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Mohamed Elaatmani, A. Zegzouti, Francesco Capitelli, Anna Grazia Giuseppina Moliterni, A. Migliori, G. Calestani

Synthesis, X-ray crystal structure and dielectric measurementsof a tetragonal tungsten bronze: Pb_0.75K_1.80Li_1.70Nb₅O₁₅

Typical crystals Pb_0.75K_1.80Li_1.70Nb₅O₁₅, belonging to tetragonal tungsten bronze materials, were grown by the slow cooling technique. The crystals were characterized at room temperature by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HREM). The structure, solved combining information obtained by HRTEM images and Direct Methods application to single crystal XRD data, was refined by full-matrix least-squares technique in the P4bm space group to a final R = 0.031. The lattice constants are a = 12.540(2), c = 4.037(1) Å, V = 634.8(2) ų, at 293 K. There are two formulas per unit cell, for a calculated density of 4.928 Mg/m³. Dielectric measurements, carried out along the [001] direction in the frequency 10³ Hz, showed the existence of the paraelectric-ferroelectric transition at 628 K and of a further maximum of ε′_r (with a very weak intensity) at T₁ = 150 K.

Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0044-2968
Volume: 218, 01/2003
Pages: 026

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