A series of La0.67Ca0.33-0.5xLixMnO3 ceramic (x=0.00, 0.05, 0.10, 0.15, 0.20) were prepared by sol-gel technique. The crystal structures were analyzed by X-ray diffraction (XRD), the surface morphology and grain boundaries were investigated by scanning electron microscope (SEM), and the temperature dependence of the resistivity (R-T) of the bulk samples were studied by the standard four-probe method. It can be indexed with an orthorhombic structure for all of La0.67Ca0.33-0.5xLixMnO3 polycrystalline ceramics. The results showed that with the increase of the content of Li element, the unit cell volume decrease and the resistance increases. The insulator-metal transition temperature TP shifts to lower temperature and the temperature coefficient of resistivity (TCR) decrease continually. The data of resistivity on low-temperature (TP) have been fitted with the relation ρ(T)=ρ0+ρ2T2+ρ4.5T4.5, the high-temperature (T>TP) resistivity data were explained using small-polaron hopping (SPH) and variable-range hopping (VRH) models. The resistivity data in whole temperature range (100—300 K) can be fitted by percolation model. Polaron activation energy Ea is found to increases with increasing the contant of Li (x), which suggests that Li doping decrease bond angle of Mn 3+-O 2--Mn 4+, thereby the increase of effective band gap and the decrease of double exchange coupling, this is the reason of the increase of resistivity.
1 Gennes P G D. Effect of double exchange in magnetic crystals[J]. Physical Review, 1960,118(1):141.
2
Attfield J P . ‘A’ cation control of perovskite properties[J]. Crystal Engineering, 2002,5(3-4):427.
3
Woodward P M, Vogt T, Cox D E , et al. Influence of cation size on the structural features of Ln1/2 A1/2MnO3 perovskites at room temperature[J]. Chemistry of Materials, 1998,10(11):3652.
4
Wang Z M, Ni G, Sang H , et al. The effect of average A-site cation radius on TC in perovskite manganites[J]. Journal of Magnetism and Magnetic Materials, 2001,234(2):213.
5
Kuberkar D G , et al. Grain morphology and size disorder effect on the transport and magnetotransport in sol-gel grown nanostructured manganites[J]. Applied Surface Science, 2012,285(22):9041.
6
Luo Junmei, Zhang Hui, Cui Qi , et al. Studies on (La0.67Ca0.33-MnO3)1-x∶Agx polycrystalline ceramics with high temperature coefficients of resistance[J]. Journal of Synthetic Crystal, 2015,44(8):2178(in Chinese).
Fan J, Xu L, Zhang W , et al. Effect of A-site average radius and cation disorder on magnetism and electronic properties in manganite La0.6 A0.1Sr0.3MnO3(A=Sm, Dy, Er)[J]. Journal of Materials Science, 2015,50(5):2130.
9
Mnefgui S , et al. Electrical transport properties and transport-entropy correlations in La0.57Nd0.1Sr0.33MnO3 manganite[J]. Journal of Magnetism and Magnetic Materials, 2015,384(15):219.
10
Nakajima T, Ueda Y . Structures and electromagnetic properties of the A-site disordered Ba-based manganites R0.5Ba0.5MnO3 (R=Y and rare earth elements)[J]. Journal of Alloys and Compounds, 2014,383(1-2):135.
11
Kansara S B, Dhruv D, Joshi Z , et al. Structure and microstructure dependent transport and magnetic properties of sol-gel grown nanostructured La0.6Nd0.1Sr0.3MnO3 manganites: Role of oxygen[J]. Applied Surface Science, 2015,356(30):1272.
12
11 Voorhoeve R J H, Remeika J P, Trimble L E , et al. Perovskite-like La1-xKxMnO3 and related compounds: Solid state chemistry and the catalysis of the reduction of NO by CO and H2[J]. Journal of Solid State Chemistry, 1975,14(4):395.
13
Ahmed S A . Structural and electrical properties in La1-xLixMnO3[J]. Journal of Magnetism and Magnetic Materials, 2013,340:131.
14
Gao Xiang, Ma Ji, Zhang Hui . Structure and electrical properties of La0.75Ca0.25MnO3 polycrystalline ceramic and thin films[J]. Rare Metal Materials and Engineering, 2014,43(10):2415(in Chinese).
Yanapu K L, Samatham S S, Kumar D , et al. Effect of bismuth doping on the physical properties of La-Li-Mn-O manganite[J]. Applied Physics A, 2016,122(3):199.
17
Manjunatha S O, Rao A, Lin T Y , et al. Effect of Ba substitution on structural, electrical and thermal properties of La0.65Ca0.35-x-BaxMnO3 (x=0, 0.25) manganites[J]. Journal of Alloys and Compounds, 2015,619:303.
18
Hcini S, Khadhraoui S, Zemni S , et al. Percolation model of the temperature dependence of resistivity in Pr0.67A0.33MnO3 (A= Ba or Sr) manganites[J]. Journal of Superconductivity and Novel Magne-tism, 2013,26(6):2181.
19
Navasery M, Halim S A, Dehzangi A , et al. Electrical properties and conduction mechanisms in La2/3Ca1/3MnO3 thin films prepared by pulsed laser deposition on different substrates[J]. Applied Phy-sics A, 2014,116(4):1661.
20
Shiffer P, Ramirez A P, Bao W , et al. Low temperature magnetoresistance and the magnetic phase diagram of La1-xCaxMnO3[J]. Physical Review Letters, 1995,75(18):3336.
21
Vlakhov E S, Chakalov R A, Chakalov R I , et al. Influence of the substrate on growth and magnetoresistance of La0.7Ca0.3MnO3 thin films deposited by magnetron sputtering[J]. Journal of Applied Physics, 1998,83(4):2512.
22
Hcini S, Zemni S, Triki A , et al. Size mismatch, grain boundary and bandwidth effects on structural, magnetic and electrical properties of Pr0.67Ba0.33MnO3 and Pr0.67Sr0.33MnO3 perovskites[J]. Journal of Alloys and Compounds, 2011,509(5):2181.
23
Holstein T . Studies of polaron motion: Part Ⅱ. The “small” pola-ron[J]. Annals of Physics, 1959,8(3):343.
24
Lakshmi Y K, Reddy P V . Influence of sintering temperature and oxygen stoichiometry on electrical transport properties of La0.67-Na0.33MnO3 manganite[J]. Journal of Alloys and Compounds, 2009,470(1-2):67.
25
Millis A J, Shraiman B I, Mueller R . Dynamic Jahn-Teller effect and colossal magnetoresistance in La1-xSrxMnO3[J]. Physical Review Letters, 1996,75(1):175.
26
4 Mott N F, Davis E A . Electronic processes in non-crystalline mate-rials[J].Oxford University Press, 1979,25(12):55.
27
5 Banerjee A, Pal S, Chaudhuri B K . Nature of small-polaron hopping conduction and the effect of Cr doping on the transport properties of rare-earth manganite La0.5Pb0.5Mn1-xCrxO3[J]. Journal of Chemical Physics, 2011,115(3):1550.
28
6 Manjunatha S O, Rao A, Awana V P S , et al. Investigation on magnetic, electrical and thermoelectric power of Bi-substituted La0.8-Ca0.2MnO3 manganites[J]. Journal of Magnetism and Magnetic Materials, 2015,394:130.
29
7 Oumezzine M, Kallel S, Pena O , et al. Correlation between structural, magnetic and electrical transport properties of barium vacancies in the La0.67Ba0.33-xMnO3 (x=0, 0.05, and 0.1) manganite[J]. Journal of Alloys and Compounds, 2014,582(3):640.