Single-crystal samples of type-VIII BasGa16-xCuxSn30 （x = 0, 0.03, 0.06, 0.15） clathrates were prepared using the Sn-flux method. At room temperature the carrier density, n, is 3.5-5 × 10^19 cm^-3 for all the s...Single-crystal samples of type-VIII BasGa16-xCuxSn30 （x = 0, 0.03, 0.06, 0.15） clathrates were prepared using the Sn-flux method. At room temperature the carrier density, n, is 3.5-5 × 10^19 cm^-3 for all the samples, the carrier mobility, μH, increases to more than twice that of BasGa16Sn30 for all the Cu doping samples, and consequently the electrical conductivity is enhanced distinctly from 1.90×10^4 S/m to 4.40 ×10^4 S/m, with the Cu composition increasing from x = 0 to x = 0.15. The Seebeck coefficient,α, decreases slightly with the increases in Cu composition. The values are about 0.72 W/mK at 300 K and are almost invariant with temperature up to 500 K for the samples with x = 0 and x = 0.03. The lattice thermal conductivity, μL, decreases from 0.59 W/InK for x = 0 to 0.50 W/mK for x = 0.03 at 300 K. The figure of merit for x = 0.03 reaches 1.35 at 540 K.展开更多
Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect ...Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect fluid Bianchi type- IX cosmological model is presented since other models doesn’t exist in Brans-Dicke scalar tensor theory of gravitation. Some physical properties of the model are also discussed.展开更多
采用Sn自熔剂法制备了具有n型传导的VIII型Ba8Ga16 xGexSn30(0 x 1.0)单晶笼合物,并对其结构和热电特性进行研究.研究结果表明:Ge在单晶中的实际含量较少,随着掺杂量的增加样品的晶格常数略有减小,Ge掺杂后样品的载流子浓度较掺杂前低,...采用Sn自熔剂法制备了具有n型传导的VIII型Ba8Ga16 xGexSn30(0 x 1.0)单晶笼合物,并对其结构和热电特性进行研究.研究结果表明:Ge在单晶中的实际含量较少,随着掺杂量的增加样品的晶格常数略有减小,Ge掺杂后样品的载流子浓度较掺杂前低,迁移率增加;所有样品的Seebeck系数均为负值,且绝对值较未掺杂样品低,但Ge掺杂后样品的电导率提高了62%;x=0.5的样品在500 K附近取得最大ZT值1.25.展开更多
本文采用Sn自熔剂法,制备Mg掺杂Sn基单晶笼合物Ba8Ga16-XMgXSn30(0 X 1.5),并对其结构及电传输性能进行研究.结果表明所制备化合物为具有空间群Iˉ43m的VIII型单晶笼合物,随Mg掺杂量的增加,对应化合物的熔点略有升高,晶格常数减小,掺杂...本文采用Sn自熔剂法,制备Mg掺杂Sn基单晶笼合物Ba8Ga16-XMgXSn30(0 X 1.5),并对其结构及电传输性能进行研究.结果表明所制备化合物为具有空间群Iˉ43m的VIII型单晶笼合物,随Mg掺杂量的增加,对应化合物的熔点略有升高,晶格常数减小,掺杂样品中填充原子Ba的实际含量低于理想值8.0,其在十二面体空洞中的占有率约为0.93(Mg的名义含量X=1.5时).所有样品均表现为n型传导,Mg的掺入对材料的能带结构有一定影响,Mg掺杂后,样品的载流子浓度降低,Seebeck系数的绝对值、电阻率增加,Mg的名义含量X=1.5时,样品的功率因子在430 K附近取得最大值1.26×10-3W·m-1·K-2.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.50902119)
文摘Single-crystal samples of type-VIII BasGa16-xCuxSn30 （x = 0, 0.03, 0.06, 0.15） clathrates were prepared using the Sn-flux method. At room temperature the carrier density, n, is 3.5-5 × 10^19 cm^-3 for all the samples, the carrier mobility, μH, increases to more than twice that of BasGa16Sn30 for all the Cu doping samples, and consequently the electrical conductivity is enhanced distinctly from 1.90×10^4 S/m to 4.40 ×10^4 S/m, with the Cu composition increasing from x = 0 to x = 0.15. The Seebeck coefficient,α, decreases slightly with the increases in Cu composition. The values are about 0.72 W/mK at 300 K and are almost invariant with temperature up to 500 K for the samples with x = 0 and x = 0.03. The lattice thermal conductivity, μL, decreases from 0.59 W/InK for x = 0 to 0.50 W/mK for x = 0.03 at 300 K. The figure of merit for x = 0.03 reaches 1.35 at 540 K.
文摘Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect fluid Bianchi type- IX cosmological model is presented since other models doesn’t exist in Brans-Dicke scalar tensor theory of gravitation. Some physical properties of the model are also discussed.
文摘采用Sn自熔剂法制备了具有n型传导的VIII型Ba8Ga16 xGexSn30(0 x 1.0)单晶笼合物,并对其结构和热电特性进行研究.研究结果表明:Ge在单晶中的实际含量较少,随着掺杂量的增加样品的晶格常数略有减小,Ge掺杂后样品的载流子浓度较掺杂前低,迁移率增加;所有样品的Seebeck系数均为负值,且绝对值较未掺杂样品低,但Ge掺杂后样品的电导率提高了62%;x=0.5的样品在500 K附近取得最大ZT值1.25.
文摘本文采用Sn自熔剂法,制备Mg掺杂Sn基单晶笼合物Ba8Ga16-XMgXSn30(0 X 1.5),并对其结构及电传输性能进行研究.结果表明所制备化合物为具有空间群Iˉ43m的VIII型单晶笼合物,随Mg掺杂量的增加,对应化合物的熔点略有升高,晶格常数减小,掺杂样品中填充原子Ba的实际含量低于理想值8.0,其在十二面体空洞中的占有率约为0.93(Mg的名义含量X=1.5时).所有样品均表现为n型传导,Mg的掺入对材料的能带结构有一定影响,Mg掺杂后,样品的载流子浓度降低,Seebeck系数的绝对值、电阻率增加,Mg的名义含量X=1.5时,样品的功率因子在430 K附近取得最大值1.26×10-3W·m-1·K-2.
