Keywords : grain growth

Low Resistance and High Electromigration Lifetime of Cu-To-Cu Joints Using (111)-Oriented Nanotwinned Copper

Jing-Ye Juang; Kai Cheng Shie; Yu Jin Li; K. N. Tu; Chih Chen

Advanced Materials Letters, 2021, Volume 12, Issue 8, Pages 1-4
DOI: 10.5185/amlett.2021.081654

Cu-to-Cu joints of 30 mm in diameter were fabricated using (111)-oriented nanotwinned copper at 300 °C for 20 min in N2 ambient. The joints possess excellent electrical properties. The average resistance and specific contact resistivity are 4.1 mΩ and 3.98 × 10 -8 Ω·cm 2 , respectively for an as-fabricated Cu joint. With a second step annealing at 400 °C, the resistance can be reduced to 3.27 mΩ due to grain growth across the joint interface. There is 50% resistance reduction compared to SnAg solder joints with the same diameter. The electromigration lifetime for Cu-to-Cu joints is at least 750 times longer than solder joints.

Isothermal aging characteristics of rare earth magnesium hexaaluminate based advanced thermal barrier coatings

Premanshu Jana; Santanu Mandal;Koushik Biswas; Ponnarassery S Jayan

Advanced Materials Letters, 2018, Volume 9, Issue 5, Pages 375-382
DOI: 10.5185/amlett.2018.1674

The isothermal aging characteristics of rare earth magnesium hexaaluminate (REMHA) based thermal barrier coatings (TBC) such as lanthanum magnesium hexaaluminates (LMHA), Neodymium doped LMHA (LNMHA) and LNMHA-Yttrium aluminium garnet (YAG) composite were evaluated at 1400 °C and compared with standard yttria stabilized zirconia (YSZ) coating. The platelet structure of hexaaluminate forms meso-porous structure and provides superior sintering resistance than YSZ coating. Faster grain growth kinetics is observed in YSZ coating as compared to hexaaluminate-based coatings. As a result, the mechanical properties of YSZ coating deteriorate severely whereas hexaaluminate based coating remains almost unaltered. The LNMHA coating is found to be the best sintering resistance among them. LNMHA and LNMHA-YAG composite have potential to meet the requirement of advanced TBC operating even at 1400 °C. 

Crystallization And Grain Growth Behavior Of La2O3-doped Yttria-stabilized Zirconia

Bulent Aktas; Suleyman Tekeli; Serdar Salman

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 260-264
DOI: 10.5185/amlett.2014.amwc1011

The effect of La2O3 addition on the microstructure and grain growth behavior of yttria-stabilized zirconia (8YSZ) was investigated. To this end, 8YSZ was doped with 1–15 wt% La2O3 by means of colloidal processing, and then sintered at 1550 °C for 1 h. XRD results identified a dissolution limit of 5 wt% La2O3 in 8YSZ, the insoluble La2O3 at higher concentrations reacting with ZrO2 during sintering to form a secondary La2Zr2O7 phase. Both undoped and La2O3-doped 8YSZ specimens were annealed at 1400, 1500, and 1600 °C for 10, 50, and 100 h to induce grain growth. Grain growth measurement results showed that an increase in annealing temperature and holding time caused to grain growth in all specimens. Excessive grain growth was observed in the case of the undoped, and 1-5 wt% La2O3-doped 8YSZ specimens; however, the grain growth in 10 and 15 wt% La2O3-doped 8YSZ was inhibited by the formation of a pyrochloric La2Zr2O7 secondary phase around the grains and grain boundaries of 8YSZ. Grain growth exponent (n) and activation energy (Q) values for grain growth of undoped 8YSZ were obtained as 3, and 358 kJ/mol, respectively, while 15 wt% La2O3 containing specimens had a grain growth exponent of 3, and activation energy of 413 kJ/mol. These results indicate that grain growth rate can be controlled by the addition of 10 or 15 wt% La2O3.