Spectroscopic investigation on Europium (Eu3+) doped strontium zinc lead phosphate glasses with varied ZnO and PbO compositions

https://doi.org/10.1016/j.jnoncrysol.2020.120322Get rights and content

Highlights

  • Eu3+ doped SrZnPb phosphate glasses with varying ZnO and PbO contents are prepared.

  • XRD, FTIR, absorption, phonon SB, emission, decay and CIE coordinates are studied.

  • Emission intensities increase with increasing ZnO and decreasing PbO compositions.

  • Decay lifetime and colour purity increase as ZnO increases and PbO decreases.

  • Strong red emission at 611 nm can be utilized as laser and luminescent materials.

Abstract

A series of europium (Eu3+) doped SrO + ZnO + PbO + P2O5 glasses with varied ZnO and PbO compositions have been prepared by melt quenching method. The structural and optical properties of the samples are analysed by XRD, FTIR, absorption, optical band gap energy, excitation, phonon sideband (PSB) spectrum, luminescence emission, decay profile and CIE chromaticity coordinates. The most intense emission is found at 611 nm (red) corresponding to 5D0  →  7F2 transition. Using the luminescence emission spectra, the branching ratio (βm), effective bandwidth (Δλeff) and emission intensity ratio (R) have been calculated. The decay profile of the 5D0 excited state is fitted with a single exponential function and thereby lifetime is evaluated. The high colour purity of 97.4% in the red region is estimated for the EuSr30ZnPbP glass. The luminescence properties indicate that the present glasses could be used for red laser materials and optical display devices.

Introduction

The rare earth europium incorporated glasses have been paid growing attention for the devolvement of optical devices, colour displays, optical amplifiers, optical communications, phosphors, holographic image storing, bio-medical applications, light-emitting diodes, white light generation, lasers, thermo-luminescent materials and so on [1], [2], [3], [4], [5], [6], [7], [8], [9].

Amongst the lanthanide elements, the trivalent europium (Eu3+) is one of the best elements for doping due to its narrow emission band, excellent red emission efficiency, strong emission intensity and long lasting excited-state lifetime [5,10,11]. The electronic transition of europium (Eu3+) originates due to partially filled 4f shell (4f6 → 4f6) transition. Europium (Eu3+) doped glasses are widely utilized as red-emitting materials for 5D0 → 7F2 transition. Amongst the possible host materials, phosphate-based glasses are very promising for doping of rare earth ions due to low melting temperature, high transparency and low production cost. Phosphate-based glasses are bio-degradable, biocompatible and they are hygroscopic [1,4,8]. The ZnO acts as a network modifier in the glass system and it reduces hygroscopic character, as well as increases mechanical strength. Addition of zinc oxide in phosphate glasses reduces phonon energy, increases transparency in the UV-Visible region and also increases solubility of the rare-earth ions in the host matrix [5,6,8]. The heavy metal oxides such as PbO and ZnO based glasses find immense applications in the fields of glass ceramics and photonics [10]. Incorporation of PbO in the host glass reduces the phonon energy of the glass which increases the fluorescence properties in the glasses [12]. Several research works have been done on the luminescence properties of europium doped lead phosphate glasses. It is to be mentioned here that the quality of the glass host is improved by the inclusion of the alkaline oxide SrO, since it works as a modifier and increases the thermal stability of the glass systems [1,10,15].

In this context, here we report an investigation on the optical and structural characteristics of the 1 mol% Eu2O3 + 5SrO+ (10+x) ZnO + (25-x) PbO + 59P2O5, (denoted as EuSrZnPbP glasses, x = 0, 10,20), with compositional dependency on zinc oxide (ZnO) and lead oxide (PbO). The detailed analysis on the structural aspect by XRD and FTIR, and the optical properties by means of absorption, optical band gap, photoluminescence, phonon side band, decay profile and CIE 1931 colour chromaticity of the present glasses have been carried out.

Section snippets

Sample preparation

Europium (Eu3+) doped strontium zinc lead phosphate glasses (hereafter, named as EuSrZnPbP) with following compositions have been synthesized:

EuSr10ZnPbP: 1Eu2O3+ 5SrO+ 10ZnO+ 25PbO+ 59P2O5

EuSr20ZnPbP: 1Eu2O3+ 5SrO+ 20ZnO+ 15PbO+ 59P2O5

EuSr30ZnPbP: 1Eu2O3+ 5SrO+ 30ZnO+ 5PbO+ 59P2O5

The glass samples were prepared by mixing appropriate molar (wt.) percentage quantities of the chemicals of high purity available in the market, viz., Eu2O3 (make: Sigma Aldrich, purity 99.9%), SrCO3 (make: Rankem

XRD spectrum

The X-ray diffraction patterns of the three EuSrZnPbP glasses are similar. The XRD profile of the EuSr30ZnPbP glass is plotted in Fig. 1. The XRD profile does not reveal any sharp crystalline peak. The diffraction pattern verifies that the prepared glass is amorphous.

FTIR spectra

The Fourier transform infrared spectra of the EuSrZnPbP glasses at room temperature are presented in Fig. 2. The data of the IR spectra are very significant to analyse the surrounding structure and dynamical disorder of the glass

Conclusions

Europium (Eu3+) doped SrO + ZnO + PbO + P2O5 glass samples are prepared by melt quenching method. The structural properties of the EuSrZnPbP glasses are studied by XRD and FTIR spectra. The glassy nature has been confirmed by XRD patterns. The FTIR techniques identify that different structural phosphate groups are present in these glasses. Optical properties of the EuSrZnPbP glass samples have been analysed by absorption, photoluminescence, phonon side band, decay measurement and CIE

CRediT authorship contribution statement

Ashoke Maity: Investigation, Formal analysis, Writing - original draft. Samar Jana: Conceptualization, Methodology, Writing - review & editing, Supervision, Visualization. Sourav Ghosh: Investigation. Subhash Sharma: Validation.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The corresponding author Dr. Samar Jana expresses thanks to the Department of Science and Technology, Science and Engineering Research Board (DST-SERB), Government of India, for providing financial support for this research work by sanctioning the DST-SERB project (File No. EMR/2016/003103 dated March 2nd, 2017).

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