Preparation and Property of La1-xNdxB6 Cathode Material

doi:10.15541/jim20140471

Abstract

Abstract:

High purity and high density La_1-_xNd_xB₆ bulks were prepared by using evaporation condensation combined spark plasma sintering (SPS) with high-purity metal La, Nd bulks and B powder as raw materials. Phase component, the mechanical properties, the resistivity and the thermionic emission properties of La_1-_xNd_xB₆ bulks were investigated systematically. The results show that high purity and high density La_1-_xNd_xB₆ single-phase bulk material can be prepared by using the above mentioned technology. The sintered samples show high value of Vickers hardness (26.70 GPa) and bending strength (230.48 MPa). According to the thermionic emission results, the bulk of La_0.1Nd_0.9B₆materials exhibits optimum thermal emission properties, the emission current density is 32.04 A/cm² and zero field current density reaches 12.72 A/cm² at the temperature of 1600℃ and the applied voltage of 4 kV, which is better than LaB₆ and NdB₆ bulk samples under the same conditions. It is shown that proper Nd content is benefit to reducing the work function and improving the thermionic emission properties, the average of effective work function for La_0.1Nd_0.9B₆ at different temperatures is 2.72 eV.

Key words: rare-earth hexaborides, evaporation-condensation, spark plasma sintering, thermionic emission property

CLC Number:

TQ174

LIANG Chao-Long, ZHANG Xin, ZHANG Jiu-Xing, ZHANG Fan-Xing, WANG Yang. Preparation and Property of La_1-_xNd_xB₆ Cathode Material[J]. Journal of Inorganic Materials, 2015, 30(4): 363-368.

Figures/Tables 8

Fig. 1 TEM and SEM images of powders TEM images of LaH2 (a) and NdH2 (b) nanopowders; SEM image of B powders (c)

Fig. 2 XRD patterns of La1-xNdxB6 polycrystalline prepared by in situ reaction

Table 1 Relative density and lattice constant of La1-xNdxB6 polycrystalline

Sample	Lattice constant /nm	Theory density /(g·cm^-3)	Actual density /(g·cm^-3)	Relative density/%
LaB₆	0.4151	4.712	4.534	96.2
La_0.9Nd_0.1B₆	0.4144	4.734	4.545	96.0
La_0.7Nd_0.3B₆	0.4135	4.782	4.564	95.4
La_0.5Nd_0.5B₆	0.4122	4.830	4.665	96.6
La_0.3Nd_0.7B₆	0.4123	4.878	4.575	93.8
La_0.1Nd_0.9B₆	0.4121	4.926	4.635	94.1
NdB₆	0.4120	4.936	4.752	96.3

Fig. 3 Fracture SEM images of La1-xNdxB6 polycrystalline (a) x=0.1; (b) x=0.3; (c) x=0.5; (d) x=0.7; (e) x=0.9

Fig. 4 Vickers hardness and bending strength curves of La1-xNdxB6 as a function of Nd content

Fig. 5 Electrical resistivity curves of La1-xNdxB6 as a function of testing temperature

Table 2 Effective work function of La1-xNdxB6 at different testing temperatures

Nd content , x	j₀/ (A?cm^-2)			Average work function /eV
Nd content , x	1400℃	1500℃	1600℃	Average work function /eV
x=0	-	5.10	12.42	2.78
x=0.1	-	-	2.29	3.07
x=0.3	-	1.11	4.36	2.93
x=0.5	-	11.02	19.13	2.70
x=0.7	-	2.50	4.01	2.93
x=0.9	2.29	10.12	12.72	2.72
x=1.0	4.42	7.54	9.25	2.72

Fig. 6 Calculate J0 of La1-xNdxB6 polycrystalline by method of Schottky line (a) x=0.1; (b) x=0.3; (c) x=0.5; (d) x=0.7; (e) x=0.9; (f) x=0; (g) x=1.0

References 13

[1]	TANAKA T, NISHITANI R, OSHIMA C, et al.The preparation and properties of CeB6, SmB6, and GdB6.J. Appl. Phys., 1980, 51(7): 3877-3880.
[2]	CHEN CHUN-HUA, AIZAWA T, IYI N, et al.Structural refinement and thermal expansion of hexaborides.Journal of Alloys and Compounds, 2004, 366(1/2): L6-L8.
[3]	LATE D J, SINGH V R, SINHA S, et al.Synthesis of LaB6 micro/nano structures using picoseconds (Nd: YAG) laser and its field emission investigations. Appl. Phys. A, 2009, 97(4): 905-909.
[4]	ZHOU SHEN-LIN, LIU DAN-MIN, ZHANG JIU-XING.Fabrication and characterization of high-purity nanostructured bulk LaB6 polycrystal cathode material.Journal of Inorganic Materials, 2008, 23(6): 1199-1204.
[5]	ZHOU SHEN-LIN, ZHANG JIU-XING, LIU DAN-MIN, et al.Properties of CeB6 cathode fabricated by spark plasma reactive liquid Phase Sintering Method.Journal of Inorganic Materials, 2009, 24(4): 793-797.
[6]	SCHMIDT P H, JOY D C.Low work function electron emitter hexaborides. J. Vac. Sci. Technol., 1978, 15(6): 1809-1810.
[7]	BAO LI-HONG, TEGUS O, ZHANG JIU-XING, et al.Large emission current density of LaxCe1-xB6 high quality single crystals grown by floating zone technique.Journal of Alloys and Compounds, 2013, 558(13): 39-43.
[8]	HUANG MEI-SONG, CHEN YUN-ZHI, ZHANG YAO-BIN, et al. Preparation of high-density LaB6 polycrystal.Rare Metals andCemented Carbides, 2012, 40(3): 33-38.
[9]	CHENG WEI, HUANG MEI-SONG, YANG LU-HUI, et al.Preparation of high-density LaB6 polycrystalline by low-pressure solid-state sintering.Mining AND Metallurgical Engineering, 2014, 34(2): 122-124.
[10]	MA RU-GUANG, LIU DAN-MIN, ZHOU SHEN-LIN, et al.Fabrication and emission property of polycrystalline La0.4Pr0.6B6 bulk prepared by spark plasma sintering.Journal of Inorganic Materials, 2010, 25(7): 743-747.
[11]	BAO LI-HONG, ZHANG JIU-XING, ZHOU SHEN-LIN.Effect of Ba-doping on the structural, grain orientation and thermionic emission properties of hexaboride GdB6.Journal of Inorganic Materials, 2011, 26(10): 1116-1120.
[12]	CHEN CH, XUAN Y, OTANI S, et al.Temperature and loading time dependence of hardness of LaB6, YB6 and TiC single crystals.Journal of Alloys and Compounds, 2003, 350(1/2): L4-L6.
[13]	ZHOU SHEN-LIN, ZHANG JIU-XING, LIU DAN-MIN.Properties of high density LaB6 cathode prepared by spark plasma solid phase sintering.High Power Laser and Particle Beams, 2010, 22(1): 171-175.

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Preparation and Property of La_1-_xNd_xB₆ Cathode Material

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