ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 42, (2) 41 - 48 (1998)


DIELECTRIC PROPERTIES AND CURIE-WEISS BEHAVIOUR OF Pb(Zn1/3Nb2/3)O₃-PbTiO₃-PbZrO₃ CERAMICS
 
Kovaľ Vladimír 1, Briančin Jaroslav 1, Alemany Carlos 2
 
1 Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 043 53 Košice, Slovak Republic
2 Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientfficas, Cantoblanco-280 49 Madrid, Spain

The effects of the sintering temperature and the Pb(Zn1/3Nb2/3)O₃ content on the dielectric and piezoelectric properties of xPb(Zn1/3Nb2/3)O₃- (l-x)Pb(Ti0.53Zr0.47)O1/3Nb2/3)O₃ ternary system were investigated. In the case of the PZN - PT ceramics with a low concentration of Zn1/3Nb2/3 (x = 0.05), the values of grain size (GS), Curie temperature (TC), mechnnical factor of quality (Qm), sintered density (ρ) and relative permittivity (εr) increase as well as maximum relative dielectic permittivity at TCmax), piezoelectric constants (d₃₃, d₃₁) and radial couplingfactor (kp) decrease with increasing sintering temperature (Ts). The relative dielectric permittivity rises sharply with increasing temperature to a high peak value, εr ≈ 42 000, at the phase tansition temperature, T, = 390"C. The introduction of a larger amount (x = 0.37) of Zn1/3Nb2/3 into the system resulted in the reduced permittivity (εmax ≈ 9000) at the phase transition (TC = 290 °C) and the broadening of the dielectric peak response. The transition temperatures are frequency dependent and shifted towards a higher temperature with increasing sintering temperatures. An extended Curie-Weiss law is observed for 0.37PZN - PZT ceramics. The coefficient of diffusivity, γ ≈ 1.6 - 1.9, and the relative volume fraction of micro polar regions calculated from Keizer physical model are discussed from the view-point of diffuse phase transition in disordered systems. The observed lowering of the spontaneous strain as the PZN content increased has been pronounced with increasing sintering temperature and lead to the increase of the room-temperature relative permittivity, εr ≈ 3200, and piezoelectric parameters d₃₃= 410 x 10⁻¹² C N⁻¹ and kp ≈ 49 %.


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