Luminescence of Eu ^(3+) in LnAlO_3 (Ln=Gd,Y) under UV and VUV Excitation

Single phases of LnAlO 3:Eu 3+ (Ln=Gd,Y) were obtained by the process of evaporation of their nitric acid solution, and then pyrolysis of their nitrate salts. On monitoring by 613 nm emission, broad bands at around 270 and 170 nm were observed in the excitation spectrum of Gd 0.95Eu 0.05AlO 3. These peaks could be assigned to charge transfer (CT) transitions of Eu 3+-O 2- and Gd 3+-O 2- respectively. All the transitions observed in Gd 0.95Eu 0.05AlO 3 are faithfully reproduced in the Y 0.95Eu 0.05AlO 3, but with an exception of the 8S 7/2→ 6I 11/2 transition of Gd 3+. The 153 nm broad band could be the CT transition of Y 3+-O 2-. Accordingly, the efficiency luminescence of (Gd,Y)BO 3:Eu 3+ was explained as a result of CT transitions of Gd 3+-O 2- and Y 3+-O 2- under 147 nm excitation. Under VUV excitation, Gd 0.95Eu 0.05AlO 3 exhibits a bright red luminescence with CIE chromaticity coordinates of (0.623, 0.335) with a PL intensity of 30 of the commercial phosphor (Gd,Y)BO 3:Eu 3+ (KX-504A). The PL spectrum of Y 0.95Eu 0.05AlO 3 is similar to that of Gd 0.95Eu 0.05AlO 3. Calculation of the color coordinates gives x=0.636, y=0.340 with a PL intensity of 50 of the (Gd,Y)BO 3:Eu 3+ (KX-504A) for Y 0.95Eu 0.05AlO 3, and confirms that it has the appearance of pure spectral red, corresponding approximately to 608 nm. It can be concluded that LnAlO 3:Eu 3+ is a promising red VUV phosphor.

Band-gap engineering of La1-xNdxAlO3(x = 0,0.25,0.50,0.75,1)perovskite using density functional theory：A modified Becke Johnson potential study

The structural,electronic,and magnetic properties of the Nd-doped Rare earth aluminate,La1-xNdxAlO3（x = 0%to 100%） alloys are studied using the full potential linearized augmented plane wave（FP-LAPW） method within the density functional theory.The effects of the Nd substitution in La AlO3 are studied using the supercell calculations.The computed electronic structure with the modified Becke–Johnson（m BJ） potential based approximation indicates that the La1-xNdxAlO3 alloys may possess half-metallic（HM） behaviors when doped with Nd of a finite density of states at the Fermi level（EF）.The direct and indirect band gaps are studied each as a function of x which is the concentration of Nddoped La AlO3.The calculated magnetic moments in the La1-xNdxAlO3 alloys are found to arise mainly from the Nd-4f state.A probable half-metallic nature is suggested for each of these systems with supportive integral magnetic moments and highly spin-polarized electronic structures in these doped systems at EF.The observed decrease of the band gap with the increase in the concentration of Nd doping in La AlO3 is a suitable technique for harnessing useful spintronic and magnetic devices.

New Process of Fine Grinding-activation of Heavy CaCO_3 and Its Application to PVC Rigid Sheet

To make heavy calcium carbonate filled UHMW PVC rigid sheet, the calcium carbonate powder is activated in a specially designed fine grinding activation equipment (SM 10) by adding rare earth aluminate coupling agent. The calcium carbonate powder is ground to micron order. The activated calcium carbonate filler shows excellent properties when it is added to UHMW PVC, since the activated powder surface has strong compatibility with polymer. At a filling rate of 70 [KG-*3/4]phr (per hundred resin), the impact strength with U notch is above 7kJ/m 2 and the tensile strength is above 20 MPa. The fine grinding activation and PVC sheet pressing process are given. Both the influence of the amount of plasticizer and coupling agent on the mechanical properties and the influence of filling rate on PVC rigid sheet are discussed.