سنتز بورنيت (4 Cu5 FeS) ﻧﺎﻧﻮﺳﺎﺧﺘﺎر ﺑﺎ روش آﻟﯿﺎژﺳﺎزي ﻣﮑﺎﻧﯿﮑﯽ و ﺑﺮرﺳﯽ اﺛﺮ دوپ ﮐﺮدن ﻫﻢ زﻣﺎن Zn و Co ﺑﺮ روي ﺧﻮاص ﺗﺮﻣﻮاﻟﮑﺘﺮﯾﮑﯽ آن

Synthesis of nanostructured bornite by mechanical alloying and investigate the effect of co-doping Zn and Co on its thermoelectric properties

ﺑﺮاي ﺗﻮﺳﻌﻪ دﺳﺘﮕﺎهﻫﺎي ﺣﺎﻟﺖ ﺟﺎﻣﺪ ﺗﺮﻣﻮاﻟﮑﺘﺮﯾﮏ، ﻣﻮادي ﺑﺎ ﺑﺎزده ﺑﺎﻻ ﮐﻪ از ﻋﻨﺎﺻﺮ ﻏﯿﺮ ﺳﻤﯽ و ﻓﺮاوان در ﭘﻮﺳﺘﻪ زﻣﯿﻦ ﺗﺸﮑﯿﻞ ﺷﺪه ﺑﺎﺷﺪ از اﻫﻤﯿﺖ ﺑﺴﺰاﯾﯽ ﺑﺮﺧﻮردار اﺳﺖ. در اﯾﻦ ﻣﻘﺎﻟﻪ، ﺧﻮاص ﺗﺮﻣﻮاﻟﮑﺘﺮﯾﮏ ﻧﻤﻮﻧﻪﻫﺎي ﻧﺎﻧﻮﺳﺎﺧﺘﺎر 0.06 ≤ Cu5-2xZnxCoxFeS4 0 ≤ x ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر، اﺑﺘﺪا ﻧﺎﻧﻮذرات Cu5-2xZnxCoxFeS4 ﺗﻮﺳﻂ آﺳﯿﺎب ﮔﻠﻮﻟﻪاي ﭘﺮاﻧﺮژي ﺳﻨﺘﺰ ﺷﺪ و ﺳﭙﺲ ﻧﻤﻮﻧﻪﻫﺎي ﻧﺎﻧﻮﺳﺎﺧﺘﺎر دﯾﺴﮑﯽ ﺷﮑﻞ ﺑﺎ ﭘﺮس داغ ﺗﻬﯿﻪ ﺷﺪ. روش ﭘﺮاش اﺷﻌﻪ اﯾﮑﺲ )XRD( ﺑﺮاي ﻣﻄﺎﻟﻌﻪ ﺧﻮاص ﺳﺎﺧﺘﺎري، ﻣﯿﮑﺮوﺳﮑﻮپ اﻟﮑﺘﺮوﻧﯽ روﺑﺸﯽ )SEM( و ﻣﯿﮑﺮوﺳﮑﻮپ اﻟﮑﺘﺮوﻧﯽ ﻋﺒﻮري )TEM( ﺑﺮاي ﺑﺮرﺳﯽ رﯾﺰﺳﺎﺧﺘﺎر ﻧﻤﻮﻧﻪﻫﺎ ﻣﻮرد اﺳﺘﻔﺎده ﻗﺮار ﮔﺮﻓﺖ و ﺧﻮاص ﺗﺮﻣﻮاﻟﮑﺘﺮﯾﮏ ﻧﻤﻮﻧﻪﻫﺎ ﻧﯿﺰ ﺑﺎ اﻧﺪازهﮔﯿﺮي رﺳﺎﻧﺎﯾﯽ اﻟﮑﺘﺮﯾﮑﯽ و ﻫﺪاﯾﺖ ﺣﺮارﺗﯽ ﺑﺮرﺳﯽ ﺷﺪ. نتايج XRD نشان داد كه ساختار بلوري نمونه‌هاي Cu5-2xZnxCoxFeS4 تا حد دوپ كردن x = 0.04 بورنيت خالص است. ضريب توان نمونه‌هاي بورنيت دوپ نشده برابر با mWm-1K-2 0.25 بود و پس از دوپ كردن با Co و Zn كاهش يافت. جايگزين كردن جزئي همزمان كبالت و روي در ساختار بورنيت در محدوده 0.02 ≤ x ≤ 0.04 باعث تغيير رسانايي نمونه به نوع-n شد. به دليل نوسانات جرمي و كرنشي ناشي از دوپ كردن و نانوساختار بودن، هدايت حرارتي بسيار اندك k < 0.30 Wm-1K-1 براي تمام نمونه‌هاي دوپ شده بدست آمد. بيشترين مقدار ZT = 0.35 براي نمونه دوپ شده با مقدار x = 0.06 حاصل شد.

To improve current solid state thermoelectric devices, high performance materials based on safe and abundant elements is required. Here, the thermoelectric properties of Cu5-2xZnxCoxFeS4 (0 ≤ x ≤ 0.06) nanostructured samples were investigated. First, Cu5-2xZnxCoxFeS4 nanoparticles were synthesized by high energy ball milling and then consolidated into pellets by hot pressing. X-ray diffraction (XRD) analysis was employed for structural study, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for microstructural analysis, and the thermoelectric properties were evaluated by electrical conductivity and thermal conductivity measurements. XRD data revealed that the crystal structure of the materials to be consistent with a pure bornite phase up to x = 0.04 for Cu5-2xZnxCoxFeS4. The power factor of un-substituted sample was 0.25 mWm-1K-2 which decrease after Co and Zn substitution. Concurrent substituting of Co and Zn for Cu in the range of 0.02 ≤ x ≤ 0.04 changed the p-type conduction of bornite to n-type at room temperature and up to 527 K. Extremely low thermal conductivities of k < 0.30 Wm-1K-1 were obtained for all double substituted samples as a results of the significant mass and strain field fluctuations and the nanostructured nature of the samples. The highest ZT value of 0.35 was attained for x = 0.06.