Synthesis and electrical resistivity analysis of ATO-coated talc

doi:10.1016/j.powtec.2012.02.039

Powder Technology

Volume 224, July 2012, Pages 124-128

https://doi.org/10.1016/j.powtec.2012.02.039 Get rights and content

Abstract

This paper provided an economical route to produce composite conductive powders. The aim of this work was to uniformly deposit antimony-doped tin oxide (ATO) nanoparticles onto talc matrix by co-precipitation to prepare Sb-SnO₂/talc (SST) composite conductive powders after calcination. The samples were characterized by X-ray diffraction and scanning electronic microscopy. In order to investigated the mechanism of hydrolysis reaction the precursors of ATO powder were researched by means of thermogravimetric analysis. Each effect of pH, coating ratio, SnCl₄·5H₂O/SbCl₃ mass ratio, hydrolysis temperature, calcination temperature and time on the resistivity of the SST powders was studied. Under the optimum experimental conditions, the resistivity of the composite conductive powders was less than 10 Ω cm.

Graphical abstract

The talc displayed the platelike structure and the surface was rather smooth. However, after coated with ATO the surface of talc was rough and a little out-of-flatness. It can be seen that the SST powders still retained the platelike structure after coated with ATO nanoparticles.

Highlights

► ATO was deposited on talc matrix to prepare composite conductive powders. ► The effect of all parameters on the resistivity of the SST powders was studied. ► Under the optimum conditions, the resistivity was less than 10 Ω·cm.

Introduction

Tin oxide (SnO₂) as a typical wide band gap n-type semiconductor (3.6 eV at 300 K) is widely applied in the fields of gas sensors [1], [2], optoelectronics [3], solar cells [4] and electrochromic devices [5]. However, due to its low intrinsic carrier density and mobility, the stoichiometric SnO₂ has low optical and electrical performance. Tin oxide doped with Sb, In, or F has been studied in the past to improve its optical properties and conductivity [6], [7], [8]. Among these materials, the antimony-doped tin oxide (ATO) is considered as a low-cost possible alternative to rather expensive indium tin oxide (ITO) because of its mechanically hard and electronically stable material in oxidizing environment [9]. The ATO is well-known for its applications in solar cell and heat-reflecting coating [10], [11].

As well known the traditional conductive powders include metal, carbon black, carbon fiber, metal fiber and metal oxides [12]. The price of metal powders such as gold powders mainly used in the places where require strict conductivity or electromagnetic shielding is too high, while the copper, nickel or aluminum are easily oxidized and lead to reduce conductivity. Carbon black is mostly used but it is limited in light color materials, and makes the products embrittlement. The metal fiber is hard to disperse, and carbon fiber's price is expensive too. However the transparent conductive oxides (TCOs) like ITO, ATO, and Al-doped ZnO (AZO) have received great attention for their excellent properties in the solid-state chemical and physical communities [13]. Furthermore to reduce the cost, composite conductive powders have been researched and some of them have been synthesized using some cheap minerals. Yang and his group have studied the coating of ATO nanoparticles on kaolinite particles [12]. Under the optimum experimental conditions, they found that the resistivity was less than 10 Ω cm. They also produced ATO nanoparticles deposited on barite [14]. Sladkevich et al. synthesized ATO-coated six different crystalline and amorphous materials from H₂O₂ solutions, which is a new generic film coating from basic solutions [15]. The influence of iron present in clays in the adsorption of pyrrole and possible in situ formation of polypyrrole (PPy) has been studied by Letaïef et al. [16]. The deposition of ATO coatings has been reported by many methods, such as chemical vapor deposition [17], thermal evaporation [18], sol–gel dip coating [19], and MOCVD [20].

In this paper, the antimony-doped tin oxide (ATO) nanoparticles from the reaction of SnCl₄·5H₂O and SbCl₃ acidic solutions and NaOH were deposited onto the talc matrix. Subsequent calcination formed crystalline Sb–SnO₂/talc SST composites. Talc shows smooth texture, appropriate hardness, good flexibility, forming effect well and it also can reduce the cost of the raw materials. In this work, the effects of different experimental parameters, including pH, coating ratio, SnCl₄·5H₂O/SbCl₃ mass ratio, hydrolysis temperature, calcination temperature and time, on the resistivity were investigated.

Section snippets

Materials

The talc used as substrate was obtained from Yingkou Sea Talc Mining Co., Ltd. It showed plate-like morphology and its particle size was from 1 μm to 10 μm, which was examined by scanning electron microscopy (SEM, S-4700 field emission, Hitachi, Ltd). The tin (IV) chloride pentahydrate (SnCl₄·5H₂O), antimony (III) chloride (SbCl₃), hydrochloric acid and sodium hydroxide used in this experiment were purchased from Sinopharm Chemical Reagent Co., Ltd, and were of analytical grade and without

Morphology of ATO on the surface of talc particles

Fig. 1 shows the SEM images of the talc and 50% coating ratio, 10% SnCl₄·5H₂O/SbCl₃ mass ratio SST powders prepared under pH 2.5, hydrolysis at 40 °C and calcinated at 700 °C for 2 h. The talc displayed the plate-like structure and the surface was rather smooth. However, after coated with ATO the surface of talc was rough and a little out-of-flatness. The size of the ATO particle was approximate from 20 nm to 40 nm (Fig. 1c) and there were some agglomerations between particles, which increased the

Conclusions

Composite conductive powders with ATO nanoparticles coated on talc powders were synthesized by co-precipitation method. Effects of different parameters such as pH, coating ratio, SnCl₄·5H₂O/SbCl₃ mass ratio, hydrolysis temperature, calcination temperature and time on the resistivity of the SST powders were studied under the optimum experimental conditions, the lowest resistivity was 8.9 Ω cm. The SST powder can be prepared at a hydrolysis temperature 40 °C, pH of 1.5–2.5, SbCl₃ to SnCl₄ with mass

Acknowledgment

This work was supported by the National Natural Science Foundation of China (NSFC, nos. 20876100 and 20736004), the National Basic Research Program of China (973 Program, no. 2009CB219904), the Commission of Science and Technology of Suzhou Municipality (nos. YJS0917, SG0978), the Technology Innovation Foundation of Suzhou SND District, SIP District and MOST (11C26223204581), the Natural Science Foundation of Jiangsu Prov. (BK2011328) and the Minjiang Scholarship of Fujian Province.

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The changing trend also showed a U-shaped curve that first decreased to the lowest value at 1.5 h, and then increased. In the preparation process, the surfaces of CMs were coated with antimony-doped tin hydroxide colloid, and then calcined to form an oxide coating layer [39]. Therefore, the calcination time had a great influence on the volume resistivity of ATCM.
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The main reasons are the high cost and the gray color resulting in an undesirable appearance to the final product. Due to the high price of ATO materials, antistatic composite powders have been researched and some of them have been synthesized using cheap minerals as the substrate, such as kaolinite [8], barite [9], talc etc. [10]. These antistatic composite materials have a greater potential prospect than traditional materials including metal [11], carbon black [12], metal fiber [13] and metal oxides [14].
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View full text

Synthesis and electrical resistivity analysis of ATO-coated talc

Abstract

Graphical abstract

Highlights

Introduction

Section snippets

Materials

Morphology of ATO on the surface of talc particles

Conclusions

Acknowledgment

Solar Energy Materials

Materials Letters

Solar Energy Materials and Solar Cells

Materials Research Bulletin

Journal of Alloys and Compounds

Applied Clay Science

Thin Solid Films

Thin Solid Films

Materials Letters

Applied Surface Science

Angewandte Chemie International Edition

Nature