With the advantages of material-saving shapable production and facile geometry design, shapable methods provide a broad prospect for the future thermoelectric material production. Herein, cold spraying followed by annealing (CSA) induces enriched defects in the bulk material, which can lead to excellent thermoelectric performance and hardness. Compared with the HP process, CSA contributes to more pores and intrinsic defects. The enriched intrinsic defects contribute to moderate electrical performance. Simultaneously, these defects strongly scatter phonons, leading to ultra-low total thermal conductivity values of similar to 0.64 W m-1 K-1 for both p-type CSA Bi0.5 Sb1.5 Te3 and n-type CSA Bi2 Te2.7 Se0.3 bulks at room temperature. Correspondingly, CSA bulks possess excellent room-temperature zT of similar to 1.1 (p-type Bi0.5 Sb1.5 Te3 ) and similar to 0.9 (n-type Bi2 Te2.7 Se0.3 ), respectively, which are comparable to those prepared by HP and other shapable methods. Furthermore, a four-leg thermoelectric device is assembled based on as-prepared ptype CSA Bi0.5 Sb1.5 Te3 and n-type CSA Bi2 Te2.7 Se0.3 bulks, achieving a rational energy conversion efficiency of similar to 4% under a small temperature difference of 100 K. This study demonstrates CSA method is promising for future shapable production of high-performance thermoelectric materials. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

CrSi2-based thermoelectric materials with high earth abundance, low material cost, and high stability, have attracted increasing research interests. However, their performance is till off the practical application level because of high lattice thermal conductivity. Here, we discovered that the observed dispersive localized Ta-rich area and Ta substitution in the CrSi2 matrix induce significant lattice distortions and strain fields, leading to strengthened phonon scattering and in turn an ultralow lattice thermal conductivity of -0.87 W m-1 K-1 at -750 K in the Cr0.94Ta0.06Si2. Together with a power factor of -7 mu W cm-1 K-2 at -750 K, a relatively high figure of merit of 0.28 at -750 K is observed in the Cr0.94Ta0.06Si2. This figure of merit is comparable to other state-of-the-art CrSi2-based thermoelectric materials. Our understanding on the dispersive localized Ta-rich area and Ta substitution can be used to guide the development of wide thermoelectric materials.

BiFeO3 bulk ceramics were prepared by sol-gel auto-combustion method at the temperature of 725 degrees C?750 degrees C?775 degrees C?800 degrees C?825 degrees C respectively (abbreviated as C725, C750, C775, C800 and C825). XRD patterns confirm the phase stability of BFO ceramics in a large temperature range from 725 degrees C to 825 degrees C. Almost no pores were observed in the compact C775 ceramic which has the highest density (8.05 g/cm(3), 96.83% of the theoretical one) compared to that of other samples. The average grain sizes of the BFO ceramics increased with the increasing of sintering temperature. The highest electric resistance (538K omega at 50 Hz) and lowest dielectric constant (689.01 at 1 kHz) were obtained in C775. All BFO bulk ceramics exhibit strong optical absorption in the visible range with two absorption peaks at 520-538 nm and 670 nm. Band gaps of the as-prepared BFO ceramics were slightly affected by sintering temperature, since the band gaps of C725, C750, C775, C800, C825 are 2.74 eV, 2.78 eV, 2.76 eV, 2.63 eV, 2.75 eV, respectively. The weakest photoluminescence signal with largest red shift can be observed in C775.

A series of Si-rich and Si-deficient materials with nominal composition CoSi x ( x = 1.05, 1.00, 0.95, 0.90) have been synthesized by arc melting and hot-pressing sintering. The effects of nonstoichiometry on the phase composition and thermoelectric properties were systematically investigated. All the materials are composed of main phase CoSi, while trace impurity phase Co 2 Si or CoSi 2 was detected in the nonstoichiometric materials. Transport measurements revealed that the Seebeck coefficient was remarkably decreased and the electrical conductivity was increased due to the significant enhancement in carrier concentration, and the lattice thermal conductivity was almost unchanged. As a result, a serious reduction in ZT was found in the nonstoichiometric materials because of the deteriorated power factor. This work demonstrates that a slight deviation from stoichiometric composition in CoSi-based material would cause a seriously detrimental influence on thermoelectric performance due to the dramatical decrease in Seebeck coefficient.

采用电弧熔炼及热压烧结方法制备了MoSi2热电材料,对样品的形貌、相结构和热电性能进行了分析.结果 表明:所得样品为单相MoSi2.Seebeck系数随温度的升高,在300～650K下降,在650～873 K内上升.电导率、热导率随着温度的升高都逐渐降低.热电功率因子和ZT值在测试温度范围内先降后升,在780K时Z7T值达到最大值0.01.

The Bi0.5Sb1.4−xNaxIn0.1Te3 (x = 0.02–0.20) alloys were fabricated by high vacuum melting and hot-pressing technique. The phase structures and morphology of the bulk samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Effects of In and Na co-doping on the electrical and thermal transport properties were studied from room temperature to 500 K. Seebeck coefficient of the Bi0.5Sb1.5Te3 can be enhanced by substituting Sb with In and Na at near room temperature. The electrical conductivity of the In and Na co-doped samples is lower than that of the Bi0.5Sb1.5Te3 alloy from room temperature to 500 K. In and Na co-doping of appropriate percentage optimizes the thermal conductivity of the Bi0.5Sb1.5Te3 alloy. The minimum value of thermal conductivity of Bi0.5Sb1.36Na0.04In0.1Te3 alloy is 0.45 W·m−1·K−1 at 323 K, which leads to a great improvement in the thermoelectric figure of merit (zT). The maximum zT value reaches 1.42 at 323 K.

The Bi 0.5 Sb 1.4− x Na x In 0.1 Te 3 ( x = 0.02–0.20) alloys were fabricated by high vacuum melting and hot-pressing technique. The phase structures and morphology of the bulk samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Effects of In and Na co-doping on the electrical and thermal transport properties were studied from room temperature to 500 K. Seebeck coefficient of the Bi 0.5 Sb 1.5 Te 3 can be enhanced by substituting Sb with In and Na at near room temperature. The electrical conductivity of the In and Na co-doped samples is lower than that of the Bi 0.5 Sb 1.5 Te 3 alloy from room temperature to 500 K. In and Na co-doping of appropriate percentage optimizes the thermal conductivity of the Bi 0.5 Sb 1.5 Te 3 alloy. The minimum value of thermal conductivity of Bi 0.5 Sb 1.36 Na 0.04 In 0.1 Te 3 alloy is 0.45 W·m −1 ·K −1 at 323 K, which leads to a great improvement in the thermoelectric figure of merit ( zT ). The maximum zT value reaches 1.42 at 323 K.

采用钽管封装熔炼和热压烧结技术制备了BaxCa(2-x)Si (x=0,0.01,0.03,0.05)热电材料.利用X射线衍射对样品的物相结构进行表征.在300～873 K内研究了该试样的热电性能.结果表明,BaxCa(2-x)Si块体材料的XRD图谱与Ca2Si的XRD图谱对应一致,但所有样品中都出现了Ca的衍射峰.当Ba掺杂量为0.03和0.05时,样品BaxCa(2-x)Si中还出现了BaSi杂相.随着Ba掺杂浓度的增加,电导率逐渐减小,塞贝克系数则缓慢增加.在300～873 K内,BaxCa(2-x)Si(x=0.01)的热导率都低于Ca2Si的热导率.在550～873 K,Bax Ca(2-x)Si (x=0.01)表现了较高的热电优值ZT,在873 K时的最大ZT值为0.17.

采用真空熔炼和热压烧结技术制备了Al掺杂P型Bi0.5Sb1.5Te3热电材料.样品的物相结构和形貌分别采用X射线衍射(XRD)和扫描电镜(SEM)进行表征.结果表明,AlxBi0.5Sb(1.5-x)Te3(x=0,0.04,0.08,0.12)块体材料的XRD图谱与Bi0.5Sb1.5Te3的XRD图谱对应一致.该复合材料的组织致密,且层状结构特征明显.Al部分替代Sb后,优化了载流子浓度,从而提高了材料的电导率.在室温附近所有掺杂样品的热导率都低于Bi0.5Sb1.5Te3样品的热导率,从而有效改善了材料的热电性能.其中,AlBi0.5Sb(1.5-x)Te3 (x=0.04)在室温附近表现了最低的热导率,320 K时获得最大ZT值(为1.0).

Ca(2−x)AgxSi (0 ≤ x ≤ 0.1) with 47.5% excess of Ca alloys were fabricated by melting in a tantalum tube and hot pressing technique. Phase structures of the samples were studied by means of x-ray diffraction. The electrical conductivity and Seebeck coefficient of Ca(2−x)AgxSi alloys were studied in the temperature range of 300–873 K. The electrical conductivity of the Ag-doped samples increases within the whole test temperature range. All samples show p-type semiconductor behavior. The electrical conductivity decreases with increasing temperature from 300 K to 873 K, which is typically observed for a degenerate semiconductor. Compared with the undoped samples, Ag-doping (x = 0.04–0.1) results in decreases of Seebeck coefficient, especially Ca(2−x)AgxSi with x = 0.1. The thermal conductivity of the doped samples gradually increases with increasing the Ag-doping content. The Ca(2−x)AgxSi with x = 0.02 sample exhibits the lowest thermal conductivity within the whole test temperature range. The ZT values of Ca(2−x)AgxSi with x = 0.02 sample have an enhancement in the temperature range of 300–873 K by contrast with those of the Ca2Si sample. The maximum ZT value is 0.16 at 837 k, which is observed for the Ca(2−x)AgxSi with x = 0.04 sample.

Ca2Si(1-x)Snx (x=0, 0.02, 0.04, 0.06) thermoelectric materials were fabricated by melting in tantalum tube and hot pressing technique.Phase structures of the samples were analyzed by means of x-ray diffraction (XRD).The results show that the characteristic peaks of the bulk Ca2Si(1-x)Snx can be indexed into Ca2Si.The peak of Ca5Si3 exists in the XRD patterns of all the bulk Ca2Si(1-x)Snx samples.The peak of CaSn3 can be found in the XRD patterns of the bulk Ca2Si(1-x)Snx(x=0.06) sample.Hall coefficients of the samples were measured at room temperature.The electrical conductivity and Seebeck coefficient of Ca2Si(1-x)Snx alloys were studied in the temperature range of 300-873 K.The electrical conductivity of the Sn-doped samples increases with increasing Sn concentration, while the Seebeck coefficient of the Sn-doped samples decreases.The lattice thermal conductivity and total thermal conductivity of the Ca2Si(1-x)Snx samples were investigated in the temperature range of 300-873 K.Compared with the Ca2Si sample, Sn-doping (x=0.02, 0.04) results in the decrease of the lattice thermal conductivity, especially Ca2Si(1-x)Snx with x=0.02.The Ca2Si(1-x)Snx with x=0.02 sample exhibits the lowest thermal conductivity within the whole testing temperature range.The ZT values of Ca2Si(1-x)Snx with x=0.02 sample have an enhancement in the temperature range of 550-873 K by contrast with those of the Ca2Si sample.The maximum ZT value was 0.22 at 873 k, which was observed for the Ca2Si(1-x)Snx with x=0.02 sample.

采用真空熔炼及热压方法制备Ga和Na共掺杂Bi0.5Sb1.5Te3热电材料.利用X射线衍射(XRD)技术对样品的物相结构进行了表征.在300～ 500 K测量温度范围内,共掺杂样品的Seebeck系数均低于Bi0.5Sb1.5Te3的Seebeck系数,并随着Ga掺杂量的增加,Seebeck系数逐渐减小.共掺杂使样品的载流子浓度增加,从而有效地提高了材料的电导率.所有共掺杂样品的热导率都大于Bi0.5Sb15Te3的热导率,在Na掺杂浓度不变的情况下,随着Ga掺杂浓度的增加,热导率逐步增加,Na0.04Bi0.5Sb1.46-xGaxTe3(x=0.12)样品具有高电导率的同时,Seebeck系数和热导率的损失不是很大,材料的热电性能得到了改善,在300～ 475 K测量温度范围内的热电性能优值与Bi0.5Sb1.5Te3相比较均有所提高,325 K时的最大ZT值为1.4.

Ga and K dual doped Bi0.5Sb1.5Te3 thermoelectric materials were prepared by vacuum melting and hot pressing. XRD results indicate that all the characteristic peaks of the bulk Ga0.02Bi0.5Sb1.48-xKxTe3 can be indexed into Bi0.5Sb1.5Te3, but the diffraction peaks of the dual doped samples slightly lean to the left. Hot-pressed bulk materials exhibit the (001) preferred orientation. SEM morphology shows that microstructure is dense and layered structure. The Seebeck coefficient of Bi0.5Sb1.5Te3 near the room temperature can be improved to some extent by Ga and K dual doping. The electrical conductivity of dual doped samples can be improved in different degrees, and electrical conductivity of Ga0.02Bi0.5Sb1.42K0.06Te3 samples is improved obviously. In the whole measured temperature range of 300-500 K, the thermal conductivity of the dual doped samples is higher than that of Bi0.5Sb1.3Te3. ZT values of the dual doped samples are improved at near 300 K, and the ZT value of Ga0.02Bi0.5Sb1.42K0.06Te3 sample reaches 1.5 at 300 K.

采用真空熔炼及热压方法制备Ga和Na共掺杂Bi0.5Sb1.5Te3热电材料。利用X射线衍射（XRD）技术对样品的物相结构进行了表征。在300~500K测量温度范围内,共掺杂样品的Seebeck系数均低于Bi0.5Sb1.5Te3的Seebeck系数,并随着Ga掺杂量的增加,Seebeck系数逐渐减小。共掺杂使样品的载流子浓度增加,从而有效地提高了材料的电导率。所有共掺杂样品的热导率都大于Bi0.5Sb1.5Te3的热导率,在Na掺杂浓度不变的情况下,随着Ga掺杂浓度的增加,热导率逐步增加,Na0.04Bi0.5Sb1.46-xGaxTe3（x=0.12）样品具有高电导率的同时,Seebeck系数和热导率的损失不是很大,材料的热电性能得到了改善,在300~475K测量温度范围内的热电性能优值与Bi0.5Sb1.5Te3相比较均有所提高,325K时的最大ZT值为1.4。

Bi(2−x)GaxTe2.7Se0.3 (x=0, 0.04, 0.08, 0.12) alloys were fabricated by vacuum melting and hot pressing technique. The structure of the samples was evaluated by means of X-ray diffraction. The peak shift toward higher angle can be observed by Ga-doping. The effects of Ga substitution for Bi on the electrical and thermal transport properties were investigated in the temperature range of 300–500K. The power factor values of the Ga-doped samples are obviously improved in the temperature range of 300–440K. Among all the samples, the Bi(2−x)GaxTe2.7Se0.3 (x=0.04) sample showed the lowest thermal conductivity near room temperature and the maximum ZT value reached 0.82 at 400K.

Na and Ga co-doped n-type Bi2Te2.7Se0.3thermoelectric materials were synthesized by vacuum melting and hot pressing methods.XRD results indicate that all the characteristic peaks of the bulk Na0.04Bi1.96-xGaxTe2.7Se0.3can be indexed into those of the bulk Bi2Te2.7Se0.3.Compositional analysis of the bulk Na0.04Bi1.96-xGaxTe2.7Se0.3was carried out by energy dispersive analysis of X-rays(EDAX),in which no oxidation was detected.Electrical and thermal transport properties of the samples had been measured along the the direction perpendicular to the hot-pressing direction in the temperature range of 298-523 K.Na and Ga codoping can enhance the carrier concentration,and accordingly the electrical conductivity as well.The Seebeck coefficients of the co-doped samples have different degree of loss.Due to the decrease of lattice thermal conductivity,Na-doped and Na and Ga co-doped Na0.04Bi1.96-xGaxTe2.7Se0.3(x=0.04)samples can reduce the thermal conductivity.Thermal conductivity of the Na0.04Bi1.96-xGaxTe2.7Se0.3increases gradually with the increase of Ga-doping.Na and Ga co-doped Na0.04Bi1.96-xGaxTe2.7Se0.3(x=0.04)samples lead to a great improvement in the thermoelectric figure of merit ZT.The highest ZT of the sample can reach 0.75 at 398K.

Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0, 0.02, 0.04, 0.06) and Bi 2 Te 2.7 Se 0.3 alloys were prepared by vacuum melting and hot pressing methods. The phase structure of the bulk samples were characterized by X-ray diffraction. Effects of indium and sodium co-substitutions for bismuth on the electrical and thermal transport properties were investigated in the temperature range of 298–473 K. Indium and sodium co-doping can enhance the carrier concentration, and accordingly the electrical conductivity can be improved effectively. The Seebeck coefficients of the co-doped samples have not been derogated strongly. The power factors are enhanced for the Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0.02) within the whole testing temperature range. The Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0.02) samples have the lower thermal conductivity due to reduction in lattice thermal conductivity, which leads to a great improvement in the thermoelectric figure of merit ZT. The highest ZT of the sample can reach 0.87 at 398 K.

N-type Bi2Te2.7Se0.3 thermoelectric materials with Ga and K dual doping were synthesized by vacuum melting and hot pressing. XRD results indicate that Ga and K elements have been completely dissolved into the crystal structure of Bi2Te2.7Se0.3. The single-phase solid solution alloy has been formed. SEM results show that the bulk samples are compact with the laminated structure. Ga and K dual doping increases the Seebeck coefficient of Bi2Te2.7Se0.3 through Ga and K partial substitution of Bi in the most range of 300 similar to 500 K, while the electrical conductivity of the dual doped samples is improved. The thermal conductivity of the dual doped samples is higher than that of Bi2Te2.7Se0.3. The maximum ZT value reaches 1.05 at 500 K for Ga0.02Bi1.94K0.04Te3Se0.3 sample.

The Bi0.5Na0.02Sb1.48−x In x Te3 alloys (x = 0.02–0.20) were synthesized by vacuum melting and hot pressing methods at 753 K, 60 MPa for 30 min. Effects of Na and In dual partial substitutions for Sb on the thermoelectric properties were investigated from 300 to 500 K. Substituting Sb with Na and In can enhance the Seebeck coefficient effectively near room temperature. The electrical resistivity of the Na and In dual-doping samples is higher within the whole test temperature range. The Bi0.5Na0.02Sb1.48−x In x Te3 samples (x = 0.02, 0.06) play a great role in optimizing the thermal conductivity. As for the Bi0.5 Na0.02Sb1.46In0.02Te3 alloy, the minimum value of thermal conductivity reaches 0.53 W·m−1·K−1 at 320 K. The thermoelectric performance of the Na and In dual-doped samples is greatly improved, and a figure of merit ZT of 1.26 is achieved at 300 K for the Bi0.5Na0.02Sb1.42In0.06Te3, representing 26 % enhancement with respect to ZT = 1.0 of the undoped sample.