JP3043826B2 - Varistor ink composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composition for varistors.

[0002]

2. Description of the Related Art A zinc oxide varistor is a ceramic semiconductor device containing zinc oxide as a main component. They have high non-linear current / voltage characteristics similar to a return load zener diode, but have extremely large current and energy handling capabilities. The varistor is manufactured by a ceramic sintering method that results in a structure (texture) consisting of conductive zinc oxide particles surrounded by an electrically insulating barrier. These barriers contribute to trapping states at grain boundaries induced by additional elements such as bismuth, cobalt, praseodymium, manganese, and the like.

[0003] The electrical performance of metal oxide varistors made from metal oxides is related to device size. Each zinc oxide grain of the ceramic acts as if it had a semiconductor junction at the grain boundary. Non-linear electrical behavior occurs at the grain boundaries of each semiconductor zinc oxide grain. Thus, a varistor can be thought of as a multiple junction device consisting of many series and parallel connections of grain boundaries. The behavior of the device is analyzed for details of the ceramic microstructure (structure). Average particle size and particle size distribution play a major role in the electrical behavior.

[0004] The manufacture of zinc oxide varistors has traditionally followed standard ceramic technology. After mixing the zinc oxide and other ingredients, for example by milling in a ball mill,
Spray dry. The mixed powder is then pressed into the required shape, typically tablets or pellets. The resulting tablets or pellets are hot, typically 1000 ° C
Sinter at １1400 ° C. The sintered device then provides the electrodes, typically using sintered silver contacts. The behavior of the device does not depend on the configuration or basic composition of the electrode. Next, lead wires are attached with solder. The final device is then encapsulated with a polymeric material to meet specific mounting and performance requirements.

[0005] The majority of the varistors between the contact or electrode layers in the device thus produced are mainly composed of zinc oxide particles of a predetermined average particle size, giving a specific resistivity per unit thickness. When designing a varistor at a constant nominal voltage, and thus having an appropriate number of grains in series between the electrodes, is basically a matter of device thickness selection. The voltage gradient of the varistor material with respect to voltage per unit thickness can be controlled by changing the varistor composition and manufacturing conditions. The particle size can be changed by changing the composition of the additive which is a metal oxide. In practice, the voltage drop per grain boundary junction is nearly constant and does not vary much with grain size. Therefore, the voltage of the varistor is mainly determined by the thickness of the material and the size of the grains.

The construction and performance of varistors is described in Levinson et al. (“Zinc Oxide Varistors-A Review” by LM Levi
nson and HR Philipp, Ceramic Bulletin, Vol. 65, N
o.4 (1966)).

A number of specific varistor compositions are known, and are disclosed, among others, in the following patent specifications: US Pat. Nos. 3,598,763; 3,663,458; 3,863,193;
4,045,374 and British Patent 1,478,772. The method of manufacturing varistors is described in particular in U.S. Pat. Nos. 3,863,193 and 4,
No. 148,135.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an excellent composition of materials used in the manufacture of varistors. It is a further object of the present invention to provide a suspension of a zinc oxide-based material in a solvent for use in manufacturing varistors using a wet screen coating method.

In particular, the present invention relates to compositions that facilitate the manufacture of multilayer varistors. Although multilayer varistors have been found to have a number of advantages over comparable radial products, manufacturing issues have heretofore hindered the widespread use of multilayer varistors.

One advantage of the multilayer structure is that it has a compact size for the same electrical properties as compared to conventional radial devices. Also, the multi-layer varistor is completely symmetric, completely inactivated and has a good IV
Has characteristics. Possible disadvantages for this are that it involves a relatively high capacitance and potential reaction between the ceramic and the internal electrode, especially the interaction of the palladium and bismuth composite.

[0011] The invention further relates to a composition for use in the production of multilayer varistors by the printing method. A method of manufacturing a multilayer varistor by a series of printing steps is the subject of a co-pending patent application by the present applicant. In the particular manufacturing method disclosed in the co-pending application, both the ceramic layer and the electrode pattern are screen printed sequentially. An advantage of the screen printing method over other manufacturing methods for multilayer systems is that the direct application of the ceramic material and electrode pattern in a continuous printing process can eliminate the preparation of thin sheet material as a preliminary step. Thus, the screen coating method provides a more convenient and faster method of manufacturing multi-layer products, especially varistors, than methods that include a preliminary step of manufacturing sheets or panels of ceramic and electrode materials for interleaving in subsequent manufacturing steps. . However, the successful implementation of multilayer varistor printing manufacturing techniques requires providing a composition that is compatible with this manufacturing method and that can work with the solvent material to provide the required ceramic and electrode inks.

Accordingly, it is a specific object of the present invention to provide an ink suitable for screen coating manufacturing techniques for multilayer varistors. Powder compositions suitable for incorporation into such inks are the subject of the applicant's co-pending application.

[0013]

According to the present invention, there is provided a ceramic structure selected from the group consisting of (a) zinc oxide; (b) at least bismuth oxide or boric acid, chromium oxide, cobalt oxide, manganese oxide and tin oxide. (C) at least one additive affecting grain growth selected from the group consisting of at least antimony oxide, silicon dioxide and titanium dioxide; (d) an organic solvent carrier; (e) viscosity. A composition material for use in the manufacture of a varistor is provided, comprising:

[0014] The additives that affect the structure (structure) of the ceramic of the vapor include at least bismuth oxide, cobalt oxide and manganese oxide. The composition material comprises at least one additive that affects electrical performance selected from the group consisting of at least one aluminum nitrate and silver oxide. The composition material also contains nickel oxide and magnesium hydroxide as further additives.

Further, according to the present invention, (a) zinc oxide 94-
(C) a plurality of additives from at least bismuth oxide, boric acid, chromium oxide, cobalt oxide, manganese oxide and tin oxide, which affect the structure of the ceramic; At least one additive that affects grain growth selected from the group consisting of at least antimony oxide, silicon dioxide and titanium dioxide; 0.1-1.6 mol%; (d) an organic solvent carrier;
(e) A composition material for use in the manufacture of varistors is provided, comprising: an organic additive affecting viscosity; and an organic binder.

The composition material comprises at least one additive selected from the group consisting of at least one aluminum nitrate and silver oxide that affects electrical performance.
It can consist of mole%. Also, the composition material may comprise 0.6-1.1 mol% of nickel oxide as a further additive and at least 0.4 mol% of magnesium oxide as a further additive.

The inorganic component of the composition material is desirably granular or powdery, and the average particle size of the granular or powdery material is desirably about 2 microns or less.

Suitably, the relative proportions of the organic components are chosen such that the mixture of organic and inorganic components of the composition is in the form of a suspension.

The present invention also provides a printing ink comprising the above composition material and a method for producing a composition material used for producing a varistor comprising the following steps: (a) (a) zinc oxide, (b) at least One or more additives affecting the ceramic structure selected from the group consisting of bismuth oxide, boron oxide, chromium oxide, cobalt oxide, manganese oxide and tin oxide; and (c) at least from antimony oxide, silicon dioxide and titanium dioxide. Calcining a granular or powdery composition material comprising at least one additive affecting grain growth selected from the group consisting of:
And (b) mixing the calcined composition with an organic solvent carrier, an organic additive that affects viscosity, and an organic binder.

The above additives are added in the first stage of the mixing process, the binder is added after the first stage of the mixing process, and the binder is mixed with other material components in the second stage of the mixing process. Is desirable. Preferably, the first stage of the mixing process comprises a grinding process.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, zinc oxide powder and additives are weighed prior to mixing into a powder mixture suitable for making the particular varistor required. The powder mixture is then mixed with a suitable organic component to provide a ceramic ink. A suitable screen is prepared, a ceramic layer is deposited on the substrate by screen printing, and an interleaving operation cycle is performed.
An electrode layer is likewise screened over the semi-dry layer of ceramic material.

After completion of the screen lamination, the printed layered product supported on the substrate is separated to provide a number of multilayer varistor units. Subsequent processing steps are generally conventional, burning out binders and organic components, then firing and grinding the product and adding terminations for electrical connection between the varistor and other circuit elements After that, the final varistor is tested. Optional final steps include lead attachment and overall encapsulation.

The applicant's co-pending patent application (Title of Invention: Varistor Structure, Varistor Shape and Varistor Manufacturing Method and Apparatus) is a multi-layer varistor manufacturing method and a multi-layer varistor manufacturing method. The details of the configuration of the varistor are disclosed. The present invention provides novel compositions suitable for use in the method and in the manufacture of multilayer varistors.

Table 1 below shows the materials present in the ceramic powder composition for the production of varistor powder mixtures, in particular multilayer varistors:

[0025] Table 1 materials Formula zinc oxide ZnO bismuth oxide Bi ₂ O ₃ cobalt oxide CO ₂ O ₃ manganese oxide MnO ₂ nickel oxide NiO antimony oxide Sb ₂ O _3, silicon dioxide SiO ₂ Magnesium hydroxide Mg (OH) ₂ → MgO aluminum nitrate _{Al 2 (NO 3) 3 ·} 9H 2 O was added as the Al ₂ O ₃ chromium oxide Cr ₂ O ₃ barium carbonate BaCO ₃ → BaO borate HBO ₃ titanium dioxide TiO ₂ of tin oxide SnO ₂ silver oxide Ag ₂ O

The various materials listed in Table 1 can be classified as follows: Zinc oxide: Zinc oxide typically comprises 85-95 mol%, for example 92 mol%, of the varistor mixture mass. For low voltage varistors, barium particles are added in the form of barium carbonate, which is converted to barium oxide during the manufacturing process. The action of barium promotes the growth of zinc oxide grains. And this additive disappears after sintering of the varistor. 2. Materials related to glass (additives that influence the structure of the ceramic) These additives act to promote the growth of the ceramic structure. It contains the following materials shown in Table 1: Bismuth oxide added in the form of trioxide. This is a glass forming additive. Cobalt oxide is another glass additive that helps the glass frit and maintain phase stability in the ceramic. Manganese oxide has a similar increasing effect as bismuth oxide. Chromium oxide is yet another glass additive that acts to stabilize the ceramic product. Boric acid is another glass former. Tin oxide is yet another stabilizer for the glass structure, but is generally less used than previously cited. 3. Grain growth regulator (additive that affects grain growth) Antimony oxide is an additive that regulates grain growth and acts as an inhibitor that keeps the grain size small. This is especially important in high voltage devices. Silicon dioxide is a strong inhibitor of grain growth and is added to the composition or powder mixture to increase the voltage per unit thickness (mm). However, silicon dioxide itself is highly conductive,
It absorbs energy when the junction in the depletion layer breaks and conducts. The grain structure in the varistor is almost completely zinc oxide and the additives enter the glass matrix surrounding the grains. It is due to this configuration of the varistor that it has a significant effect on the performance of the device, as exemplified by the action of the conductive silicon dioxide at the grain boundaries. The remaining additive affecting grain growth shown in Table 1 is titanium dioxide. 4. Nickel dioxide Nickel oxide is a unique additive that has properties that cannot be obtained with other additive materials, and is aimed at stabilizing the microstructure. Nickel oxide helps to form microstructures in ceramic materials suitable for handling DC and AC stress. 5. Joining related additives (additives affecting electrical performance) Aluminum nitrate is an important additive in this category. This nitrate is converted to an oxide during the manufacturing process. As with most other additives, the aluminum oxide enters the glass matrix surrounding the grains. A very small amount (ppm) of aluminum oxide enhances the conductivity of zinc oxide. However, aluminum oxide at high additive levels can diffuse into the grain boundaries and reduce the interactivity of the grains, thereby providing a leaky device. Conversion of nitrate occurs during sintering. Silver oxide is
The varistor gives a few desirable results in combination with the aluminum additive in various mixtures. 6. Other Additives Magnesium hydroxide, which is converted to magnesium oxide in the final product, falls into this category. The function and action of this additive is unknown, and the properties that contribute to the performance of the varistor device are not fully understood. However, it is a traditional additive in radial varistors.

The classification of the materials that make up the powder mixture for varistor products described above is only one way to consider the purpose and function of each of the various materials and additives that make up the product. However, the specific analysis presented is useful in demonstrating the performance characteristics of varistor devices, especially the multilayer structure of such devices, and is a useful new mixture, especially ceramic inks for the production of screenless varistors. It has been found to be beneficial in the development and preparation of mixtures (compositions) suitable for use in The value of this classification is to assist in understanding certain aspects of the performance of the varistors, as well as to assist in the development of mixtures suitable for varistors, especially those manufactured by the screened method.

Table 2 shows a number of powder mixtures which have been found to be particularly suitable for the preparation of ceramic inks for use in the production of multilayer varistors by the screen sliver method. The amounts of the main components zinc oxide and additives of each category are given in mol% for each of the mixtures shown in the table. The desirable physical characteristics of the indicated powder mixture will be confirmed later when considering the preparation of the ceramic ink. However, Table 2
It is noted from Table 1 that the additives are present in different amounts depending on the mixture. The exact amount of additive selected in each category depends on the required purpose and performance of the varistor. For example, silicon dioxide is a stronger grain growth inhibitor than antimony oxide. However, the use of a large amount of silicon tends to lower the resistance of the grain boundary of the zinc oxide structure. To avoid possible problems associated with the use of high amounts of silicon, substitute different compositions with different balance of additives, depending on the required properties and performance of the final device, e.g. in terms of product life. Can be. The balance of functions and the interrelationship between the various additives is also complex and not completely understood. In order to obtain the required performance from the varistor product, for example, the glass face of the composition needs to be reconditioned, and it is not necessary to change only the grain growth regulator, for example, silicon dioxide. A variety of materials and additives react and work together in a complex manner so that the adverse effects of increased silicon levels can be offset, for example, by improving the ceramic glass structure. Therefore, the development of an effective and advantageous composition is a somewhat empirical technique, guided by theoretical considerations derived from the known properties of each material and additive of the composition.

[0029] Table 2 mixture materials 1 2 3 4 5 mol mol mol mol mol%%%%% main component zinc oxide 96.9 94.9 96.3 97.3 97.2 Additives that glass relationship 2.1 2.5 3.2 1.7 1.6 bismuth borate chromium oxide cobalt oxide Manganese oxide Selective crystal growth regulator from tin oxide 1.0 1.5 0.5 0.5 0.2 Antimony oxide Silicon oxide Titanium dioxide Selective bonding related additive 0.005 0.005 0.003 0.004 0.009 Aluminum nitrate Silver oxide Nickel oxide Nickel oxide-0.7-0.5 1.0 Magnesium hydroxide − 0.5 − − −

In all of the mixtures shown in Table 2, mol% is for dry product.

For use as an ink, it is necessary to suspend the ceramic powder mixture in a suitable solvent and to make the resulting ink product thixotropic (ie, the viscosity varies depending on the shear rate). Thixolotopy products typically behave like a very thick or sticky medium when the rate of shear is low, but can flow like a low viscosity liquid under high shear rates. To achieve this, a combination of organic materials is used as a solvent and carrier, with a desired range of particle sizes for the dry powder product.

Typically, a preferred particle size is about 1.5μ. The varistor powder obtained during the powder pre-production stage generally has a rather small particle size, e.g. Also, the range of particle sizes is generally relatively wide and the powder is not completely uniform. To make this dry powder suitable for mixing with varistor ceramic ink,
The particle size must be large to make the powder uniform. This is achieved by calcination. This calcination step is not usually necessary for most conventional powders for radial varistors, but is often used for multilayer varistors. The calcination step consists in firing the purchased powder at a temperature between 800C and 920C. The next calcined powder is then reduced in a grinding process.

Next, an organic solvent is added to the calcined powder to produce a thixotropic ceramic ink. These organic solvents include butyl acetate dioxitol or terpene alcohol. The organic material acts as a carrier for the suspended particles. Materials that affect viscosity are added with the main solvent additives to control the rheology of the ceramic ink.

A ceramic ink, which is typically green, is prepared from the above ingredients as described below. The calcined powder is mixed with the solvent and viscosity modifier by ball milling or other milling techniques. The proportions or amounts of these components are shown in Table 3. After milling, further organic products are added to obtain the required ink properties and fulfill the function of the binder. The binder can be ethylcellulose, ethylhydroxycellulose or a rosin derivative. The binder has a significant effect on the viscosity of the organic and ceramic powder mixture. For this, it is added to the mixture after the grinding step. If all of the binder required to obtain the thixotropic properties of the final ink is added before milling, the viscosity of the mixture will increase excessively and impair the milling operation.

Thus, in summary, considering the overall method of preparing powders and inks, a starting point is typically a powder having a particle size of 0.25 μm or less. After calcining, it is pulverized into particles having an average particle size of 2.0 μm. Next, a certain proportion of solvent is added to the large particle size product. Next, ball milling of the organic material and the ceramic powder product is performed. During this step the particle size again becomes slightly smaller, averaging about 1.
6 μ ± 10%. This level of particle size allows the powder to remain suspended in the ink product for a relatively long time.
Particle size is quite important in providing a satisfactory ceramic ink. If the particle size is too small, an excess of solvent will be required and it will be difficult to maintain a homogeneous suspension. On the other hand, if the particle size is too large, the particles settle under the influence of gravity, so that the powder particles are separated from the organic solvent material and the binder.

Table 3 below shows the weight percent of powder and organic components along with the zirconia cylinder weight required for ball milling to provide the specified amount of ceramic ink. The limits for the amounts of organic components shown in this table are typically ±
1%.

Table 3 Volume of ink (callon) 3.0 2.5 2.0 1.5 1.0 0.5 l (liter) 11.4 9.5 7.6 5.7 3.8 1.9 Calcined powder (g) 5635 4695.8 3756.7 2817.5 1878.3 939 Solvent (g) 1980 1650 1320 990 660 330 Viscosity Modifier (g) 38 31.7 25.3 19 12.7 6.4 Zirconia cylinder (g) 16000 13300 10600 8000 5300 2700

The solvents, viscosity modifiers and binders used in the ceramic inks of the present invention are natural materials and are advantageous in terms of safety with low toxicity and high flash point. Alternative materials meeting the same criteria are not readily available in place of these suitable solvents, but they are within the scope of the present invention.

As shown in Table 3, in the detailed preparation of the ceramic ink according to the above use, the required amounts of the various components are carefully weighed into a ball mill. The ball mill is preferably rotated at a speed of 36 to 42 rpm for about 24 hours. During a further mixing step following the ball milling step, a binder is added to the ceramic ink. The mixed product is then stored in a sealed container so that no volatile organic material is lost. After the above shear mixing, the ink must remain in sealed storage for at least 24 hours. The viscosity is then measured to determine its properties and stability required for printing.

The viscosity is measured with a suitable viscometer, for example, a Haake viscometer. This draws a relationship curve between shear stress and shear rate for a particular ceramic ink sample.
The plot desirably comprises the necessary relationship or standard curve between shear stress and shear rate, using which the numerical value of the sample must fall within certain predetermined limits. If the shear stress performance of the sample differs from the value of the standard curve, the ink is reprocessed to adjust its viscosity. The standard curve also allows the viscosity to change during shelf storage of the ceramic ink prior to using the ceramic ink for printing.

The organic material contained in the ceramic ink serves only to flow and apply the ink in the manufacture of the multilayer ceramic varistor product. During the subsequent firing of the formed product, all the organic material evaporates, leaving behind only the ceramic powder in the sintered structure along with the interleaving layer of the electrode material.

While various embodiments of the present invention have been described above for purposes of illustration, they are not meant to be limiting. It will be apparent to those skilled in the art that variations and modifications may be made to the embodiments of the present invention without departing from the scope and spirit of the claims.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a series of steps for manufacturing a multilayer varistor.

FIG. 2 is a diagram showing a relationship curve between shear stress and shear rate of a ceramic ink according to the present invention.

Continued on the front page (72) Inventor Derek A. Nicker, UK, Norfolk N. 319 N.S., Great Yarmouth, Belton, St. John's Road 24 (72) Inventor John M. Shreve, UK, Norfolk N.R. , Norwich, Flemingham R, St. Anne's Road 32 (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01C ^7/ 02-7/22

Claims (41)

(57) [Claims] A zinc oxide; a plurality of additives that affect the structure of a ceramic selected from the group consisting of at least one of bismuth oxide, boric acid, chromium oxide, cobalt oxide, manganese oxide, and tin oxide; At least one additive that affects grain growth selected from the group consisting of silicon dioxide and titanium dioxide; an organic solvent carrier; an organic additive that affects viscosity; and an organic binder. Composition material for varistor production. 2. The composition material according to claim 1, wherein the plurality of additives affecting the structure of the ceramic include at least bismuth oxide, cobalt oxide and manganese oxide. 3. The composition material according to claim 1, further comprising an additive that affects electrical performance selected from the group consisting of aluminum nitrate and silver oxide. 4. The composition of claim 2 further comprising at least one additive affecting electrical performance selected from the group consisting of aluminum nitrate and silver oxide. 5. The composition according to claim 1, further comprising nickel oxide as another additive. 6. The composition material according to claim 2, further comprising nickel oxide as another additive. 7. The composition material according to claim 3, further comprising nickel oxide as another additive. 8. The composition of claim 1, further comprising magnesium hydroxide as another additive. 9. The composition according to claim 2, further comprising magnesium hydroxide as another additive. 10. The composition according to claim 3, further comprising magnesium hydroxide as another additive. 11. The composition of claim 4, further comprising magnesium hydroxide as another additive. 12. A composition comprising: 94 to 98 mol% of zinc oxide; at least one additive which affects the structure of a ceramic selected from the group consisting of at least bismuth oxide, boron oxide, chromium oxide, cobalt oxide, manganese oxide and tin oxide. 4 mol%; at least 0.1 to 1.6 mol% of at least one additive affecting grain growth selected from the group consisting of antimony oxide, silicon dioxide and titanium dioxide;
Organic solvent carriers; organic additives affecting viscosity;
And an organic binder. 13. The composition material according to claim 12, further comprising 0.002 to 0.01 mol% of an additive that affects electric performance selected from the group consisting of aluminum nitrate and silver oxide. 14. The composition material according to claim 12, further comprising 0.6 to 1.1 mol% of nickel oxide as another additive. 15. The composition material according to claim 13, further comprising 0.6 to 1.1 mol% of nickel oxide as another additive. 16. The composition of claim 12, further comprising at least 0.4 mol% of magnesium hydroxide as another additive. 17. The composition of claim 13 further comprising at least 0.4 mol% of magnesium hydroxide as a further additive. 18. The composition of claim 14 further comprising at least 0.4 mol% of magnesium hydroxide as a further additive. 19. The composition of claim 1, wherein the inorganic constituent material is in particulate and powder form, and wherein the granular or powdered material has an average particle size of about 2 microns or less. 20. The composition of claim 3, wherein the inorganic constituent material is in particulate and powder form, and wherein the particulate or powdered material has an average particle size of about 2 microns or less. 21. The composition of claim 5, wherein the inorganic constituent material is granular and powdered, and the average particle size of the granular or powdered material is about 2 microns or less. 22. The composition of claim 8, wherein the inorganic constituent material is granular and powdered, and the average particle size of the granular or powdered material is about 2 microns or less. 23. The composition of claim 12, wherein the inorganic constituent material is granular and powdery, and wherein the granular or powdery material has an average particle size of about 2 microns or less. 24. The composition of claim 13, wherein the inorganic constituent material is granular and powdered, and the average particle size of the granular or powdered material is less than about 2 microns. 25. The composition of claim 14, wherein the inorganic constituent material is granular and powdered, and the average particle size of the particulate or powdered material is less than about 2 microns. 26. The composition of claim 1, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 27. The composition of claim 3, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 28. The composition of claim 5, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 29. The composition of claim 8, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 30. The composition of claim 12, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 31. The composition according to claim 13, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 32. The composition of claim 14, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 33. The composition of claim 15, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 34. The composition of claim 16, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 35. The composition of claim 17, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 36. The composition of claim 18, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 37. The composition of claim 19, wherein the relative proportions of the organic components are selected such that the mixture of the organic and inorganic components of the constituent material is in the form of a suspension. 38. (a) affecting the structure of a ceramic selected from the group consisting of (a) zinc oxide, (b) at least one of bismuth oxide, boron oxide, chromium oxide, cobalt oxide, manganese oxide and tin oxide; Calcining a particulate or powdered composition material comprising a plurality of additives and (c) at least one additive that affects grain growth selected from the group consisting of at least antimony oxide, silicon dioxide and titanium dioxide; And (b) mixing the calcined composition with an organic solvent carrier, an organic additive that affects viscosity, and an organic binder. 39. The method according to claim 39, wherein the additive is added to the first in the mixing step.
The method of claim 1 wherein the binder is added after the first stage of the mixing process and the binder is mixed with other components of the composition material during the second stage of the mixing process. 38
the method of. 40. The method of claim 38, wherein said first step of said mixing step comprises a milling step. 41. The method of claim 39, wherein said first step of said mixing step comprises a milling step.