Vitrified ceramic body composition sintered at low temperatures and vitrified ceramic product produced with said composition

Abstract

The invention relates to a vitrified ceramic body composition, which enables the raw materials in the vitrified ceramics to be sintered at temperatures lower than 1100°C, enables the sintering temperature to be reduced to as low as 900°C, and enables a finished product with high mechanical strength to be obtained owing to the simultaneously formed mullite and anorthite crystals, and to a vitrified ceramic product produced with said composition. The vitrified ceramic body composition according to the invention includes, in addition to clay and kaolin, a melting agent for enabling to reduce the sintering temperature to as low as 900°C and a crystal nucleating agent for assisting the crystal formation.

Description

[0001] DESCRIPTION

[0002] VITRIFIED CERAMIC BODY COMPOSITION SINTERED AT LOW TEMPERATURES AND VITRIFIED CERAMIC PRODUCT PRODUCED WITH SAID COMPOSITION

[0003] Subject of the Invention

[0004] The invention relates to a vitrified ceramic body composition, which enables the raw materials in the vitrified ceramics to be sintered at temperatures lower than 1100°C, enables the sintering temperature to be reduced to as low as 900°C, and enables a finished product with high mechanical strength to be obtained owing to the simultaneously formed mullite and anorthite crystals, and to a vitrified ceramic product produced with said composition.

[0005] State of the Art

[0006] Sintering is the process of heating the ceramic raw materials in powder form at a certain temperature, homogenizing said ceramic raw materials, and enabling said ceramic raw materials to intensify in the meantime to form a strong and compact structure. The sintering process involved in the production of the vitrified ceramic products is of great importance for obtaining a finished product with desired physical and mechanical properties as well as ensuring the efficiency and the sustainability of the production. The consumption of energy in the ceramic sanitary ware industry mainly stems from the use of the thermal energy in the body sintering process.

[0007] The vitrified body in the ceramic sanitary ware is defined as a ceramic material, which generally has a low water absorption property with a water absorption rate below 0.5% and which has attained a dense structure. This type of bodies are sintered at elevated temperatures to render the same nonporous and water-resistant. The vitrified ceramics are usually sintered for a duration of 16-22 hours at the sintering temperatures varying in the range of 1200-1300°C. According to the state of the art, it is necessary to maintain a peak temperature in the range of 1200-1300°C during the sintering stage so that the properties of the vitrified ceramic recipes like mechanical strength, porosity, and water absorption rate may satisfy the ideal conditions.Some components constituting the microstructure of the ceramic material are formed during the sintering. For example, the crystals in the vitrified ceramic bodies, e.g., the mullite crystals, are the important components that constitute the microstructure of the ceramic material and they usually emerge during the sintering. These crystals play a key role in the improvement of the mechanical strength, thermal resistance, and chemical stability.

[0008] The crystals are formed during the sintering through the processes of nucleation and crystal growth. At sufficiently high temperatures, the atoms or the ions are rearranged inside an amorphous phase to form the small crystal structures, i.e., the nuclei; after which, the crystal growth occurs upon the addition of the atoms or the ions on the nuclei in a regular manner. In order for the mentioned nuclei to be able to grow and become crystals, the viscosity value must remain within a certain range during the sintering. In the vitrified bodies according to the state of the art, it is necessary to perform the sintering process at an elevated temperature for a long duration, in order to provide the viscosity value suitable for forming the nuclei and maintain this viscosity level throughout the crystal growth. However, such elevated sintering temperatures and such length of the sintering process reduce the efficiency in the production process, lead to the loss of time, and increase the energy consumption and the costs.

[0009] Some of the studies currently being conducted in a manner different from the conventional production methods with a view to provide energy savings and reduce the productions costs in the production of the vitrified products include the use of the nanopowders, the use of the sintering additives, and the use of the binders with low melting point. In addition to these, the methods of microwave sintering, reactive sintering, spark plasma sintering (SPS), and high pressure sintering are among the methods being studied for the purpose of achieving energy savings. However, said materials and methods lead to some drawbacks in the production process or in the finished product, and for this reason, they are unable to be applied in practice and are unable to be used in the large-scale productions requiring sustainability. Further, since said materials and methods may not be easily integrated into the conventional kiln type and the conventional production method, they cause the optimization problems and the cost disadvantages in the process.For the conventional vitrified body formulations, the primary raw materials such as clay, kaolin, feldspar, and quartz are used. For these products, the feldspars with melting temperatures above 1150°C are usually used a sintering aid or melting agent. In order to reach the viscosity value required for achieving the intensification at which the desired mechanical properties are formed in the finished product and in order to maintain said value, it is required to fire the feldsparcontaining body formulation for 16-22 hours at a temperature of 1200°C and above. However, such long durations and elevated temperatures employed in the state of the art lead to high energy consumption. Besides, the long firing durations increase the overall production time and result in inefficiency.

[0010] For the reasons stated above, there is a need for developing the vitrified body compositions, which enable to lower the sintering temperatures and shorten the sintering duration for the raw materials in the vitrified ceramics, while at the same time enabling to preserve the physical and mechanical properties of the ceramics, reducing loss of time, energy consumption and costs, and increasing production efficiency in the production process for the ceramic sanitary ware, said vitrified body compositions allowing the ceramic production to be carried out upon an optimization of the conventional production method without having to alter the conventional kiln type.

[0011] Object of the Invention

[0012] An object of the invention is to develop a vitrified body composition, which enables the raw materials in the vitrified ceramics to be sintered at 900-950°C, that is, at a temperature below 1100°C, the lowest sintering temperature of the prior art. According to the invention, instead of feldspar melting at about 1150°C, a melting agent, which melts at lower temperatures and enables the desired viscosity to be reached, is used. Moreover, in the composition according to the invention, the nucleating agents are present to assist the growth of the nuclei into the crystals, said nucleating agents already containing such crystals. In this way, the nuclei and thus the crystalline structure grow rapidly and the finished vitrified ceramic product is obtained at a lower temperature and in a shorter time compared to the prior art.Owing to the presence of the melting agent and the crystal nucleating agent in the body composition according to the invention and owing to the ratios of said agents determined along with all the other ingredients, it is made possible to lower the sintering temperatures and shorten the sintering duration. According to the invention, due to the shortening of the sintering duration and the lowering of the peak temperature, an efficiency increase is achieved in the process of ceramic sanitary ware production. This in turn contributes to the reduction of the loss of time and the consumption of energy, and thus, to sustainability.

[0013] Another object of the invention is to develop a vitrified ceramic product, the mechanical endurance and strength of which meet the currently applicable standards, despite being sintered at low temperatures. With the help of the nucleating agents present among the ingredients of the body composition according to the invention, it is possible to obtain the mullite crystals at lower temperatures compared to the prior art, and, in addition to the mullite, the formation of the anorthite crystals is enabled in the body. Withing the scope of the invention, owing to the three-dimensional lattice formed with the anorthite crystals in addition to the mullite crystals, it is possible to produce a vitrified ceramic product having high strength property even at a sintering temperature in the range of 900-950°C, i.e., at a sintering temperature lower than those used in the prior art. Owing to the ingredients and the ratios of the same in the body according to the invention, it is possible to achieve a strength similar to the strength of a body formed according to the prior art at an elevated temperature only with the mullite crystals.

[0014] Owing to the use of the crystal nucleating agent according to the invention, the nucleation temperature is reduced to temperatures lower than those of the prior art and the crystals that confer the strength are enabled to form and grow at a lower temperature. The crystalline structures obtained in the prior art with the vitreous phase formed and with the viscosity value reached only at temperatures in the range of 1200-1300°C may be obtained at temperatures in the range of 900-950°C owing to the body composition according to the invention.

[0015] Another object of the invention is to develop a vitrified body composition, which may be easily used by way of integration into the conventional production method, without the need to alter the conventional kiln type. Owing to the ingredients of the composition according to the invention and the determined ratios for said ingredients, it is possible to obtain a vitrified ceramic product,which is sintered at a lower temperature, the overall firing duration of which is shortened, and the mechanical strength of which is increased compared to the prior art, simply by changing the kiln regime and without having to employ different kiln technologies.

[0016] Description of the Figures

[0017] Figure 1: TG-DTA analysis graph for the vitrified body according to the invention

[0018] Figure 2: TG-DTA analysis graph for the body according to the prior art

[0019] Figure 3: Optical dilatometer analysis graph for the vitrified body according to the invention Figure 4: Optical dilatometer analysis graph for the body according to the prior art

[0020] Figure 5: XRD analyses for the body according to the prior art

[0021] Figure 6: Comparative XRD analyses for the body according to the prior art and the body according to the invention

[0022] Figure 7: SEM images of the bodies (A. SEM image of the body according to the invention, B. SEM image of the body according to prior art)

[0023] Detailed Description of the Invention

[0024] The invention relates to a vitrified ceramic body composition, which enables the raw materials in the vitrified ceramics to be sintered at temperatures lower than 1100°C, enables the sintering temperature to be reduced to as low as 900°C, and enables a finished product with high mechanical strength to be obtained owing to the simultaneously formed mullite and anorthite crystals, and to a vitrified ceramic product produced with said composition.

[0025] The vitrified ceramic body composition according to the invention comprises, in addition to clay and kaolin, a melting agent for enabling to reduce the sintering temperature to as low as 900°C and a crystal nucleating agent for assisting the crystal formation.

[0026] In an embodiment of the invention, the vitrified body composition comprises 30-35% by volume clay, 25-30% by volume a melting agent, 20-25% by volume kaolin, and 15-20% by volume a crystalnucleating agent. In the preferred embodiment of the invention, the vitrified body composition comprises 31-32% by volume clay, 24-25% by volume kaolin, 27-28% by volume a melting agent, and 16-17% by volume a crystal nucleating agent. The ingredient ratios (by volume) in the body composition according to a preferred embodiment of the invention are given in Table 1 below.

[0027] Raw Material Ingredient Ratios (by Volume) of the Body

[0028] Composition According to the Invention

[0029] Clay 31.4%

[0030] Kaolin 24.2%

[0031] Melting agent 27.6%

[0032] Crystal nucleating agent 16.8%

[0033]

[0034] Table 1. The ingredient ratios (by volume) of the body composition according to the invention According to the invention, said melting agent is characterized by being a melting agent with an amorphous structure, which has a sintering temperature in the range of 730-770°C, preferably 750°C, and a softening temperature in the range of 850-890°C, preferably 870°C (as determined according to the results obtained by a thermal microscope). The melting agent used in the body was obtained by way of vitrification as a result of melting at certain temperatures followed by rapid cooling. The use of a melting agent in vitreous phase reduces the viscosity of the system, thereby facilitating the transport and the sintering of the materials, which do not melt at lower temperatures (<1100°C), through said system.

[0035] The melting agent in the body composition according to the invention comprises the components of 57-62% by weight silicon dioxide (silica) (SiCh), 15-17% by weight boron trioxide (B2O3), 6-9% by weight aluminum oxide (alumina) (AI2O3), 8-11% by weight calcium oxide (CaO), 2-6% by weight potassium oxide (K2O), and 2-6% by weight sodium oxide (Na2O), as determined by the X-Ray Fluorescence (XRF) analysis.

[0036] For the selection of the melting agent, the thermal behavior of the body was examined especially via thermal microscope and model studies and it was attempted to bring the system viscosity at 900-950°C into the same range as the system viscosity of the bodies according to the state of theart at 1200°C. The wetting capabilities of the melting agents included in the system and the penetration and diffusion effects of these agents with the other components in the system were examined via the model studies. According to these studies, the melting agent selected within the scope of the invention was observed to carry the body with a certain viscosity and contribute to the sintering by filling the intergranular pores.

[0037] The melting agent determined for use within the scope of the invention was selected as a melting agent that would be capable of enabling the formation of the liquid phase in the system, wetting the other body components, and bringing the viscosity to the desired value at the desired low temperature (T~900°C). Moreover, the amount of the melting agent in the composition was determined as 25-30% by volume, preferably 27-28% by volume, such that it is possible to obtain a liquid phase sufficient for satisfying the viscous sintering requirements. In the studies conducted within the scope of the invention, the volume ratios of the body components were theoretically calculated, instead of the mass ratios of the same, in order to examine the formation of the liquid phase. Accordingly, when the content of the melting agent rises above 30% by volume, it was observed that the viscosity for the body system decreases and the sintering increases, whereas the strength decreases despite an increased firing shrinkage. On the other hand, when the content of the melting agent drops below 30% by volume, it was observed that the open pores remain within the body, which in turn increases % water absorption, as a result of a reduction in the amount of the liquid phase and an increase in the system viscosity, even though the firing shrinkage meets the required standard.

[0038] The crystal nucleating agent, another critical component in the vitrified body composition, is a ceramic powder, which comprises the below-mentioned components at the specified ratios, has the mineralogical properties specified in the XRD analysis (Figure 6), and has a particle size range indicated in Table 2.

[0039] The crystal nucleating agent in the body composition according to the invention comprises the components of 68-73% by weight silicon dioxide (silica) (SiCh), 21-24% by weight aluminum oxide (alumina) (AI2O3), and 2-6% by weight sodium oxide (Na2O), as determined by XRF analysis. In the preferred embodiment of the invention, the crystal nucleating agent comprises, in addition to theother components, 0-3% by weight calcium oxide (CaO), 0-3% by weight potassium oxide (K2O), 0-1% by weight zirconium dioxide (zirconia) (ZrO2), and 0-1% by weight magnesium oxide (MgO). According to the invention, an ingredient amount given as 0-3% by weight means 0% < ingredient amount < 3%, i.e., indicates that the amount of the ingredient in question is 3% or less than 3% and more than 0%. Similarly, an ingredient amount given as 0-1% by weight means 0% < ingredient amount < 1%, i.e., indicates that the amount of the ingredient in question is 1% or less than 1% and more than 0%.

[0040] 35-50% of said crystal nucleating agent has a particle size greater than 32 pm, 10-25% of said crystal nucleating agent has a particle size greater than 63 pm, 5-12% of said crystal nucleating agent has a particle size greater than 90 pm, 1.5-4% of said crystal nucleating agent has a particle size greater than 125 pm, and 1.5-3% of said crystal nucleating agent has a particle size greater than 140 pm. In an embodiment of the invention, in addition to the stated particle sizes, 0-2% of the crystal nucleating agent has a particle size greater than 180 pm and 0-0.3% of the crystal nucleating agent has a particle size greater than 300 pm.

[0041] According to the invention, an ingredient amount given as 0-2% by weight means 0% < ingredient amount < 2%, i.e., indicates that the amount of the ingredient in question is 2% or less than 2% and more than 0%. Similarly, an ingredient amount given as 0-0.3% by weight means 0% < ingredient amount < 0.3%, i.e., indicates that the amount of the ingredient in question is 0.3% or less than 0.3% and more than 0%.

[0042] Particle Size % Amount

[0043] >300 pm 0-0.3

[0044] >180 pm 0-2

[0045] >140 pm 1.5-3

[0046] >125 pm 1.5-4

[0047] >90 pm 5-12

[0048] >63 pm 10-25

[0049]

[0050] >32 pm 35-50

[0051]

[0052] Table 2. XRD analysis showing the percentage distribution of the material fractions with different particle sizes, present in the crystal nucleating agent in the body composition according to the invention

[0053] Within the scope of the invention, as can be seen in Figure 6, the crystalline phases forming inside the structure were detected via XRD phase analysis. It was possible to form in the intended manner the quartz and the mullite phases, which are observed in the body according to the prior art, also in the body according to the invention. In addition, the formation of anorthite was also noted in the body, along with the CaO compound present in the melting agent (Figure 6).

[0054] The body according to the prior art and the body according to the invention were compared via XRF chemical analysis. According to the results of XRF chemical analysis, an increase was observed in the components CaO and B2O3 in the composition according to the invention, owing to the use of a melting agent and a crystal nucleating agent instead of the feldspar-containing composition used in the prior art. This observed increase is supported by an increase in the anorthite and the mullite crystals, as seen in XRD analysis (Figure 6).

[0055] The crystal nucleating agent that supports the crystal formation in the composition enables the mechanical strength of the finished vitrified product to be increased by the desired extent at low temperatures. Owing to the synergistic action of the mullite-anorthite crystals, the strength of the ceramics is enhanced. When the mechanical strengths of the products obtained with the body according to the invention are measured, it can be seen that the mechanical strengths, which are similar to those of the ceramics fired at a temperature above 1200°C, are possible to obtain even in the temperature range of 900-950°C.

[0056] Within the scope of the invention, a thermomechanical analysis (TMA) was performed for the measurement of the melting viscosity of the system at the specified temperatures, and accordingly, the changes in the composition, which are required to reach, at temperatures around 900°C, the viscosity value necessary for sintering the body according to the prior art, were determined (Table 3).Analysis of the Analysis of the body Analysis of the body body according to according to the according to the

[0057] the prior art at invention at 900°C invention at 925°C

[0058] 1200°C

[0059] Slope 0.000459458 0.000631 0.000640885

[0060] Viscosity

[0061] 2.18 x lOA9 1.5836 x 10A9 1.5603 x 10A9

[0062] (h (Poise))

[0063] Log o io934IO92010919

[0064]

[0065] Table 3. Vitreous phase viscosities of the body according to the prior art at a temperature employed in the prior art (1200°C) and of the body according to the invention at a low target temperature (950°C)

[0066] In the TMA analysis, a curve of size change rate was plotted based on a % shrinkage curve for the raw body section samples, depending on the temperature and the load. The viscosity value of a sample at the desired temperature was calculated by taking the reciprocal of the slope of a curve obtained from the graphs for the dimensional change rate and the uniaxial stress change of the sample (1 / slope). In this analysis, the viscosity value, which the body composition according to the invention is required to reach at the target temperature, preferably a temperature in the range of 900-950°C, was calculated based on the viscosity ( 109'34) of the body according to the prior art at 1200°C. The viscosity of the body composition developed according to the invention was calculated as IO9'20.

[0067] It can be seen from the results of the TMA analysis performed for the body composition according to the invention that the desired viscosity value is reached in the temperature range of 900-950°C (Table 3). The products prepared based on this result was fired by keeping the same at an approximate peak temperature in the range of 900-950°C. Upon an examination of the finished products, the desired mullite, anorthite, quartz, and amorphous phases were detected as a result of the mineralogical analysis.

[0068] Whereas the mullite, quartz, and amorphous phases are obtained in the finished structure when the vitrified bodies of the state of the art are fired at a temperature above 1200°C, the mullite,anorthite, quartz, and amorphous phases were obtained with the composition according to the invention in the temperature range of 900-950°C. With the body according to the invention, the formation of anorthite was observed for the first time ever in the vitrified bodies, and further, it was possible to achieve for the first time the formation of mullite at a temperature below 1100°C. The formation of the mullite at a low temperature was assisted by the nucleating agent and the melting agent with low melting temperature, which were added to the system.

[0069] Scanning Electron Microscope (SEM) images of the body according to the prior art and the body according to the invention are given in Figure 7. In the microstructure of the recipe according to the prior art, the primary (coaxial-circular) and the secondary (needle-like) mullite crystals are observed after the sintering at 1200°C. In the SEM analysis conducted on the body recipe according to the invention, the formation of the primary and secondary mullites was achieved in the structure during the sintering at 950°C and the anorthite crystals identified in the XRD analysis were also detected. It was determined that in terms of internal structure, the secondary mullite crystals with a needle-like structure, which provide the main strength increase in the body according to the invention, were detected in these SEM images in a manner similar to the prior art (Figure 7A). Owing to the invention, it was possible for the first time in the literature to form both the primary and the secondary mullites at 950°C.

[0070] The melting agent in the composition according to the invention is able to reach the required viscosity value at temperatures much lower compared to those of the prior art, and owing to the crystal nucleating agent added to the system, the existing nuclei are able to easily grow inside the vitreous phase formed by the melting agent, without the need for extra time and temperature for the formation of the nuclei. In this way, it is possible to form the crystals that will increase the mechanical strength, without adding to the system the quartz with a melting temperature of 1785°C and without raising the sintering temperature of the system. The properties of strength, firing shrinkage, and water absorption possible to obtain at a temperature of 1200°C according to the prior art are able to be obtained at 950°C with the body according to the invention (Table 4).% Water Temper % Firing Absorption Sample Strength

[0071] ature Shrinkage (Unglazed Region) Body according to the

[0072] 1200 400 8.36 1.26 prior art

[0073] Body according to the

[0074] 950 370-425 8.16 1.30

[0075] invention

[0076]

[0077] Table 4. Comparison of the properties of temperature, strength, firing shrinkage, and water absorption in the body according to the prior art and the body according to the invention It can be seen as a result of the studies performed that the body according to the invention, while being able to be sintered at a lower temperature such as 950°C, exhibits a similar performance to the prior art with regard to strength and other properties. This offers great advantage in terms of energy savings and the reduction of the productions costs; further, the dimensional stability and the product quality are improved due to the decrease in the firing shrinkage.

[0078] As described above, many tests and characterization studies were conducted for the development of the vitrified body composition according to the invention. Thermogravimetric analysis -differential thermal analysis (TG-DTA) was performed for the body according to the prior art and the body according to the invention and the thermal behavior of the bodies exhibited depending on the temperature and the mass losses from the same during the firing were examined. As expected, the mass losses from the body according to the prior art and the body according to the invention were observed to be similar. On the other hand, whereas the temperature at which the phase transformation occurred, i.e., the strength-increasing crystals (like mullite) formed, was ~1000°C in the body according to the prior art, the temperature at which the crystals formed was reduced to the values on the order of 900-950°C with the body according to the invention (Figure 1, Figure 2).Moreover, within the scope of the invention, the sintering temperatures and the sintering rates of the prepared recipes were analyzed by means of an optical dilatometer, in order to determine whether there was a temperature drop. The sample of the body according to the prior art started to be sintered at 1126°C and reached the maximum sintering rate at 1199°C. On the other hand, the sample of the body according to the invention started to be sintered at 859°C and reached the maximum sintering rate at 950°C (Figure 3, Figure 4). Further, Harkort's tests (temperaturedependent cracking resistance tests) were completed on the finished vitrified ceramic product and no crack was encountered.

[0079] Said vitrified ceramic product is a product obtained by sintering at 1100-900°C, preferably at 900-950°C, a ceramic composition, which comprises 30-35% by volume clay, 25-30% by volume a melting agent, 20-25% by volume kaolin, and 15-20% by volume a crystal nucleating agent. In the preferred embodiment of the invention, said vitrified ceramic product is a ceramic sanitary ware, preferable a toilet.

[0080] As a result of all the analyses performed, it was demonstrated that it is possible to obtain a vitrified body composition, which enables to lower the sintering temperatures and shorten the sintering duration for the raw materials in the vitrified ceramics, while at the same time enabling to preserve the physical and mechanical properties of the ceramics, reducing loss of time, energy consumption and costs, and increasing production efficiency in the production process for the ceramic sanitary ware, said vitrified body composition allowing the ceramic production to be carried out upon an optimization of the conventional production method without having to alter the conventional kiln type, as well as to obtain a vitrified ceramic product using said composition.

Claims

CLAIMS1. A vitrified body composition characterized in that said vitrified body composition comprises 30-35% by volume clay, 25-30% by volume a melting agent, 20-25% by volume kaolin, and 15-20% by volume a crystal nucleating agent.

2. A vitrified body composition according to Claim 1 characterized in that said vitrified body composition comprises 31-32% by volume clay, 24-25% by volume kaolin, 27-28% by volume a melting agent, and 16-17% by volume a crystal nucleating agent.

3. A vitrified body composition according to Claim 1 or 2 characterized in that said vitrified body composition comprises 31.4% by volume clay, 24.2% by volume kaolin, 27.6% by volume a melting agent, and 16.8% by volume a crystal nucleating agent.

4. A vitrified body composition according to any one of the preceding claims characterized in that said melting agent comprises 57-62% by weight SiC>2, 15-17% by weight B2O3, 6-9% by weight AI2O3, 8-11% by weight CaO, 2-6% by weight K2O, and 2-6% by weight Na2O.

5. A vitrified body composition according to any one of the preceding claims characterized in that said melting agent is a melting agent with an amorphous structure, which has a sintering temperature in the range of 730-770°C and a softening temperature in the range of 850-890°C.

6. A vitrified body composition according to Claim 5 characterized in that said melting agent is a melting agent with an amorphous structure, which has a sintering temperature of 750°C and a softening temperature of 870°C.

7. A vitrified body composition according to any one of Claims 1-3 characterized in that said crystal nucleating agent comprises 68-73% by weight SiC>2, 21-24% by weight AI2O3, and 2- 6% by weight Na2O.

8. A vitrified body composition according to Claim 7 characterized in that said crystal nucleating agent further comprises 0-3% by weight CaO, 0-3% by weight K2O, 0-1% by weight ZrO2, and 0-1% by weight MgO.

9. A vitrified body composition according to any one of Claims 1-3, 7 or 8 characterized in that 35-50% of said crystal nucleating agent has a particle size greater than 32 pm, 10-25% of said crystal nucleating agent has a particle size greater than 63 pm, 5-12% of said crystal nucleating agent has a particle size greater than 90 pm, 1.5-4% of said crystal nucleating agent has a particle size greater than 125 pm, and 1.5-3% of said crystal nucleating agent has a particle size greater than 140 pm.

10. A vitrified body composition according to Claim 9 characterized in that 0-2% of said crystal nucleating agent has a particle size greater than 180 pm and 0-0.3% of said crystal nucleating agent has a particle size greater than 300 pm.

11. A vitrified ceramic product comprising a vitrified body composition according to any one of the preceding claims.

12. A vitrified ceramic product according to Claim 11 characterized in that said vitrified ceramic product comprises the mullite and anorthite crystals.

13. A vitrified ceramic product according to Claim 11 or 12 characterized in that said vitrified ceramic product is a ceramic sanitary ware.

14. A vitrified ceramic product characterized in that said vitrified ceramic product comprises a ceramic body comprising 30-35% by volume clay, 25-30% by volume a melting agent, 20- 25% by volume kaolin, and 15-20% by volume a crystal nucleating agent.

15. A vitrified ceramic product according to Claim 14 characterized in that said vitrified ceramic product comprises a ceramic body comprising 31-32% by volume clay, 24-25% by volume kaolin, 27-28% by volume a melting agent, and 16-17% by volume a crystal nucleating agent.

16. A vitrified ceramic product according to Claim 14 or 15 characterized in that said vitrified ceramic product comprises a ceramic body comprising 31.4% by volume clay, 24.2% by volume kaolin, 27.6% by volume a melting agent, and 16.8% by volume a crystal nucleating agent.

17. A vitrified ceramic product according to any one of Claims 14-16 characterized in that said melting agent comprises 57-62% by weight SiC>2, 15-17% by weight B2O3, 6-9% by weight AI2O3, 8-11% by weight CaO, 2-6% by weight K2O, and 2-6% by weight Na2O.

18. A vitrified ceramic product according to any one of Claims 14-17 characterized in that said melting agent is a melting agent with an amorphous structure, which has a sintering temperature in the range of 730-770°C and a softening temperature in the range of 850- 890°C.

19. A vitrified ceramic product according to Claim 18 characterized in that said melting agent is a melting agent with an amorphous structure, which has a sintering temperature of 750°C and a softening temperature of 870°C.

20. A vitrified ceramic product according to any one of Claims 14-16 characterized in that said crystal nucleating agent comprises 68-73% by weight SiC>2, 21-24% by weight AI2O3, and 2- 6% by weight Na2O.

21. A vitrified ceramic product according to Claim 20 characterized in that said crystal nucleating agent further comprises 0-3% by weight CaO, 0-3% by weight K2O, 0-1% by weight ZrO2, and 0-1% by weight MgO.

22. A vitrified ceramic product according to any one of Claims 14-16, 20 or 21 characterized in that 35-50% of said crystal nucleating agent has a particle size greater than 32 pm, 10- 25% of said crystal nucleating agent has a particle size greater than 63 pm, 5-12% of said crystal nucleating agent has a particle size greater than 90 pm, 1.5-4% of said crystal nucleating agent has a particle size greater than 125 pm, and 1.5-3% of said crystal nucleating agent has a particle size greater than 140 pm.

23. A vitrified ceramic product according to Claim 22 characterized in that 0-2% of said crystal nucleating agent has a particle size greater than 180 pm and 0-0.3% of said crystal nucleating agent has a particle size greater than 300 pm.

24. A vitrified ceramic product according to any one of Claims 14-23 characterized in that said vitrified ceramic product is a vitrified ceramic product obtained by sintering said ceramic body at 900-950°C.

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