Microwave Dielectric Ceramic Composition for Stable τf and High Q×f
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Solution Overview
Problem
Current microwave dielectric ceramic materials face challenges in achieving high Q×f values and small frequency temperature coefficients across a broad temperature range, while also experiencing issues with sintering processes and mechanical strength due to phase impurities and abnormal grain growth.
Innovation Solution
A frequency-stable low-dielectric microwave dielectric ceramic material is prepared using a composition of 70-90% main-phase ceramic material A (MgxMeySiO2+x+y) and 10-30% auxiliary-phase ceramic material B (αRO-bRe2O3-cTiO2) with specific oxide sintering aids, optimized through precise chemical formulations and sintering conditions to enhance stability and reduce sintering temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If CaTiO3 or SrTiO3 is doped to adjust frequency temperature coefficient to nearly 0, then frequency stability is improved, but Q×f value decreases dramatically to about 20000 GHz
Solution Approach 1:
The patent uses a composite ceramic system combining Mg2SiO4 (providing low dielectric constant and high Q×f) with CaTiO3 and SrTiO3 (providing frequency temperature coefficient compensation). This composite approach allows simultaneous achievement of high Q×f (≥60000 GHz) and near-zero frequency temperature coefficient (−5 to +5 ppm/°C), resolving the contradiction between energy loss and frequency stability.
Solution Approach 2:
The patent systematically varies the molar ratios of CaTiO3 and SrTiO3 dopants (with total content of 0.05-0.20 mol) to optimize both Q×f and frequency temperature coefficient. By changing compositional parameters and sintering temperature parameters, the patent achieves the dual goal of high Q×f and near-zero τf without compromising either property.
2Loss of energy
If Mg2SiO4 is used as base material, then Q×f value is high (270000 GHz), but coefficient of thermal expansion is high (∼10 ppm/°C) reducing device reliability
Solution Approach 1:
The patent combines Mg2SiO4 with CaTiO3 and SrTiO3 to create a composite ceramic that maintains the high Q×f (≥60000 GHz) of Mg2SiO4 while the presence of perovskite phases modifies the thermal expansion behavior. This composite approach preserves the low dielectric loss特性 of Mg2SiO4 while improving thermal stability and reducing thermal expansion-related reliability issues.
3Ease of manufacture
If sintering process is used to prepare Mg2SiO4 ceramics, then ceramic material is formed, but second phase MgSiO3 or incompletely reacted SiO2 forms due to diffusion rate difference, deteriorating dielectric properties
Solution Approach 1:
The patent uses CaTiO3 and SrTiO3 as intermediary phases that facilitate more uniform diffusion and reaction during sintering. These perovskite phases act as mediators that help prevent the formation of harmful second phases like MgSiO3 and incompletely reacted SiO2, thereby maintaining high dielectric properties (Q×f ≥ 60000 GHz) while enabling successful ceramic formation through sintering.
Solution Approach 2:
The patent optimizes sintering parameters including temperature (1200-1400°C), time (2-4 hours), and atmospheric conditions to control the diffusion rates and prevent second phase formation. By carefully controlling these parameters, the patent achieves complete reaction of SiO2 while maintaining the desired phase composition and high dielectric properties.
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 approach results in improved frequency stability, higher Q×f values, and a broad sintering temperature range, addressing the limitations of existing materials by optimizing the frequency temperature coefficient and suppressing abnormal grain growth, thus enabling reliable use in devices like dielectric filters and duplexers for mobile communications.
Implementation Method 1
The auxiliary-phase ceramic material B is composed of αRO-bRe2O3-cTiO2, R is at least one of Ca or Sr, and Re2O3 is at least two of Sm2O3, Nd2O3, Y2O3, Al2O3 and La2O3
Implementation Method 2
τf of Mg2SiO4 is adjusted to −3.62 ppm/° C., while obtaining higher Q×f value
Implementation Method 3
a preparation method of a frequency-stable low-dielectric microwave dielectric ceramic material
Implementation Method 4
0 to 1.0% of an oxide sintering aid C, and the sum of mass percentage of the main-phase ceramic material A, the auxiliary-phase ceramic material B and the oxide sintering aid C is 100%
Data Source
AI summary
The present invention relates to a frequency-stable low-dielectric microwave dielectric ceramic material and a preparation method thereof. The material is prepared from the following components in percentage by mass: 70-90% of a main-phase ceramic material A, 10-30% of an auxiliary-phase ceramic material B and 0-1.0% of an oxide sintering aid C. The main-phase ceramic material A is MgxMeySiO2+x+y; the auxiliary-phase ceramic material B is composed of αRO-bRe2O3-cTiO2, R is at least one of Ca or Sr, Re2O3 is at least two of Sm2O3, Nd2O3, Y2O3, Al2O3 and La2O3; and the oxide sintering aid C is at least one of MnO2, WO3 and CeO2.