Thermal and spectral behavior of (Y,Eu)VO4 powder

Autor: N. A. Harabor, Ana Harabor, Petre Rotaru
Rok vydání: 2012
Předmět:
Zdroj: Journal of Thermal Analysis and Calorimetry. 111:1211-1219
ISSN: 1572-8943
1388-6150
Popis: Thermal analysis of YxEu1−xVO4 powder (used as “phosphor” coating for a high pressure mercury lamp) was done under a non-isothermal linear regime, both in a dynamic air regime and in a nitrogen atmosphere. The heating in air atmosphere gave on TG curve small rate of mass increase due to oxygenation and two endothermic effects are observed on DTA and DSC curves. By contrary, in nitrogen atmosphere a continuous stepped mass loss of powder (around 0.65 %), is recorded in the range of temperatures from room temperatures to 1,200 °C, and only one endothermic effect, to eliminate the gases accumulated on the crystallite surface. The powder was heated for 3 h in a Nabertherm furnace at 350, 800, and 1,100 °C using quite similar rate for heating program followed by a furnace cooling to room temperature. XRD and FTIR analyses showed the sample purification by thermal treatment and a very small increase of nanocrystallite sizes. The time evolution of the optical emission spectra in the range from 186.2 to 877.47 nm were recorded for different lamp powers in two different situations: with the outer bulb coated with YxEu1−xVO4 type “phosphor”, and without it. We observed that UV-Hg lines are absorbed by YxEu1−xVO4 type “phosphor” with different percents (100 % for 253.73 nm, 95 % for 312.65 nm, and 33 % for 365.12 nm) but the heating of the powder do not influence the UV-absorption properties of the powder.
Databáze: OpenAIRE
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