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利用高压合成方法,在压力为2 GPa、温度为900 K的条件下,以NaN3作为添加剂,成功地合成出了Na填充型的方钴矿化合物CoSb3。X射线衍射(XRD)研究结果表明,当Na填充量达80%时,合成的Na填充型方钴矿化合物CoSb3仍为单相方钴矿结构,没有Na和NaN3等杂质峰。在室温下对不同Na填充量的样品进行了电阻率(ρ)和Seebeck系数(α)的测试,研究了不同Na填充量对样品电阻率、Seebeck系数和功率因子(α2σ)的影响。研究结果表明:室温下,样品的电导率随Na填充量的增加而增大,Seebeck系数的绝对值随Na填充量的增加而减小。当Na填充量为0.4时,样品获得了最高的功率因子(8.72 μW·cm-1·K-2),此值高于He等报道的利用热压法制备的CoSb3的值。填充量对样品电输运特性的影响规律与Pei等研究的K填充型CoSb3的研究结果相一致。上述研究结果表明,高压合成技术有利于提高填充型方钴矿化合物的填充量,并有效地提高样品的电输运特性。 相似文献
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利用溶胶-凝胶法制备出了纳米晶ZnO与含有3%摩尔分数SnO2的ZnO/SnO2复合材料,在六面顶压机上对制备出的两种样品进行了室温下、6GPa的高压处理。采用X射线衍射(XRD)、透射电子显微镜(TEM)和光致荧光谱(PL)等方法,对高压处理前后样品的结构和发光性质进行了表征。结果表明:高压处理后回收到的纳米晶ZnO和ZnO/SnO2复合材料的平均粒径分别减小5.9%和26.3%;高压处理后ZnO和ZnO/SnO2复合材料光致发光谱的发光带强度都有所降低,但ZnO/SnO2复合材料发光带强度降低幅度比纯ZnO小,对产生这些现象的原因进行了讨论。 相似文献
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高压能增加陶瓷烧结的致密驱动力和抑制陶瓷晶粒的长大。用高压辅助烧结的方法得到了晶粒尺寸约为60和30 nm的致密纳米BaTiO3陶瓷。BaTiO3陶瓷的晶体结构随温度的变化由变温Raman光谱来研究。在温度范围-190℃到200℃内,与粗晶的BaTiO3陶瓷相比,纳米BaTiO3陶瓷Raman散射结果表明,随着晶粒尺寸的减小,Raman峰的强度变弱,相变越来越弥散,出现了相变峰的消失;而且随着温度的升高,在纳米BaTiO3陶瓷甚至在30 nm BaTiO3陶瓷中都有与粗晶相同的从三方相到正交相到四方相到立方相的连续相变。变温Raman散射也表明,当晶粒大小减小到纳米尺寸时,纳米BaTiO3陶瓷表现出与粗晶不同的新颖性质。在一定的温度范围内,存在多种铁电相的共存。 相似文献
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Ferroelectric behaviour of 30nm BaTiO3 ceramics prepared by high pressure assisted sintering 下载免费PDF全文
Dense nanocrystalline BaTiO3 ceramics with a homogeneous grain size of 30 nm was obtained by pressure assisted sintering. The ferroelectric behaviour of the ceramics was characterized by the dielectric peak at around 120 ℃, the P-E hysteresis loop and some ferroelectric domains. These experimental results indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm. The ferroelectric property decreasing with decreasing grain size can be explained by the lowered tetragonality and the 'dilution' effect of grain boundaries. 相似文献
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Effect of Annealing on Ferroelectric Properties of Nanometre BaTiO3 Ceramics Prepared by High Pressure Sintering Method 下载免费PDF全文
Dense nanocrystalline BaTiO3 ceramics with a grain size of 5Onto are prepared under 6 GPa at 1273K using a high pressure sintering method. The sintered bulk is uniform and the relative density is above 97%. We anneal the ceramic samples in oxygen with various temperatures and for the annealing, several broadened peaks can be observed at different times without apparent grain growth. After about 378K( by dielectric measurements. However, these peaks are very different from those of coarser-grained ceramics. It is indicated that both the elimination of oxygen vacancies and the release of residual stresses caused by high pressure greatly improve the overall ferroelectric properties of BaTiO3 ceramics. The observation of nearly linear polarization hysteresis loop after anneal provides the solid evidence of ferroelectricity in these nano-sized BaTiO3 ceramics. It is believed that the absence of 90° domains and the existence of poor-permittivity nonferroelectric grain boundaries contribute to the slim loop. 相似文献
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从理论上讨论了一阶和二阶斯托克斯与反斯托克斯拉曼散射截面的温度依赖关系;在293K至401K的温度范围内,测量了BaTiO3单晶斯托克斯和反斯托克斯过程的偏振拉曼光谱;通过对BaTiO3单晶斯托克斯和反斯托克斯拉曼光谱的综合分析,证实在X(ZZ)Y几何配置下测量到的位于275和514cm-1处的强峰为一阶拉曼光谱。此结果支持了BaTiO3铁电相变机制的有序—无序模型。 相似文献
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H. R. Zeng F. Sun K. Y. Zhao F. X. Li X. W. Zhang R. Q. Chu H. S. Luo G. R. Li 《固体物理学:研究快报》2013,7(9):672-675
The domain configurations and local piezoresponse property of the [720]‐cut BaTiO3 single crystal and [001]‐oriented BaTiO3 crystal were investigated by high‐resolution piezoresponse force microscopy. Large differences in their surface topography features, domain configurations and local piezoresponse were found between [720]‐cut and [001]‐oriented BaTiO3 crystals. The large surface bending angle due to ferroelastic domain walls leads to a high strain energy appearing in the [720]‐cut BaTiO3, further resulting in unique band‐like topographic features, needle domains for stress compensation and locally ultrahigh piezoelectric response as well. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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采用高压烧结技术制备了按偏离化学计量比配制的PbTe基热电材料(Pb0.55Te0.45),重点研究了烧结压力对材料热电性能的影响。研究结果表明:高压烧结过程能有效降低材料中的晶格缺陷,从而显著改变样品中的载流子浓度及其迁移率。与未经烧结的常压熔融样品相比,高压烧结样品的Seebeck系数得到大幅提高,电导率略有降低,室温热导率降低了50%,所以高压烧结样品的品质因子得到较大提高。当烧结压力为2 GPa时,所得样品在700 K时其品质因子达到0.59,相比未经烧结的常压熔融样品提高了150%。 相似文献
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采用X射线衍射(XRD)分析、扫描电子显微镜(SEM)和能谱分析(EDX)等方法,对在压力5.6 GPa、温度1 460 ℃条件下,加热时间分别为2、3、4、6、8、10 min的聚晶金刚石复合片(PDC)样品进行了分析。结果表明:PDC的烧结经历了金刚石的石墨化过程,而且在烧结过程中金刚石层表面的XRD图谱出现了WC衍射峰,强度由弱到强,再由强到弱,直至消失;进一步的研究发现,PDC中助烧结剂Co的晶格常数因C和W原子的固溶会变大,并随PDC加热时间的延长出现一个峰值;从硬质合金基体扩散到金刚石层的Co由于扩散通道各异、所受阻力不同,使得其分布不均匀。 相似文献
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K. Y. Zhao H. R. Zeng X. W. Zhang K. Q. Xu H. Z. Yu G. R. Li H. S. Luo 《固体物理学:研究快报》2014,8(3):279-282
The 3ω ‐scanning thermal microscopy and piezoresponse force microscopy techniques were combined to characterize the local thermal conductivity (λ) of ferroelastic domains in [720]‐oriented and [001]‐oriented BaTiO3 single crystal. The [720]‐oriented BaTiO3 showed a local λ value of 3.39 W/m·K, while it was 5.95 W/m·K for [001]‐oriented BaTiO3. The underlying mechanism for such drastic thermal conductivity reduction in [720]‐oriented BaTiO3 is ascribed to a stronger phonon‐scattering effect due to the high strains appearing in [720]‐oriented BaTiO3 single crystals. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献