LaPO4:Er microspheres with high NIR luminescent quantum yield

Abstract

Er-doped LaPO 4 micro-spheres have been synthesized by spray pyrolysis and the near infrared (NIR) properties have been characterized. It has been found that, following an adequate post-annealing treatment, the emission properties are remarkably improved. The NIR luminescence intensity is highly enhanced and its decay time increases to a value almost coincident with the reported radiative lifetime, which implies that the quantum yield approaches   100%. This improvement in luminescence characteristics is probably related to the suppression of residual OH -radicals, that otherwise act as NIR luminescence quenchers, and to the increase in material's crystallinity. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 *Manuscript Click here to view linked References 1.-INTRODUCTIONLanthanide phosphate (LaPO 4 ) and, in particular, its monoclinic polymorph (monazite), has been widely used as a host for the preparation of lanthanide-based phosphors. In fact, doped with Ce and Tb constitutes one of the classical phosphors used in high-quality fluorescent lighting due to its high quantum yield and stability at high temperature [1][2][3][4]. By varying the dopants (Pr, Nd, Eu, …) the optical properties can be tuned over a wide spectral range, with emerging applications in different fields such as biomedicine [5][6], photonic band gap materials or optical amplification [7][8]. In particular, for optical amplifiers and lasers, Er becomes the most interesting dopant because of its characteristic emission, at around 1.5 m, coincident with the transparency window of optical fibers [8][9]. Along this line, there has been a considerable effort along the last years in order to prepare Er doped phosphate particles incorporated into polymer-based components, in order to improve luminescence characteristics and trying to achieve long lifetimes and high quantum efficiencies [10][11][12][13][14][15][16][17]. The data reported in the literature for the 1.5 m emission lifetime vary within a very large range (60 s [14] to 3.7 ms [17]), reflecting possibly the large variety of dopants concentration, particle size and fabrication processes; affecting material's properties such as crystallinity or impurities content [10][11][12][13][14][15][16][17].Spray pyrolysis is a well known technique for the synthesis of powdered materials, whose main advantages are simplicity and continuous character, which, along with its suitability to control particle size (micrometric) and shape (spherical), make it very attractive for industrial purposes [18][19]. Recently, this method has been used to prepare LaPO 4 spheres doped with Ce and Tb ions, which showed a high luminescence efficiency after a post heating treatment at >1300ºC [20][21]. However, up to our knowledge, this synthesis method has never been applied to the synthesis of Er-doped LaPO ...

Preparation of LaPO 4 :Ce 3+ ,Tb 3+ nanophosphors by mixed co-precipitation process and their photoluminescence properties

“…Lanthanum orthophosphate (LaPO 4 ), which belongs to two crystalline structures: the monoclinic monozite type (for Ln=La to Gd) and the quadratic xenotime type (for Ln=Tb to Lu), has been showing to be an attractive host lattice for lanthanide ions to prepare phosphors that emit in a broad range of colors [8,9]. LaPO 4 phosphors doped with different types of rare-earth ions, such as Eu 3 þ , Ce 3 þ , Tb 3 þ , Er 3 þ , Dy 3 þ , Sm 3 þ , Yb 3 þ and Pr 3 þ , have been reported in the literatures [9][10][11][12][13][14][15][16]. Among all these orthophosphate-type phosphors, trivalent cerium (Ce 3 þ ) and terbium (Tb 3 þ ) co-activated LaPO 4 (LaPO 4 :Ce 3 þ ,Tb 3 þ ) phosphors are prominent because of the high-efficiency energy transfer between Ce 3 þ and Tb 3 þ , and the property stability at high temperatures.…”

Effects of pH value on growth morphology of LaPO4 nanocrystals: investigated from experiment and theoretical calculations

“…Doped with other rareearth elements, bulk LaPO 4 products were commercially applied in lamp phosphors [2], high-temperature proton conductors [3] and biolabeling materials [4]. Due to different starting materials, synthesis methods and technological parameters, the resultants present a variety of morphologies, such as fiber [5], rodlike [6], sphere [7], flowerlike [8] and nanotube [9].…”

Preparation and luminescence properties of color-tunable single-phased LaPO4:Eu3+/Tb3+ phosphors

“…For example, Tb 3+ doped LaPO 4 is an excellent down-conversion material and can emit green light under UV excitation, which has been widely used as a fluorescent green phosphor [13][14][15] . Eu 3+ doped LaPO 4 red phosphor material has high luminous efficiency, and has become one of focuses of many rare-earth doped materials [16] .…”