Abstract
The effect of Yb3+ ions on upconversion luminescence and thermal properties of Tm3+/Yb3+ co-doped La2O3-Nb2O5-Ta2O5 glasses has been studied. Glass transition temperature is around 740 °C, indicating high thermal stability. The effect of Yb3+ ions on the thermal stability is not obvious. Both the glass forming ability and the upconversion luminescence first increase and then decrease with the increase of Yb3+ ions. The glasses perform low glass forming ability with ΔT around 55 °C. Blue and red emissions centered around 477, 651, and 706 nm are obtained at the excitation of 976 nm laser. The upconversion luminescence mechanism is energy transfer from Yb3+ to Tm3+ mixed with two- and three- photon processes. The thermal kinetic Differential Thermal Analysis (DTA)-analysis indicates that the average activation energy first increases and then decreases with the increase of Yb3+ ions. This result can be introduced in order to improve upconversion luminescence of glasses by crystallization in the future. Tm3+/Yb3+ co-doped La2O3-Nb2O5-Ta2O5 glasses with good upconversion and thermal properties show promising applications in solid-state laser, optical temperature sensing.
Highlights
Upconversion luminescence from near infrared to visible wavelength in rare earth ions doped glasses has attracted much attention for the promising applications in solid-state visible laser [1], optical temperature sensing [2], optical fiber and amplifier [3], and sea water communication [4].As one typical rare earth ion that can emit blue emissions by upconversion luminescence, Tm3+ ion has been paid close attention recently [5,6,7]
To study the thermal stability and thermal kinetic analysis, Differential Thermal Analysis (DTA) curves of glass spheres were recorded at heating rates of 5, 10, 15, and 20 ◦ C/min in the air by thermal analysis equipment (NETZSCH STA 449C, Selb, Germany)
To study the thermal properties of Tm3+/Yb3+ co-doped La2 O3 -Nb2 O5 -Ta2 O5 (LNT) glasses, glasses with different contents of Yb3+ ions were characterized by DTA
Summary
Upconversion luminescence from near infrared to visible wavelength in rare earth ions doped glasses has attracted much attention for the promising applications in solid-state visible laser [1], optical temperature sensing [2], optical fiber and amplifier [3], and sea water communication [4]. Novel Nb2 O5 -based glasses perform low phonon energy (~735 cm−1 ), high refractive index, good thermal properties, and high transparency, indicating that it can be a favorable candidate for strong upconversion luminescence from Tm3+ /Yb3+ ion pair [8,9,10]. This new glass is prepared without adding any glass network formers. The thermal kinetic DTA-analysis was discussed in order to obtain the activation energy (Ea ) by the Kissinger method In this way, the crystallization process of glasses during the heat treatment can be revealed. This result can be used to be a reference to decide the heat treatment conditions for crystallization to optimize the upconversion luminescence
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