熱電材料在溫差發電及熱電致冷方面都具有廣泛的應用，而陶瓷的熱電材料具有無噪音、無污染等之優點，是深受期待的材料。SrTiO3 系陶瓷是中高溫區(400~1000 K) 熱電發電中最應被研發的熱電材料，其 ZT 值的研究主要集中在兩個方向：一是藉由增加材料內部的載子濃度(carrier concentration)來提高其功率因子 (electrical power factor, S2σ)，二是增加材料內部的聲子 (phonon) 散射來降低其熱導係數，且不使電傳導係數下降太多。
為獲得次微米晶粒含釔之SrTiO3塊材，本研究以有機前導物法(Polymerized Complex method)製備含釔之SrTiO3陶瓷粉體，於 1050℃~1200℃及壓力30 MPa下進行火花電漿燒結 (SPS, spark plasma sintering)。燒結體塊材的熱電性質是以ZEM-3量測，粉體及燒結體的微結構是以 XRD、FE-SEM、EDS 等儀器分析，依此，了解釔含量及燒結溫度對於燒結體的顯微結構及熱電性質影響。
研究結果顯示，經925℃/4.5 h 鍛燒合成含釔之SrTiO3粉體，其粉末顆粒大小約為 100 nm; 經SPS 於1150及1200℃ 燒結5 min的塊材，其相對密度分別達96及 97 %。SPS 於1150及1200℃ 下燒結的塊材其破斷面經拋光熱腐蝕可看出晶粒大小分別為1 ~ 2μm及0.5μm。
在熱電性質方面，隨著釔含量及燒結溫度的增加，其電傳導係數有提升的趨勢，然而，Seebeck 係數則呈現相反之趨勢。最佳電傳導係數為1200℃ SPS 燒結所得含6 mol% 釔之試片，其量測溫度685 K時為70.83 S/cm，最大功率因子值則為 570 μw/mK2。SPS在1150℃燒結下所得含釔量0 mol% 之SrTiO3 燒結體具有最佳的Seebeck 係數於956 K溫區間可得 -435.10μV/K。

Thermoelectric materials and devices have widely used in the fields of energy conversion, sensors, and thermoelectric cooling. The ceramic thermoelectric materials are also well-known for no noise and no pollution. SrTiO3 is commonly used in the temperature range of 400-1000 K in thermoelectric materials systems. The research for figure-of-merit (ZT) has mainly focused on two main areas: (1) Improving the electrical power factor by increasing the material’s carrier concentration; (2) Lowering thermal conductivity by increasing the material’s ability to scatter phonons without causing a major decrease in electrical conductivity.
Preparing the sub-micron Y-doped SrTiO3 bulks, we use Polymerized Complex method to acquire Y-doped SrTiO3 powders. A series of powders were sintered by spark plasma sintering system (SPS). The microstructure of Y-doped SrTiO3 powders and bulks were analyzed by XRD、FE-SEM、EDS. Finally, our research investigates how the Y content and sintering temperature influence the SrTiO3 bulks’ microstructure and thermoelectric properties.
The findings show that the Particle size of Y-doped SrTiO3 powders calcined at 925℃/4.5 h is around 100 nm. The powders SPS at 1150℃ and 1200℃ for 5 min, can attain the relative densities of Y-doped SrTiO3 bulks for 96 % and 97% respectively. The polished thermal etched surface of Y-doped SrTiO3 specimen sintered by SPS at 1150℃ and 1200℃, which grain size are 1 ~ 2μm and 0.5μm.
In terms of thermoelectric properties, the electrical conductivity increases with the increasing Y content and sintering temperature. However, the Seebeck coefficient shows the opposite trend. The maximum electrical conductivity is the specimen of Y-doped SrTiO3 (6 mol%) SPS at 1200℃, which can attain 70.83 S/cm at 685 K. The maximum power factor is 570 μw/mK2, and the best Seebeck coefficient is the specimen of Y-doped SrTiO3 (0 mol%) SPS at 1150℃, which attains -435.10 μV/K at 956 K.

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