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Analysis of small samples of lanthanum-doped lead zirconate titanate (PLZT) by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) is presented. The powdered material in ca. 30 mg was suspended in water and collected on the membrane filter. The pure oxide standards (PbO, La2O3, ZrO2 and TiO2) were used for calibration. The matrix effects were corrected using a theoretical influence coefficients algorithm for intermediate-thickness specimens. The results from XRF method were compared with the results from the inductively coupled plasma optical emission spectrometry (ICP-OES). Agreement between XRF and ICP-OES analysis was satisfactory and indicates the usefulness of XRF method for stoichiometry determination of PLZT.

Auxetic structures exhibit unusual changes in size, expanding laterally upon stretching instead of contracting. This paper presents this effect in a failsafe mode in structures made of rigid squares. We applied the concept of auxetic structures made of rigid rotating squares (from Grima and Evans) and offer a novel solution for connecting them. By introducing axes of rotation on the surface of the squares, a reliable working system is obtained, free from stress, in which the squares can come into contact with each other and completely cover the surface of the structure, or, in the open position, form regularly arranged pores. Herein, we present a new 2D auxetic metamaterial that is mathematically generated based on a theoretical relationship of the angle between the edges of a square and the position of the axis of rotation. Physical models were generated in the form of a planar structure and in the form of a circular closed structure. Such physical models confirmed our initial considerations and the geometrical relationships, offering new application possibilities. The novel structure that was designed and manufactured for the purpose of the paper can be considered as a new proposal in the market of auxetic materials.

The near-infrared luminescence properties of Pr 3+ /Yb 3+ :PLZT ferroelectric ceramics have been examined for the first time. Independently, upon either 450 nm (Pr 3+ ) or 980 nm (Yb 3+ ) excitation, luminescence centered at 1340 nm was observed, which corresponds to the 1 G 4 ? 3 H 5 transition of Pr 3+ . Several spectroscopic parameters for the 1 G 4 ? 3 H 5 transition of Pr 3+ ions were determined. The average product of emission cross section and radiative lifetime were relatively large for all x/65/35 PLZT samples (x=6-10) studied, with values close to 105AE2 (910 À26 cm 2 Ás). These spectroscopic investigations indicate that Pr 3+ /Yb 3+ :PLZT ferroelectric ceramics are promising candidate for efficient sources emitting nearinfrared radiation at 1340 nm. K E Y W O R D Snear-infrared luminescence, PLZT ceramics, rare-earth ions

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