Article

Applied Physics A

, Volume 91, Issue 1, pp 167-171

First online:

Phase transition and electrical properties of (K0.5Na0.5)(Nb1-xTax)O3 lead-free piezoelectric ceramics

  • Dunmin LinAffiliated withDepartment of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic UniversityCollege of Chemistry and Materials Science, Sichuan Normal University Email author 
  • , K.W. KwokAffiliated withDepartment of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University
  • , H.L.W. ChanAffiliated withDepartment of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University

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Abstract

(K0.5Na0.5)(Nb1-xTax)O3 lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique. The results of X-ray diffraction reveal that Ta5+ diffuses into the K0.5Na0.5NbO3 lattices to form a solid solution with an orthorhombic perovskite structure. Because of the high melting temperature of KTaO3, the (K0.5Na0.5)(Nb1-xTax)O3 ceramics can be sintered at higher temperatures. The partial substitution of Ta5+ for the B-site ion Nb5+ decreases both paraelectric/cubic–ferroelectric/tetragonal and ferroelectric/tetragonal–ferroelectric/orthorhombic phase transition temperatures, TC and TO-T. It also induces a relaxor phase transition and weakens the ferroelectricity of the ceramics. The ceramics become ‘softened’, leading to improvements in d33, kp, kt and εr and a decease in Ec, Qm and Np. The ceramics with x=0.075–0.15 become optimum, having d33=127–151 pC/N, kp=0.43–0.44, kt=0.43–0.44, εr=541–712, tanδ=1.75–2.48% and TC=378–329 °C.