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2 Archives of Materials Science and Engineering

2 2008

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Study of phase transition specific in polycrystalline Pb(Cd1/3Nb2/3)O3

Kajtoch C., Bąk W., Starzyk F., Gabryś M.

Archives of Materials Science and Engineering

2008

Vol. 29, nr 1

20-23

Purpose: of this paper was to isolate and attempt to identify experimentally specific features of paraelectric diffused phase of Pb(Cd1/3Nb2/3)O3 (PCN) not reported yet in the literature. Design/methodology/approach: we used was to measure and analyse the temperature and frequency dependence of polarization, energy loss, phase angle and ac-conductivity components. Findings: we have isolated four specific processes visible as specific behaviour of ĺ’(T, í); on ĺ” and phase angle also temperature and frequency dependences and three contributions to ac-conductivity. Practical implications: processes isolated will be used to construct a model of polarizability and energy loss as well as ac-conductivity in diffused paraelectric phase of PCN. Originality/value: of the paper rely on the possibility of experimental verification of temperature induced evolution of polar regions structure and dynamics created in high temperature region of paraelectric phase of PCN.

Elevated temperature induced dispersion phenomena in Ba1-xNaxTi1-xNbxO3

Bąk W., Starzyk F., Kajtoch C., Nogas-Ćwikiel E.

Archives of Materials Science and Engineering

2008

Vol. 29, nr 1

5-9

Purpose: of this paper was to investigate features of the dispersion of dielectric permittivity induced by elevated temperature (473K-723K) in polycrystalline solid solution of Ba1-xNaxTi1-xNbxO3 (for x=0.3 and x=0.4). Design/methodology/approach: used to perform this purpose was dielectric spectroscopy application to measure dielectric and electric parameters within the frequency range (20Hz-1MHz). Findings: Analysis of temperature and frequency dependences of real (ĺ’) and imaginary (ĺ”) parts of dielectric permittivity had pointed out on relaxor type of dielectric behaviour for both investigated samples in paraelectric phase. The thermal activation energy values of ac conductivity (for 100Hz) are similar to those of semiconductors. Values of ĺ’ for both materials (x=0.3, x=0.4) are consistent with literature quotations. Thus the polarisation behaviour of our materials seems to be similar to those described in the literature. Different behaviour of dielectric energy losses is postulated as originating from differences of samples microstructure. Research limitations/implications: Further investigations should be carried out in the range of low temperatures (down to 100K) and within a broaden frequency range (up to 1.8GHz) in order to establish the influence of chemical structure on ferroelectric-paraelectric phase transition. Originality/value: Dielectric properties for two new material prepared from nanopowders of BaTiO3 and NaNbO3 were described.