The Synthesis and Structure of New Perovskite-type Niobate Processed in Millimeter Wave Field
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The Synthesis and Structure of New Perovskite-type Niobate Processed in Millimeter Wave Field Hanxing Liu, Long Zou, Jian Zhou, Guangjiang Yuan1, Hua Hua, Dabing Luo, Jirun Luo1, Shixi Ouyang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Wuhan 430070, P.R. China 1 The Institute of Electronics, Chinese Academy of Sciences, Beijing, 100080, P. R. China ABSTRACT In present paper a new niobate materials Ba5LixTixNb10-xO30 were synthesized by doping Li+ in the system BaO- TiO2- Nb2O5 in millimeter wave field. X-ray diffraction (XRD) quantitative and scanning transition spectroscopy (SEM) analysis were employed to study crystal structure and microstructure of reaction products. It was found that pure products could be obtained at temperature 900℃, 8 min which is lower comparing with that by conventional method. The XRD data shown the crystal belongs to tetragonal tungsten bronze structure with space group P4bm. The grain size synthesized in millimeter wave field had smaller size, narrower distribution, better sinter-ability, and without hard agglomeration comparing whit that obtaining from conventional synthesis. At lower temperature Ba5LiTiNb9O30 is a tetragonal ferroelectric phase. INTRODUCTION Ba5LixTixNb10-xO30 is a kind of perovskite-type materials, which is used as candidate of ferroelectric material which is usually synthesized through solid-state reaction [1]. The use of microwaves for heating, sintering/densification, and annealing of ceramic powders and compacts is becoming a well-researched area that is due to its advantages include the ability to deposit energy volumetrically in the sample and the possibility of rapid heating and cooling profiles. Most research on ceramic processing by microwaves to date is based on 2.45 GHz microwave applicators [2-5]. However, such applicators do not couple microwave power efficiently to low-loss ceramics and have heating gradients. A number of low- and high-frequency microwave sintering studies have been reported [6-16], and the results have generally indicated that sintering proceeds much faster in microwave furnaces. Lower sintering temperatures are desirable for minimizing grain growth in fine and ultrafine-grained ceramics. In the present study, we synthesize Ba5LiTiNb9O30 in millimeter wave field. XRD and SEM were employed to detect microstructure of the reaction products. The ferroelectric properties of the compound were studied. EXPERIMENTAL METHODS 34.5GHz pulsed Gyrotron system for ceramic sintering The diagram of the 34.5GHz pulsed gyrotron system for the materials synthesis was presented in fig.1. The main parts include gyrotron oscillator, directional coupler, rotating mode filter, sintering furnace, and control circuits. The gyrotron operates in the TE30 circular waveguide mode at voltage of 42kV and currents up to 12A. The gyrotron currently deliver 60kW peak power to the applicator at 4%~5% duty factor for ceramic sintering.
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Gyrotron Oscillator
Direct
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