Dielectric Porcelain Composition for High-Temperature Stability
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Solution Overview
Problem
Existing dielectric porcelain compositions, such as barium titanate, fail to maintain a stable dielectric constant at high temperatures, and lead-based alternatives are environmentally hazardous, while lead-free bismuth niobate compositions face challenges with sintering temperature and density when increasing the KNN ratio for improved temperature properties.
Innovation Solution
A dielectric porcelain composition expressed by the formula (1−x(0.94Bi1/2Na1/2TiO3−0.06BaTiO3)−xK0.5Na0.5NbO3)+αCuO+βLiF, where x is between 0.14 and 0.28, α and β meet specific conditions, allowing for sintering at temperatures below 1050°C with high sintering density and reduced temperature dependence of the dielectric constant, using silver palladium alloy electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the KNN ratio is increased in lead-free bismuth niobate composition to improve temperature properties, then the temperature dependence of dielectric constant is reduced, but the sintering temperature increases and sintering density drops
Solution Approach 1:
The patent changes the chemical composition parameters by introducing CuO and LiF additives in specific ratios (α and β parameters) to the BNT-BT-KNN system. This composition modification enables sintering at lower temperatures (900-1050°C) while achieving high sintering density (93% or above) and maintaining good temperature properties with low dielectric constant temperature dependence
Solution Approach 2:
The patent creates a composite material system combining BNT-BT-KNN base composition with CuO and LiF additives. This composite approach allows the material to achieve both low sintering temperature and high sintering density, while the specific composition ratios control the dielectric properties and temperature stability
2Ease of manufacture
If Ag—Pd electrode composition is used with high Ag ratio for cost advantage, then manufacturing cost is reduced, but sintering temperature must be reduced below 1050°C to prevent Bi and Ag reaction
Solution Approach 1:
The patent modifies the sintering temperature parameter to be below 1050°C (specifically 900-1050°C) to prevent harmful reactions between Bi in the dielectric layer and Ag in the electrode. This temperature control enables the use of cost-effective high-Ag ratio (7/3, 8/2, 9/1) Ag—Pd electrodes while avoiding electrode degradation
3Ease of manufacture
If barium titanate is used as dielectric porcelain composition, then it is widely available and easy to manufacture, but its Curie temperature is near 130°C and specific dielectric constant drops significantly at 150°C or above
Solution Approach 1:
The patent replaces barium titanate with a composite material system based on BNT-BT-KNN. This composite composition combines the advantages of multiple materials: BNT provides high Curie temperature, BT contributes to dielectric properties, and KNN enhances temperature stability. The resulting material maintains stable dielectric constant at high temperatures while remaining manufacturable
4Stability of the object's composition
If Pb-containing dielectric porcelain composition is used for high-temperature applications, then Curie point is around 490°C and dielectric constant is relatively stable until 300°C, but Pb is an environmentally hazardous substance
Solution Approach 1:
The patent extracts and eliminates the harmful Pb component from the dielectric porcelain composition. By removing Pb and replacing it with environmentally friendly BNT-BT-KNN system, the invention achieves the same high-temperature stability (Curie point above 300°C) and dielectric constant stability without environmental hazards, meeting modern eco-friendly requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves a high sintering density of 93% or above and a small rate of change in specific dielectric constant over a wide temperature range, making it suitable for high-temperature applications without using hazardous heavy metals, such as Pb and Sb.
Implementation Method 1
the ceramic sintering temperature is high at 1050° C. or above... sintering can be done in an atmospheric ambience... sintering at temperatures below 1050° C. is desired
Implementation Method 2
specific dielectric constant with good temperature properties even at high temperatures such as 200 to 350° C.... Curie temperature is near 130° C. and therefore its specific dielectric constant drops significantly in a temperature range of 150° C. or above
Data Source
AI summary
A dielectric porcelain composition with a sintering density of 93% or above, is expressed by the composition formula below: 100[1−x(0.94Bi1/2Na1/2TiO3−0.06BaTiO3)−xK0.5Na0.5NbO3]+αCuO+βLiF (wherein x is between 0.14 and 0.28, and α and β meet either (I) α is between 0.4 and 1.5, and β is between 0 and 2.4, or (II) α is between 0 and 1.5, and β is between 0.2 and 2.4). The dielectric porcelain composition is Pb-free and can be sintered at low temperature, as well as a dielectric element having such composition.