Lead-Free Barium Titanate MLCC for Low-Temperature Sintering
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Solution Overview
Problem
Current dielectric ceramic compositions struggle to achieve a dielectric constant of over 2000 without using lead or cadmium, while maintaining stability over a wide temperature range and under DC bias voltage, and require high sintering temperatures, making them costly and inefficient for multilayer ceramic chip capacitors.
Innovation Solution
A lead-free and cadmium-free dielectric composition system based on barium titanate with guest ions like zinc, boron, bismuth, and silver, fired at temperatures below 1000°C, which maintains a stable dielectric constant and low dielectric loss even under DC bias, using a blend of oxides such as BaTiO3, ZnO, B2O3, Bi2O3, and Ag2O, allowing for the use of high silver content internal electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lead or cadmium is added to reduce sintering temperature, then sintering temperature decreases to 1050-1150°C, but the composition contains harmful substances that violate environmental regulations
Solution Approach 1:
The patent extracts and removes lead and cadmium from the dielectric composition, replacing them with alternative oxides (Bi2O3, ZnO, B2O3, Nb2O5, TiO2, CuO, NiO, WO3, MnO, SiO2, CeO2) that achieve the same sintering temperature reduction without environmental harm. This extraction of harmful substances while maintaining functional performance directly resolves the contradiction between temperature reduction and environmental compliance.
Solution Approach 2:
The patent creates a composite dielectric material system combining barium titanate with multiple guest oxide additives. This composite approach allows the material to achieve low-temperature sintering (below 1000°C) through synergistic effects of multiple oxides, particularly Bi2O3 and ZnO, while maintaining lead-free and cadmium-free composition that satisfies environmental regulations.
2Object-affected harmful factors
If sintering temperature is reduced below 1000°C without lead or cadmium, then environmental compliance is achieved, but achieving a dielectric constant over 2000 becomes difficult
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating specific ratios of guest oxide additives (Bi2O3: 0.1-5 wt%, ZnO: 0.1-5 wt%, B2O3: 0.1-5 wt%, Nb2O5: 0.1-5 wt%, TiO2: 0.1-5 wt%, CuO: 0.1-5 wt%, NiO: 0.1-5 wt%, WO3: 0.1-5 wt%, MnO: 0.1-5 wt%, SiO2: 0.1-5 wt%, CeO2: 0.1-5 wt%) into the barium titanate matrix. These parameter changes enable the material to achieve both low-temperature processing and high dielectric constant (>2000) simultaneously, resolving the contradiction between environmental compliance and dielectric performance.
Solution Approach 2:
The patent develops a composite dielectric system where barium titanate is combined with multiple guest oxide additives that work synergistically. The composite structure allows low-temperature sintering while achieving high dielectric constant through the combined effects of the base material and additive phases, particularly Bi2O3 and ZnO which promote grain growth and dielectric properties at lower temperatures.
3Quantity of substance
If conventional dielectric compositions are used to achieve high dielectric constant, then dielectric constant increases, but sintering temperature must be above 1250°C which increases production cost
Solution Approach 1:
The patent changes the compositional parameters by introducing multiple guest oxide additives that act as sintering aids and grain growth promoters. These additives enable the dielectric constant to exceed 2000 at sintering temperatures below 1000°C, significantly reducing the thermal energy input required compared to conventional compositions that require temperatures above 1250°C, thereby reducing production costs.
Solution Approach 2:
The patent employs small amounts of inexpensive oxide additives (totaling only 0.1-10 wt% of the composition) that serve as temporary sintering aids during processing. These additives facilitate low-temperature sintering and can be consumed or transformed during the firing process, enabling cost-effective production by replacing the need for expensive high-temperature processing infrastructure.
4Object-affected harmful factors
If lead-free and cadmium-free compositions are developed, then environmental compliance is achieved, but stability of dielectric constant over wide temperature range and under DC bias becomes challenging
Solution Approach 1:
The patent creates a composite dielectric system where the interaction between barium titanate and multiple guest oxide additives (particularly Bi2O3, ZnO, and Nb2O5) produces synergistic effects that stabilize the dielectric constant. The composite structure provides compositional stability over wide temperature ranges (-55°C to +125°C) and under DC bias conditions while maintaining environmental compliance, resolving the contradiction between green chemistry and performance stability.
Solution Approach 2:
The patent optimizes the compositional parameters by controlling the ratios of multiple oxide components within specific ranges. This parameter optimization ensures that the dielectric constant remains stable (X7R: ±15% over -55°C to +125°C; BX: ±25% under DC bias) while maintaining a lead-free and cadmium-free composition, achieving both environmental compliance and electrical stability.
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 solution provides multilayer ceramic capacitors with a high dielectric constant, low dielectric loss, and stability across a wide temperature range and under DC bias, meeting X7R and BX standards, while reducing production costs by using less expensive silver-rich electrodes.
Implementation Method 1
fired at temperatures below 1000°C
Implementation Method 2
dielectric constant does not alter from its base value by more than 15 percent over a wide temperature range
Data Source
AI summary
Multilayer ceramic chip capacitors which satisfy X7R and BX requirements and which are compatible with silver-palladium internal electrodes are made in accordance with the invention. The capacitors exhibit desirable dielectric properties (high capacitance, low dissipation factor, high insulation resistance), excellent performance on highly accelerated life testing, and very good resistance to dielectric breakdown. The dielectric layers comprise a lead-free and cadmium-free barium titanate base material doped with other metal oxides such oxides of zinc, boron, bismuth, cerium, tungsten, copper, manganese, neodymium, niobium, silver, barium, silicon and nickel in various combinations. The dielectric ceramic materials herein can be sintered together (fired) at less than 1000° C. with an inner electrode having more than 80 wt % Ag and less than 20 wt % Pd to form a multilayer ceramic capacitor (MLCC).