Michał Głowacki

A combined study of the equation of state of monazite-type lanthanum orthovanadate using in situ high-pressure diffraction and ab initio calculations.

Lanthanum orthovanadate (LaVO4) is the only stable monazite-type rare-earth orthovanadate. In the present paper the equation of state of LaVO4 is studied using in situ high-pressure powder diffraction at room temperature, and ab initio calculations within the framework of the density functional theory. The parameters of a second-order Birch-Murnaghan equation of state, i.e. those fitted to the experimental and theoretical data, are found to be in perfect agreement - in particular, the bulk moduli are almost identical, with values of 106 (1) and 105.8 (5) GPa, respectively. In agreement with recent reported experimental data, the compression is shown to be anisotropic. Its nature is comparable to that of some other monazite-type compounds. The softest compression direction is determined.

Spectroscopic characterization of SrB4O7:Tm2+, a potential laser material and optical temperature sensor

Polycrystalline samples of SrB4O7:1% Tm2+ were prepared in air by a solid state reaction method. High resolution spectra and decay curves for infrared luminescence related to the intraconfigurational 2F5/2 → 2F7/2 transition and for visible luminescence related to the interconfigurational transition between the lowest energy state of the 4f125d configuration and the ground 2F7/2 state of the 4f13 configuration of Tm2+ were recorded as a function of temperature between 5 and 350 K. Energies of crystal field levels of the 2F5/2 and 2F7/2 multiplets and the 2F5/2 lifetime value were determined from low temperature measurements. With these data room temperature emission and absorption spectra were calibrated in the cross-section units. It was found that the infrared emission in SrB4O7:Tm2+ is long-lived with a lifetime value of 9.5 ms and its spectrum indicates that stimulated emission near 1.18 nm may be feasible. Examination of recorded decay curves for the visible luminescence revealed that the lifetime of the lowest energy state of the 4f125d configuration depends weakly on temperature in the region 5–280 K and then shows a steep decrease when the temperature grows from about 290 K to 350 K. The evaluated values of the thermal sensitivity parameter S for SrB4O7:Tm2+ in the region 300–330 K (27–57 °C) exceed 3.9% per K with a peak at 320 K (47 °C) equal to 6.30% per K. The S value is the highest reported thus far for luminescence thermometers operating in physiological temperatures.

Growth and EPR properties of ErVO4 single crystals

Abstract Single crystals of ErVO4 were grown by the Czochralski method under ambient pressure in a nitrogen atmosphere. Obtained crystals were transparent with strong pink coloring. Electron paramagnetic resonance (EPR) spectra were recorded as a function of the applied magnetic field. Temperature and angular dependences of the EPR spectra of the samples in the 3–300 K temperature range were analyzed applying both Lorentzian––Gauss approximation for diluted medium and Dyson for dense magnetic medium. EPR-NMR program was done to find local symmetry and spin Hamiltonian parameters of erbium ions.

Phase Transition In Perovskite LaGaO3 Crystals Doped With Sr And Mn : Studied By Raman Spectroscopy

In recent years perovskite-type LaGa1-xBxO3 (where B = Mg, Mn) compounds have been the subject of extended investigations because of either the potential technological applications or the basic interest in solid state physics due to the existence of phase transition [1,2]. Lanthanum gallates doped with Sr and Mn or other transition metal elements are good candidate as anode materials for LSGM-based SOFCs. This paper concerns the investigations LaGaO3 crystals doped with Sr and Mn ions carried out using Raman spectroscopy. Single crystals of LaGaO3 doped with Sr and Mn (LSGMn) were grown by the Czochralski method from the melt with compositions: La1-xSrxGa1-yMnyO3, x = 0.05 y = 0.06, x = 0.075 y = 0.09 and x = 0.1 y = 0.12.