硅酸盐学报2025，Vol.53Issue(10)：2841-2853,13.DOI:10.14062/j.issn.0454-5648.20250303
La2O3-B2O3-CaO-P2O5玻璃/Al2O3复合低温共烧陶瓷材料介电性能优化
Optimization of Dielectric Properties for La2O3-B2O3-CaO-P2O5 Glass/Al2O3 Low-Temperature Co-Fired Ceramic Composite
摘要
Abstract
Introduction Low-temperature co-fired ceramic(LTCC)serves as a critical material for high-performance electronic packaging.Reducing the dielectric loss of LTCC materials can minimize signal attenuation in high-frequency transmission and enhance circuit integration.Based on material composition,LTCC materials can be classified into three categories,i.e.,glass-ceramic systems,ceramic systems,and glass/ceramic composite systems.Glass-ceramic systems typically exhibit a low dielectric loss but suffer from inferior mechanical properties and corrosion resistance.Ceramic systems are often employed in medium-and high-dielectric applications,such as dielectric resonators.Reducing the sintering temperature is a key challenge for this system.Glass/ceramic composite systems offer a balanced performance.Their properties can be tailored via adjusting the ratio of the two phases.The La2O3-B2O3 glass/Al2O3 ceramic system serves as one of the representative systems.The sintering and crystallization behavior can be controlled via modifying the glass composition.The La2O3-B2O3-CaO-P2O5(LBCP)glass/Al2O3 composite system demonstrates a significant application potential due to its ability to crystallize low-loss phases such as LaBO3,LaPO4,and CaAl2(BO3)2O during sintering.However,the dielectric loss(tan δ＞1×10-3)of the existing LBCP/Al2O3 composites requires a further improvement.In this paper,alkali metal oxides(i.e.,Na2O and Li2O)were introduced to control the glass crystallization behavior,and the sintering process was refined to enhance the formation of beneficial crystalline phases(i.e.,CaAl2(BO3)2O)to develop low-loss LTCC substrates. Methods La2O3-B2O3-CaO-P2O5-R2O glasses were prepared by a high-temperature melting method.Analytical-grade raw materials were weighed according to the designed composition and thoroughly mixed.The mixture was melted at 1400 ℃ for 1 h,followed by rapid quenching in deionized water to obtain crushed glass.The crushed glass was ground in a ball mill to obtain glass powders with a median particle size(D50)of 2-3 μm.The glass powder was mixed with solvent and binder to make the slurry,and then the slurry was casted into green tapes.The glass powder was mixed with Al2O3 powder in a mass ratio of 45∶55 and casted into LTCC green tapes.Glass and LTCC green tapes both were cut,stacked,and laminated to form green blocks,which were subsequently sintered into dense ceramics. The structure of the base glass was characterized by solid-state nuclear magnetic resonance spectroscopy(NMR)and Raman spectroscopy.The thermal behavior of the samples was detremined by differential scanning calorimetry(DSC).The phase composition of the sintered samples was identified by X-ray diffraction(XRD).The microstructure of the samples was determined by scanning electron microscopy(SEM).The porosity was quantified by processing the microstructural images via a software named ImageJ.The dielectric constant and dielectric loss of the samples at 5 GHz were measured by a vector network analyzer. Results and discussion The LBCP glass network consists of low-polymerization borate and phosphate groups.The introduction of alkali metal oxides further disrupts the glass network,increasing the proportion of small depolymerized borate and phosphate groups,while reducing the overall network polymerization degree.The LBCP glass exhibits a great crystallization due to the weakened integrity of the glass network and the enhanced short-range ordering induced by high-field-strength La3+ions.In sintering at 850 ℃,the LBCP glass crystallizes abundant crystalline phases LaBO3,CaB2O4,and LaPO4.The introduction of alkali metal oxides further enhances crystallization,reducing the activation energy for crystallization and lowering both crystallization and polymorphic transition temperatures,without altering the types of crystalline phases.Note that Li2O demonstrates a greater effect on promoting glass crystallization,compared to Na2O.This great crystallization promotes more complete growth of crystals LaBO3 and LaPO4,and the dielectric constant and dielectric loss decrease.The great crystallization behavior results in an increased porosity in glass sintering. The LBCP glass/Al2O3 composite precipitates multiple crystalline phases LaBO3,LaPO4,and CaAl2(BO3)2O after sintering.During sintering,CaB2O4 reacts with Al2O3 to form CaAl2(BO3)2O,resulting in the disappearance of CaB2O4.The Al2O3 particles increase the resistance to densification shrinkage,leading to a higher porosity.The sintered composite samples exhibit superior dielectric properties due to the high content of Al2O3 and CaAl2(BO3)2O.The introduction of Na2O enhances mass transport,promoting CaAl2(BO3)2O precipitation and further reducing both the dielectric constant and loss.In contrast,Li2O addition causes a premature crystallization,increasing glass viscosity and hindering CaAl2(BO3)2O formation,thereby deteriorating dielectric performance.The optimization of sintering conditions indicates that CaAl2(BO3)2O precipitation occurs at a heating rate of 2 ℃/min,achieving optimal dielectric properties(i.e.,εr of 6.70 and tan δ of 0.80× 10-3). Conclusions The glass network of LBCP glass consisted of low-polymerized borate and phosphate groups,exhibiting a great crystallization.LBCP glass crystallizes LaBO3,LaPO4 and CaB2O4 when sintered at 850 ℃.Introducing alkali metal oxides further depolymerized the glass network,enhancing a crystallization behavior with an improved grain growth,reducing both dielectric constant and dielectric loss.However,this greater crystallization also increased the porosity of the sintered glass.After sintering,the LBCP glass/Al2O3 composite material precipitates a variety of crystal phases,mainly including LaBO3,LaPO4 and CaA12(BO3)2O.High contents of Al2O3 fillers and CaAl2(BO3)2O phase could improve the dielectric properties of the sintered composites.The addition of Na2O promoted CaAl2(BO3)2O formation,thereby reducing both the dielectric constant and dielectric loss of sintered composites.In contrast,Li2O addition induced a premature crystallization,increasing glass viscosity of the glass phase and inhibiting CaAl2(BO3)2O formation,thereby elevating dielectric loss.Optimizing the heating rate to 2 ℃/min could facilitate complete sintering and maximize CaAl2(BO3)2O content,yielding LTCC materials with optimal dielectric properties(i.e.,εr of 6.70 and tan δ of 0.80×10-3).关键词
镧硼玻璃/低温共烧陶瓷/介电性能/复相陶瓷Key words
lanthanum borate glass/low-temperature co-fired ceramic/dielectric property/multiphase ceramic分类
化学化工引用本文复制引用
曹禹,徐博,韩滨,朱宝京,吕子彬,陈玮,王衍行,祖成奎..La2O3-B2O3-CaO-P2O5玻璃/Al2O3复合低温共烧陶瓷材料介电性能优化[J].硅酸盐学报,2025,53(10):2841-2853,13.基金项目
国家自然科学基金(52202030). （52202030）
