A series of polycrystalline Li₃Ba₂La_3−xEu_x(MoO₄)₈ samples were prepared by the conventional solid-state reaction. The phase formation of the samples was investigated by X-ray diffraction measurements. The luminescence spectra and decay curves were studied as a function of Eu³⁺ concentration and temperature. It turned out that the optical band gap of the undoped molybdates is at 3.65 eV. The quantum efficiency (QE) of the Eu³⁺ doped luminescent materials increases with increasing Eu³⁺ concentration and almost 100% QE was obtained for those samples doped with 70, 80, or 90% Eu³⁺. A sample containing 100% Eu³⁺ showed solely a slight decrease in quantum efficiency. The luminous efficacy (LE) was 330 and 312 lm W_opt ⁻¹ for the 10 and 100% Eu³⁺ doped samples, respectively. The decrease of LE values is caused by a slight shift of the colour point to the red spectral range with increasing Eu³⁺ content. Temperature dependent measurements revealed that Li₃Ba₂Eu₃(MoO₄)₈ loses only 15% of efficiency up to 400 K, which demonstrates that the investigated phosphors are attractive for application in pcLEDs.

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.