Elsevier

Optical Materials

Volume 47, September 2015, Pages 231-236
Optical Materials

The influence of Pr3+ content on luminescence and optical behavior of TeO2–WO3–PbO–Lu2O3 glass

https://doi.org/10.1016/j.optmat.2015.05.028Get rights and content

Highlights

  • Good stability TeO2–WO3–PbO–Lu2O3 glass as a new host for Pr3+ ions.

  • Luminescence intensity reaches a maximum at Pr3+ ion concentration of about 1020  cm−3.

  • Cross relaxation and energy migration processes are responsible for concentration quenching of luminescence.

Abstract

We have investigated the thermal and spectroscopic properties of Pr3+-doped new tellurite matrix with the molar composition 60%TeO2–27%WO3–10%PbO–3%Lu2O3 (TWPLu). The differential thermal analysis has shown that addition of Lu2O3 to the glass results in an increasing resistance against crystallization. The ellipsometric data have provided a Sellmeier-type dispersion relations of the refractive index of the investigated glasses. The optical absorption edge of the TWPLu matrix has been described within the Urbach approach, while the absorption and fluorescence spectra of the Pr3+-doped TWPLu glasses have been analyzed in terms of the standard Judd–Ofelt theory along with the luminescence decay of the 3P0 and 1D2 levels of the Pr3+ ion. A significant influence of the Pr3+ ion concentration on the photoluminescence intensity as well as on decrease of the lifetimes of both levels has been explained by a non-radiative energy transfer between the ions through cross-relaxation and energy migration processes.

Introduction

In recent years, tellurite glasses doped with lanthanide ions as luminescence centers incorporated into different hosts have attracted much attention due to promising applications in optoelectronics and photonics (see recent review papers [1], [2], [3] and Refs. therein). Tellurite glasses containing, apart from TeO2 also PbO and other oxides, are characterized by a high refractive index (above 2) and a relatively low phonon energy (600–850 cm−1) [4], [5]. Despite of good optical properties, these glasses demonstrate a strong exothermal event during heating that is connected with TeO2 and PbO crystallization [6], [7].

One of the methods to improve the thermal stability of tellurite glasses is addition of lathanide oxides, such as La2O3 or Lu2O3, with the 4f shell of La3+ and Lu3+ ions completely empty and completely filled, respectively, and making these ions optically inactive. Adding La2O3 to the basic TeO2–WO3–PbO glass, an improved glass matrix with the molar composition 60%TeO2–27%WO3–10%PbO–3%La2O3 (TWPLa) has been obtained that appears to be a suitable host for optically active lanthanide ions as demonstrated in our previous works for Nd3+ and Er3+ [8], and Pr3+ ions [9].

Adding Lu2O3 (instead of La2O3) to the basic TeO2–WO3–PbO glass, we have prepared a new matrix with the molar composition 60%TeO2–27%WO3–10%PbO–3%Lu2O3 (TWPLu) and in this work we report on the spectroscopic properties of Pr3+ ions of various concentrations embedded in this host.

The glass transition temperature and resistance of the investigated glasses against crystallization have been determined by performing differential thermal analysis (DTA) measurements.

The absorption- and luminescence spectra as well as radiative decay times of Pr3+ ions in the TWPLu matrix have been analyzed within the standard Judd–Ofelt theory taking into account dispersion of the refractive index obtained from ellipsometric measurements.

Section snippets

Experimental

The host glasses with the molar composition 60%TeO2–27%WO3–10%PbO–3%Lu2O3 (TWPLu) were obtained by melting 16.67 g batches of the high-purity (99.99%) chemicals in gold crucibles in an electric furnace at 850 °C in the air atmosphere. The crucibles were covered with a platinum plate to avoid vaporization losses. Then the melts were poured onto plates preheated to 400 °C, forming a few mm thick layers subsequently annealed in the temperature range 320–340 °C. The density of the TWPLu matrix has been

Thermal properties

Apart from samples from Table 1 we have also studied, for comparison, the thermal behavior of the glass without Lu2O3, i.e. the composition 60%TeO2–30%WO3–10%PbO (TWP), and Fig. 1 shows the DTA curves for all the investigated glasses.

During heating, the studied glasses demonstrate thermal effects characteristic for a typical glassy material and evolution of characteristic temperatures, such as glass transition temperature (Tg) and crystallization temperature (Tcryst), with the glass composition

Conclusions

It has been shown that the TeO2–WO3–PbO–Lu2O3 glass, characterized by high refraction index (n > 2) and sufficient glass stability, can be a suitable host for Pr3+ ions of various concentrations. Applying the standard Judd–Ofelt (J–O) theory to the absorption spectrum of sample TWPLuPr-1, the J–O intensity parameters Ω2, Ω4 and Ω6 have been estimated as being equal to 6.72-, 2.21- and 5.74 × 10−20 cm2, respectively. From photoluminescence (PL) studies it follows that the overall intensity reaches a

Acknowledgment

This work was supported by the Statutory Activities No. 11.11.160.365 (2015) of Faculty of Materials Science and Ceramics, AGH – University of Science and Technology, al. Mickiewicza 30, 30-059 Cracow, Poland.

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