本研究利用溶膠凝膠法製備厚度約800nm的(Na0.5K0.5)NbO3 壓電薄膜，透過以下三種方法改善其結晶性：(1) 優化熱處理條件、(2) 不同摻雜元素比例以及(3) 添加緩衝層，探討壓電薄膜的機械性質與電性能的影響，包括XRD、SEM、EDS、εr、tanδ、P-E、d33等，找出最佳的材料參數。此外，透過電卡效應的量測，評估其應用於微機電系統(Micro Electro Mechanical Systems, MEMS) 力感測器的潛力。
首先，本研究發現以升溫速率30°C/s，退火溫度為660°C下退火5分鐘的條件下，可達到最佳的薄膜品質。EDS分析顯示(Na+K)/Nb的比例接近理論值1，表現出最佳的 KNN 晶相。第二階段透過摻雜Li元素於KNN晶格的A-site ，有效的改善因高溫而揮發的Na、K離子空缺，在摻雜量為0.06 mol% 時，獲得電性質良好的LKNN薄膜，其在頻率1 kHz下介電常數εr 為515.88、介電損耗tanδ為0.0493，殘餘極化量Pr為23.85 μC/cm2 ，壓電係數d33為68.2 pm/V。
第三階段透過添加緩衝層HfO2，改善薄膜與基板之間的界面應力，楊氏模量從108.7GPa略微下降至93.5GPa，硬度從5.39 GPa 減少至4.68 GPa，更進一步將材料的壓電係數d33提升至76.81 pm/V，殘餘極化量Pr為26.3 μC/cm2。電卡效應量測曲線顯示，在溫度範圍為328-330K時，材料在相對較低的電場變化範圍表現出最大的電熱響應，ΔT=15.31 K, ΔT/ΔE=0.38 Kmm/kV ，獲得和含鉛材料相近的電熱特性。
相比於傳統的壓電材料PZT，本研究製備的KNN 壓電薄膜具有環保無毒性、高壓電係數、高介電常數、低損耗等優點，在未來無鉛MEMS 高靈敏度的力感測器的領域上具有相當大的潛力。

In this study, (Na0.5K0.5)NbO3 piezoelectric thin films (~800 nm) were prepared using the sol-gel method. The crystallinity of the films was improved through: (1) optimizing heat treatment conditions, (2) varying doping element ratios, and (3) adding a buffer layer. Additionally, the potential application as force sensors in Micro Electro Mechanical Systems (MEMS) were evaluated through electrocaloric effect measurements. X-ray diffraction (XRD) and ferroelectric analysis revealed that KNN thin films under a heating rate of 30°C/s and an annealing temperature of 660°C, exhibited favorable film characteristics. Doping the KNN lattice's A-site with Li (0.06 mol) effectively improved the vacancies of Na and K ions caused by high temperatures, resulting in good electrical properties: dielectric constant (εr) of 515.88, dielectric loss (tanδ) of 0.0493, remnant polarization (Pr) of 23.85 μC/cm², and piezoelectric coefficient (d33) of 68.2 pm/V at 1 kHz. Subsequently, adding a HfO2 buffer layer reduced interfacial stress, slightly decreasing Young's modulus from 108.7 GPa to 93.5 GPa and hardness from 5.39 GPa to 4.68 GPa. Further enhanced the piezoelectric coefficient (d33) to 76.81 pm/V and remnant polarization (Pr) to 26.3 μC/cm². Electrocaloric effect measurement showed that material's largest electrothermal response (ΔT=15.31 K, ΔT/ΔE=0.38 Kmm/kV) occurred within the 328-330K range, comparable to lead-containing materials. It demonstrates significant potential for lead-free, high-sensitivity force sensors in future MEMS applications.

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