Mixtures of lanthanum oxide, europium oxide, and phosphoric acid were heated with various ratios of P/(La + Eu) and Eu/(La + Eu). The obtained phosphates were estimated using XRD patterns, FT-IR spectra, and SEM images. The fluorescence spectra and resistance against hydrofluoric acid were estimated as functional properties of these phosphate materials. The condensed phosphates showed a strong peak at 615 nm and high resistance against hydrofluoric acid.
An aqueous solution of sodium dihydrogen phosphate was mixed with a aqueous solution of lanthanum nitrate and stirred for 24 h, and the pH was adjusted to 11 using ammonia. The obtained phosphates were analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry-differential thermal analysis, and scanning electron microscopy. The lanthanum phosphate gel was obtained with a large amount of water. The fluorescence of the gels was investigated by substituting a part of the lanthanum cations with cerium, terbium, and europium cations. UV-vis reflectance and fluorescence spectra of these substituted materials were obtained and analyzed. Rrare-earth phosphate gels with large amounts of water exhibited bluish purple, green, and red fluorescence when cation ratios of La/Ce = 70/30, La/Ce/Tb = 55/30/15, and La/Eu = 95/5 were used, respectively.
Europium-substituted lanthanum polyphosphates (Eu; 0, 1, 2, 3, 4, 5, and 10 mol%) were prepared from lanthanum nitrate, europium nitrate, and sodium polyphosphate solutions. The obtained phosphates were estimated using XRD patterns, TG-DTA curves, SEM images, and particle size distributions. The fluorescence spectra were estimated as functional properties of these phosphate materials. The obtained samples crystallized by heating at 600ºC. Lanthanum polyphosphates were stable from 600 to 850ºC. The 5 mol% europium-substituted lanthanum polyphosphate showed a strong peak at 615 nm.
<p class="MsoNormal"> <span lang="EN-US">Mixtures of lanthanum oxide, europium oxide, calcium carbonate, and phosphoric acid were heated with various ratios of P/(Eu</span><span lang="EN-US"> </span><span lang="EN-US">+</span><span lang="EN-US"> </span><span lang="EN-US">La</span><span lang="EN-US"> </span><span lang="EN-US">+</span><span lang="EN-US"> </span><span lang="EN-US">Ca) and La/Ca. Europium ratio was settled at Eu/(Eu</span><span lang="EN-US"> </span><span lang="EN-US">+</span><span lang="EN-US"> </span><span lang="EN-US">La</span><span lang="EN-US"> </span><span lang="EN-US">+</span><span lang="EN-US"> </span><span lang="EN-US">Ca)</span><span lang="EN-US"> </span><span lang="EN-US">=</span><span lang="EN-US"> </span><span lang="EN-US">0.03. The obtained phosphates were estimated using X-ray diffraction (XRD) patterns, Fourier transform infrared spectroscopy (FT-IR) spectra, and scanning electron micrograph (SEM) images. The fluorescence spectra and resistance against hydrofluoric acid were estimated as functional properties of these phosphate materials. The mixture of lanthanum and calcium phosphates were formed from XRD patterns and IR spectra. Samples prepared in P/(Eu</span><span lang="EN-US"> </span><span lang="EN-US">+</span><span lang="EN-US"> </span><span lang="EN-US">La</span><span lang="EN-US"> </span><span lang="EN-US">+</span><span lang="EN-US"> </span><span lang="EN-US">Ca)</span><span lang="EN-US"> </span><span lang="EN-US">=</span><span lang="EN-US"> </span><span lang="EN-US">2 and 3 had large particles in SEM images. The condensed phosphates showed a strong peak at 615 nm and high resistance against hydrofluoric acid.</span> </p>
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