New Synthesis Of Transition Metal Phosphate Luminescent Materials And Study On Their Properties

The transition metal phosphates are novel porous functional materials, and have potential applications as new materials that may have ion exchange, absorption, separation, ionic conductivity, heterogeneous catalytic and interesting optical properties. So the synthesis of transition metal phosphates microporous materials is of extremely important significance. The main work of this paper is as follows:1. The LiZn0.9PO4:Mn0.1H2O was synthesized via solid-state reaction using LiH2PO4·H2O, ZnSO4·7H2O, MnSO4·H2O and Na2CO3as raw materials. XRD analysis showed that the synthesized product was orthorhombic LiZno.9P04:Mn0.1·H2O.Monoclinic LiZn0.9PO4:Mn0.1was a green-yellow emitting phosphor which could be obtained after calcining LiZn0.9PO4:Mn0.1·H2O at600℃. Based on the iterative iso-conversional procedures, the average value of the activation energies associated with the thermal dehydration of LiZn0.9PO4:Mn0.1·H2O was determined to be90.3kJ-mol". Dehydration of the crystal water molecule of LiZn0.9PO4:Mn0.1·H2O was a single-step reaction process. A method of multiple rate iso-temperature was used to determine the most probable mechanism g(a) of the dehydration step. It was Mample single model (g(a)=-ln(1-a)) and was controlled by random nucleation and subsequent growth mechanism. The pre-exponential factor A was calculated on the basis of Ea and g(a). Besides, the thermodynamic functions (ΔS≠, ΔH≠, ΔG≠) of the dehydration reaction of LiZn0.9PO4:Mn0.1·H2O were determined.2. The single phase KZn2(PO4)(HPO4) was synthesized via solid-state reaction at80℃using K3PO4·3H2O, K2HPO4·3H2O and ZnSO4·7H2O as raw materials. XRD analysis showed that KZn2(PO4)(HPO4) was a compound with orthorhombic structure. The thermal decomposition of KZn2(PO4)(HPO4) experienced one step, which was the intramolecular dehydration of the protonated phosphate groups to form Zn2P2O7. The average value of the apparent activation energy Ea associated with the decomposition of KZn2(PO4)(HPO4) was determined to be411.5±14.4kJ·mol-1. A new modified method of the multiple rate iso-temperature was used to define the most probable mechanism g(a)=1-(1-a)1/3.The reliability of the used method for the determination of the kinetic mechanism was tested by the comparison between experimental plots and model results for every heating rate. The results showed that the mechanism function was reliable. The pre-exponential factor A and he thermodynamic functions (ΔS≠, ΔH≠, ΔG≠) were obtained on the basis of Ea and g(a).3. The single phase NH4Co0.9Zn0.1PO4·H2O was synthesized via solid-state reaction using (NH4)3PO4·3H2O, CoCl2·6H2O and ZnSO4·7H2O as raw materials. Based on iterative iso-conversional procedures, the values of apparent activation energies associated with the first stage (dehydration), second stage (deamination) and third stage (condensation) for the thermal decomposition of NH4Co0.9Zn0.1PO4·H2O were obtained and determined to be92.4±4.4,138.7±6.5and286.3±152.2kJ·mol-1, respectively, which demonstrated that the first and second stages were single-step kinetic processes, and the third stage was a kinetically complex process. A model-free method of the multiple rate iso-temperature was used to define the most probable mechanism functions g(a) of the two stages.The reliability of the established mechanisms were tested by the comparison between experimental plots and model result for every heating rate. The values of pre-exponential factor A and thermodynamic functions (ΔS≠, ΔH≠, ΔG≠) of the two stages were obtained on the basis of Ea and g(a).4. The LaPO4:Ce·0.5H2O and LaPO4:Ce,Tb·0.5H2O were synthesized via solid-state reaction using La(NO3)3、(NH4)3PO4·3H2O、Ce2(SO4)3·8H2O and TbCl3as raw materials. Based on the iterative iso-conversional procedures, the average values of the activation energies associated with the thermal dehydration of LaPO4:Ce·0.5H2O and LaPO4:Ce,Tb·0.5H2O were determined. Monocline crystalline LaPO4:Ce and LaPO4:Ce,Tb could be obtained after calcining LaPO4:Ce·0.5H2O and LaPO4:Ce,Tb·0.5H2O at700℃for3h, which had intensive fluorescence property.