Dielectric Ceramic Composition for Laminated Capacitor Grain Control
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Solution Overview
Problem
Laminated ceramic capacitors with dielectric layers of reduced thickness face degradation in lifetime characteristics under high electric field intensities and high temperature loading tests due to increased variation in grain diameters.
Innovation Solution
A dielectric ceramic composition of (Ba1-xCax)TiO3 with specific mol percentages of Al, V, Mg, Re, Mn, and Si is used, where Re includes metal elements like Y, La, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb, to reduce grain diameter variation and enhance reliability under high electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dielectric layer thickness is reduced to increase capacitance, then the capacitance increases, but the lifetime characteristics are degraded under high electric field intensity
Solution Approach 1:
The patent changes the chemical composition parameters of the dielectric ceramic by adding specific amounts of Al, V, Mg, and Re elements to the (Ba, Ca)TiO3 base material. This compositional parameter change enables the ceramic to maintain grain size uniformity even when fired at high temperatures, which is critical for maintaining reliability in thin-film capacitors with reduced dielectric layer thickness.
Solution Approach 2:
The patent creates a composite dielectric material by combining (Ba, Ca)TiO3 with multiple additive elements (Al, V, Mg, Re). This composite structure leverages the high dielectric constant of barium titanate while the added elements provide grain growth control and structural stability, resolving the contradiction between achieving high capacitance in thin layers and maintaining long-term reliability under electric field stress.
2Quantity of substance
If various elements are added to increase dielectric constant, then the dielectric constant increases, but the variation in grain diameters increases
Solution Approach 1:
The patent carefully controls the concentration parameters of added elements within specific ranges: Al (0.01-0.10 mol%), V (0.01-0.05 mol%), Mg (0.01-0.05 mol%), and Re (0.01-0.10 mol%). These precise parameter controls ensure that the elements enhance dielectric constant without causing excessive grain growth or aggregation, thereby maintaining uniform grain diameter distribution.
Solution Approach 2:
The patent introduces different elements with specific local functions: Al and V for grain boundary control, Mg for lattice substitution and grain growth inhibition, and Re (rare earth) for stabilizing the perovskite structure. Each element acts locally to control specific aspects of grain development, collectively achieving both high dielectric constant and uniform grain size.
3Quantity of substance
If the dielectric layer thickness is reduced, then the capacitance increases, but the electric field intensity increases leading to reliability degradation
Solution Approach 1:
The patent modifies the material parameters of the dielectric ceramic through controlled addition of Al, V, Mg, and Re elements. These compositional changes increase the breakdown strength and electrical stability of the material, enabling it to withstand higher electric field intensities that result from reduced layer thickness, thus maintaining reliability while achieving higher capacitance.
Data Source
AI summary
A laminated ceramic capacitor which exhibits excellent lifetime characteristics in a high temperature loading test uses a dielectric ceramic constituting the dielectric layers which contains (Ba1-xCax)TiO3 as its main constituent, and contains a parts by mol of Al, b parts by mol of V, c parts by mol of Mg, and d parts by mol of Re with respect to 100 parts by mol of the (Ba1-xCax)TiO3. The Re is at least one metal element selected from among Y, La, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, and the x, a, b, c, and d respectively satisfy the conditions of 0.050≦x≦0.150, a≧0.15, 0.05≦b≦0.50, c≦0.50, and d≧1.00.