Effect of Firing Conditions on Phase Formation, Microstructure, and Electrical Properties of (K 0.5 Na 0.5 )(Nb 0.7 Ta 0
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https://doi.org/10.1007/s11664-020-08374-6 2020 The Minerals, Metals & Materials Society
Effect of Firing Conditions on Phase Formation, Microstructure, and Electrical Properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 Ceramics Synthesized by Solid-State Combustion Method SURIRAT YOTTHUAN,1 THITIRAT CHAROONSUK,2 NARATIP VITTAYAKORN,3 SARAWUT THOUNTOM,1,4 TAWAT SURIWONG,4,5 THANYA UDEYE,1 and THEERACHAI BONGKARN 1,4,6 1.—Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand. 2.—Department of Materials Science, Faculty of Science, Srinakharinwirot University, 114 Sukhumvit 23, Watthana, Bangkok 10110, Thailand. 3.—Advanced Materials Research Unit, Faculty of Science, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand. 4.—Research Center for Academic Excellence in Applied Physics, Faculty of Science, Narasuan University, Phitsanulok 65000, Thailand. 5.—School of Renewable Energy Technology, Naresuan University, Phitsanulok 65000, Thailand. 6.—e-mail: [email protected]
The effect of the firing conditions on the phase formation, microstructure, and electrical properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 (KNNT) ceramics synthesized by the solid-state combustion technique using glycine as fuel has been investigated. All samples were calcined at 600C to 800C for 2 h and sintered at 1150C to 1190C for 2 h to 5 h. Pure KNNT powders were produced after calcination at 600C for 2 h. The average particle size increased when the calcination temperature was increased. The KNNT powder calcined at 600C for 2 h showed rather square morphology with average particle size of 160 nm. The x-ray diffraction (XRD) analysis results for the ceramics revealed the presence of orthorhombic (O) and tetragonal (T) phases in all samples. When sintering at 1150C for 4 h, the O:T ratio was 50:50, as verified by the Rietveld refinement technique. The average grain size, density values, and dielectric properties tended to increase when the dwell time was increased from 2 h to 4 h, but then degraded. The KNNT ceramic produced at the optimum firing condition (1150C for 4 h) showed good crystalline morphology, the highest density (q = 5.28 g/cm3), the highest dielectric constant (eC = 5002), and good ferroelectric behavior (Pr = 18.50 lC/cm2 and Ec = 9.04 kV/cm). Key words: KNNT, firing conditions, solid-state combustion method, rietveld refinement, dielectric properties
INTRODUCTION Since the 1950s, lead zirconate titanate (PZT)based ceramics (PbZr1xTixO3) have received much attention because of their excellent piezoelectric
(Received December 2, 2019; accepted July 29, 2020)
coefficient (d33 200 pC/N to 750 pC/N) and high Curie temperature (TC 180C to 320C), finding applications in various electronic devices (e.g., sensors, actuators, ultrasound transducers, etc.).1–4 However, drawbacks of PZT-based ceramics include that PbO and Pb3O4 are released during their manufacturing process at high temperatures and that disposal of such electronic devices causes leaching of Pb into the env
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