.degree. C. in the presence of 
air and is cooled at once. The sample is then tempered in a forming gas 
atmosphere at 350.degree. C. for 10 minutes. A coating produced in this 
manner has the following properties: 
Layer thickness: 90 nm 
Surface resistivity: 343 Ohms/square 
Charge carrier concentration: 1.6.times.10.sup.20 cm.sup.-3 
Mobility: 13 cm.sup.2 V.sup.-1 s.sup.-1 
Electrical conductivity: 330 Ohms.sup.-1 cm.sup.-1. 
EXAMPLE 5 
Indium Oxide Coating Augmented With Palladium 
1 g of palladium(II)-acetylacetonate is dissolved, while stirring, into an 
indium oxide dipping solution produced as described in the comparative 
example. 
A borosilicate glass plate is dipped into the dipping solution and is 
withdrawn at a constant speed. The sample is heated to 500.degree. C. in 
the presence of air and is suddenly cooled. The coating has a surface 
resistivity of 1.6 KOhms. After forming at 400.degree. C. for 5 minutes, 
the layer has a surface resistivity of 300 Ohms/square. 
EXAMPLE 6 
Indium Oxide Coating Augmented With Titanium Dioxide 
An indium oxide dipping solution produced as described in the comparative 
example is supplemented with 9 g of titanium tetraethylate dissolved in 30 
ml of ethanol and 20 ml of acetic acid. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried for 10 minutes at 
250.degree. C. and is tempered for 10 minutes at 500.degree. C. in the 
presence of air. This type of layer has a surface resistivity of about 2 
MOhms/ square. After tempering in a forming gas atmosphere for 15 minutes 
at 450.degree. C., the layer has a surface resistivity of 630 Ohms/square. 
This layer has very good stability against concentrated acids and bases. 
EXAMPLE 7 
Indium Oxide Coating Augmented With Zirconium Dioxide 
An indium oxide dipping solution produced as described in the comparative 
example is supplemented with 5 g zirconium tetrabutylate dissolved in 5ml 
of acetic acid and 20 ml of ethanol. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried at 250.degree. C. 
for 2 minutes, is heated to 500.degree. C. and is suddenly cooled. This 
type of layer has a surface resistivity of &gt;5 MOhms. After heating to 
400.degree. C. in a forming gas atmosphere and sudden cooling, this type 
of layer has a surface resistivity of 50 Ohms/square. 
EXAMPLE 8 
Indium Oxide Coating Solution Augmented With Magnesium Oxide 
An indium oxide dipping solution produced as described in the comparative 
example is supplemented with 1.3 g magnesium nitrate (Mg(No.sub.3).sub.2 
.times.2H.sub.2 O) and is diluted with 50 ml ethanol. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried at 250.degree. C. 
for 5 minutes and is tempered in a forming gas atmosphere for 15 minutes 
at 500.degree. C. A coating produced in this manner has a surface 
resistivity of 2.2 KOhms/square. 
EXAMPLE 9 
Indium Oxide Coating Augmented With Calcium Oxide 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 1.4 g calcium nitrate (Ca(NO.sub.3).sub.2 
.times.2H.sub.2 O) and 100 ml ethanol. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The layer is dried at 250.degree. C. for 
5 minutes and is then tempered in a forming gas atmosphere at 500.degree. 
C. for 45 minutes. A coating produced in this manner has a surface 
resistivity of 10-15 KOhms/square. The coatings of indium oxide augmented 
with calcium oxide are characterized by an exceptional coating hardness. 
EXAMPLE 10 
Indium Oxide Coating Augmented With Silver 
A dipping solution produced as described in the comparative example is 
supplemented with 0.5 g silver nitrate. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried for 5 minutes at 
250.degree. C. and is heated to 450.degree. C. in the presence of air. 
After cooling, the coating is tempered in a forming gas atmosphere at 
400.degree. C. The coating has a surface resistivity of 3,000 Ohms/square. 
EXAMPLE 11 
Indium Oxide Coating Augmented With Neodymium Oxide 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 3.9 g neodymium(III) acetylacetonate and 
diluted with 50 ml of ethanol. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried at 250.degree. C. 
for 5 minutes, and is then heated to 400.degree. C. in a forming gas 
atmosphere. After cooling, this type of layer has a surface resistivity of 
530 Ohms/square. 
EXAMPLE 12 
Indium Oxide Coating Augmented With Cadmium Oxide And Zinc Oxide 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 19.5 g cadmium acetate (Cd(OOCCH.sub.3).sub.2 
.times.2H.sub.2 O) and 19.1 g zinc nitrate (Zn(NO.sub.3).sub.2 x 4H.sub.2 
O) dissolved in 23 ml acetic acid and 22 ml water, and is then diluted 
with 150 ml of ethanol. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is heated to 500.degree. C. 
in the presence of air. A coating produced in this manner has a surface 
resistivity of 800 Ohms/square. 
EXAMPLE 13 
Indium Oxide Coating Augmented With Gold 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 1.7 g of gold (III) chloride and 0.5 g of 
citric acid. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried at 250.degree. C. 
for 5 minutes and is tempered in a forming gas atmosphere at 450.degree. 
C. for 10 minutes. This type of layer has a surface resistivity of 2,100 
Ohms/square. 
EXAMPLE 14 
Indium Oxide Coating Augmented With Lead Oxide 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 6 g of lead (II) acetate 
Pb(COOCH.sub.3).sub.2 .times.2H.sub.2 O), dissolved in a 20 ml of glycol, 
and diluted with 150 ml of ethanol. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried at 250.degree. C. 
for 5 minutes and tempered in a forming gas atmosphere at 400.degree. C. 
for 5 minutes. A coating produced in this manner has a surface resistivity 
of 1,800 Ohms/square. 
EXAMPLE 15 
Indium Oxide Coating Augmented With Cobalt Oxide 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 1.1 g cobalt (II) nitrate (Co(NO.sub.3).sub.2 
.times.4H.sub.2 O). 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is died for 10 minutes at 
250.degree. C. and is tempered at 500.degree. C. for 10 minutes in a 
forming gas atmosphere. A coating of this type has a surface resistivity 
of 300 KOhms/square. 
EXAMPLE 16 
Indium Oxide Coating Augmented With Vanadium Oxide 
A dipping solution of indium oxide produced as described in the comparative 
example and is supplemented with 2.3 g of vanadium (IV) acetylacetonate 
and then with 0.5 ml of pyridine. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried at 250.degree. C. 
for 10 minutes and is then tempered at 500.degree. C. for 10 minutes in a 
forming gas atmosphere. A coating of this type has a surface resistivity 
of 15 KOhms/square. 
EXAMPLE 17 
Indium Oxide Coating Augmented With Antimony Oxide 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 2.4 g of antimony (III) chloride dissolved in 
10 ml of acetoacetic acid ethylester. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried at 250.degree. C. 
for 10 minutes and is tempered at 500.degree. C. for 10 minutes in a 
forming gas atmosphere. A layer of this type has a surface resistivity of 
4.6 KOhms/square. 
EXAMPLE 18 
Indium Oxide Coating Augmented With Ruthenium 
A dipping solution of indium oxide produced as described in the comparative 
example is supplemented with 1.0 g of ruthenium (III) chloride. 
A borosilicate glass plate is slowly dipped into the dipping solution and 
is withdrawn at a constant speed. The coating is dried for 10 minutes at 
250.degree. C. and tempered in a forming gas atmosphere at 400.degree. C. 
for 10 minutes. A coating produced in this manner has a surface 
resistivity of 420 Ohms/square. 
The preceding examples can be repeated with similar success by substituting 
the generically or specifically described reactants and/or operating 
conditions of this invention for those specifically used in the examples. 
From the foregoing description, one skilled in the art to which this 
invention pertains can easily ascertain the essential characteristics 
thereof and, without departing from the spirit and scope of the present 
invention, can make various changes and modifications to adapt it to 
various usages and conditions. 
Industrial Applicability 
As can be seen from the present specification and examples, the present 
invention is industrially useful in providing an economical method for 
producing transparent, electrically conductive, augmented indium oxide 
coatings which are used in a wide variety of applications, e.g. heat 
reflection, optical displays, heating or sensor layers, etc.