Mg2Si及Zn4Sb3熱電模組固液擴散接合擴散阻障層及ZnSb熱電薄膜研究

Diffusion Barrier of Mg2Si and Zn4Sb3 Thermoelectric Modules Solid-Liquid Interdiffusion Bonding and ZnSb Thermoelectric thin film

許世文(Shih-Wen Hsu)

指導教授 ： 莊東漢

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2021年)

https://doi.org/10.6342/NTU202103866

摘要

綠色環保為現今大家所重視的議題，透過使用再生能源來取代非再生能源，以減緩地球資源的快速消耗。熱電材料因本身的特性，能藉由外在環境的冷熱差異，將熱能轉換為電能，所產生的廢熱再回收利用，達到能源永續再生的理念。
本研究選用中溫熱電材料Zn4Sb3及Mg2Si為母材，分別以Ag和Sn作為高熔點及低熔點金屬材料，由Ni和Ti基金屬玻璃當作擴散阻障層，再以固液擴散接合的方式與Cu金屬接合，並且透過高溫儲存實驗，評估使用Ni和Ti基金屬玻璃當作擴散阻障層後的熱電模組壽命。
研究結果顯示，只有鍍一層Ni層當作擴散阻障層的Mg2Si中溫熱電模組其附著性比預鍍Sn後再鍍製Ni層的結果來的好，將Mg2Si中溫熱電模組放置於高溫400℃的環境1500小時後，其顯微結構仍然保持完整且無損壞現象。將Ti/WTi/Ti金屬玻璃薄膜複合層當作Mg2Si中溫熱電模組擴散阻障層，也可有效防止金屬間相互的擴散，能在高溫400℃下承受1500小時。然而對於Zn4Sb3中溫熱電模組結果顯示，以Ti/WTi/Ti金屬玻璃薄膜複合層當作擴散阻障層，在高溫400℃的環境下只能承受250小時，隨著時間的增長，擴散阻障層無法抵擋金屬間相互擴散，造成Zn4Sb3中溫熱電模組損壞。故此研究發現金屬玻璃薄膜當作中溫熱電模組的擴散阻障層是有效且具可行性。
實驗的另一部分為使用共同濺鍍的方式鍍製不同厚度的ZnSb薄膜，再經由不同溫度進行後退火，探討適合應用的ZnSb熱電薄膜，實驗結果顯示，厚度為500 nm的ZnSb熱電薄膜在退火溫度為350℃時，有良好的ZnSb熱電薄膜性質，其相結構為Zn4Sb3 + ZnSb兩相共存，薄膜載子流濃度為1.16 x 1020 cm-3 及電阻率為5.87 x 10-3 Ωcm，比厚度為100 nm的ZnSb熱電薄膜更適合應用。

關鍵字

熱電材料 ； 固液擴散接合 ； 擴散阻障層 ； 界面反應 ； 熱電薄膜 ； 高溫時效

並列摘要

Nowadays, renewable energy is gaining public attention due to its sustainability, which could reduce the consumption of limited resources on Earth. A major issue is how to make full use of this kind of green energy. Due to the special characteristics of thermoelectric materials, they can convert thermal energy into electrical energy through the difference between cold and heat in the external environment, providing an avenue for sustainable energy regeneration.
In this study, experiments were performed with Zn4Sb3 and Mg2Si, both of which are mid-high temperature thermoelectric materials. Silver was used as a high-melting metal and tin as a low-melting metal. Nickel and titanium-based metallic glasses were used as diffusion barrier layers for bonding with copper by solid-liquid interdiffusion bonding. The performance of a thermoelectric module employing Ni and Ti-based metallic glass as the diffusion barrier layer during thermoelectric operation in a high temperature environment and after high-temperature storage experiments were examined.
The results showed that the adhesion of a Mg2Si thermoelectric module coated with a single nickel diffusion barrier layer was better than that achieved with a pre-coated tin layer, and it could remain intact at a high temperature of 400 °C for 1500 hours. Also, the use of sputtered Ti/WTi/Ti metallic glass film as a diffusion barrier layer allowed the module to be held for more than 1500 hours at 400 °C without intermetallic diffusion occurring.
However, although the Zn4Sb3 thermoelectric material with Ti/WTi/Ti metallic glass film as a diffusion barrier layer maintained integrity under high temperature for 250 hours, the diffusion barrier layer could not resist the interdiffusion between metals, which would cause damage to the thermoelectric module during extended service. This study finds that the application of Ti-based metallic glass material as a diffusion barrier layer is effective and feasible.
The experimental results showed that, in ZnSb thermoelectric films with a thickness of 500 nm annealed at 350 °C, the carrier concentration of the film was 1.16 x 1020 cm-3 and the electrical resistivity was low, 5.87 x 10-3 Ωcm. The good properties of ZnSb thermoelectric film can be ascribed to the phase structure being a mixture of Zn4Sb3 and ZnSb. Therefore, for application, ZnSb thermoelectric film of 500 nm thickness is better than that of 100 nm thickness.

並列關鍵字

Thermoelectric materials ； Solid-Liquid interdiffusion bonding ； Diffusion barrier ； Interfacial reaction ； Thermoelectric film ； Annealing

參考文獻

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