Mechanism of Phase Transformation and Formation of Barium Hexafer rite Doped with Rare-Earths in Sol-Gel Process

The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La 3+ were studied by chemical p hase analysis, X-ray diffraction and infrared spectrometry analysis. The expe rimental results show that phase transformation reactions of FeCO 3, Fe 2O 3 and BaFe 2O 4, barium hexaferrite and γ-Fe 2O 3 take place in the heat tr eatment of gel. While the doping lanthanide ion replace barium ion, an equivalen t quantity of Fe 3+ are reduced to Fe 2+ to maintain the charge equili brium.

Preparation, Characterizations and Magnetic Properties of Doped Barium Hexaferrites BaFe_(12-2x)Mn_xSn_xO_(19) (x = 0.0-1.0)

A series of doped barium hexaferrites BaFe12-2xMnxSnxO19 （x = 0.0-1.0） particles were prepared by the co-precipitation/molten salt method. The particle size and crystalline of the samples BaFe12-2xMnxSnxO19 decrease with an increase in the doping amount x. When x is less than 0.8, the pure BaFe12-2xMnxSnxO19 particles with hexagonal plate morphology are obtained. The effects of substitution on magnetic properties were evaluated and compared to nomal BaFe12O19. The specific magnetizations （Ms） of doped materials have been significantly improved. Among all these compositions, the BaFe10.4Mn0.8Sn0.8O19 sample has the highest Ms value of 81.8 A？m2？kg-1 at room temperature and its intrinsic coercivity （Hc） is 44.5 kA？m-1. The as-prepared doped barium ferrites exhibit a low temperature coefficient of coercivity close to zero. The coercivity is independent of temperature when x is in the a range 0.5-0.7.

Thermoluminescence of BaFCl_xBr_（1－x）：Sm System and Assignment of Their Glow Peaks

Through the study of the thermoluminescence(TL) of BaFClxBr1-x: Sm(0<x<1) system, it is found that former assignment of the glow peaks of BaFX(X = Cl, Br) is plausible. Through detailed study by several methods and techniques, a correct assignment is given in this paper, i.e. the first, second, and third glow peaks of BaFClxBr1-xSm are assigned to F(F-), F(Cl-), F(Br-) centers respectively, and the first andsecond glow peaks of BaFX are assigned to F(F-) and F(X-) centers respectively. This results are confirmed by theoretical consideration. Possible reasons for former plausible assignment are also pointed out here.

Simultaneous structure and luminescence property control of barium carbonate nanocrystals through small amount of lanthanide doping

Rare earth doping has been widely applied in many functional nanomaterials with desirable properties and functions,which would have a significant effect on the growth process of the materials.However,the controlling strategy is limited into high concentration of lanthanide doping,which produces concentration quenching of the lanthanide ion luminescence with an increase in the Ln^(3+)concentration,resulting in lowering the fluorescence quantum yield of lanthanide ion.Herein,for the first time,we demonstrate simultaneous control of the structures and luminescence properties of BaCO_3nanocrystals via a small amount of Tb^(3+)doping strategy.In fact,Tb^(3+)would partially occupy Ba^(2+)sites,resulting in the changes to the structures of the BaCO_3nanocrystals,which is primarily determined by charge modulation,including the contributions from the surfaces of crystal nuclei and building blocks.These structurally modified nanocrystals exhibit tunable luminescence properties,thus emerging as potential candidates for photonic devices such as light-emitting diodes and color displays.