Preparation of Eu~(2+)-doped Ca_2Si_5N_8 by Carbothermal Reduction/Nitridation of Spray-pyrolyzed Oxideitride Powder and Its Luminescence Properties

摘要

The conditions for the preparation of regular-shaped Eu~(2+)-doped calcium silicon nitride ((Ca_(0.99)Eu_(0.01))_2Si_5N_8) powder were examined by the carbothermal reduction and nitridation (CRN) of oxideitride powder prepared by ultrasonic spray pyrolysis. Two kinds of silicon sources, i.e., (i) colloidal silica (CS) and (ii) silicon nitride (Si_3N_4; SN), were used for the spray pyrolysis. Firstly, the solution containing 0.057 mol·dm~(-3) Ca(NO_3)_2, 0.140 mol·dm~(-3)CS and 5.71 × 10~(-4) mol·dm~(-3) Eu(N0_3)_3 was spray-pyrolyzed at 600℃, and the resulting powder was calcined at 800℃ for 10 min in air. The single phase but agglomerated particles of (Ca_(0.99)Eu_(0.01))_2Si_5N_8 were obtained when the CRN (the relative carbon amount to the stoichiometric amount (m): 1.5) of spray-pyrolyzed/calcined oxide powder was conducted at 1300℃ for 2 h in nitrogen (N_2) atmosphere. Secondly, the solution containing 0.0285 mol·dm~(-3)Ca(NO_3)_2, 0.070 mol·dm~(-3)SN and 2.855 × 10~(-4)mol·dm~(-3)Eu(NO_3)_3 (one-half of the solution concentration compared to the case of CS utilization) was spray-pyrolyzed, and the CRN of spray-pyrolyzed oxideitride powder was conducted at 1500℃ for 2 h to obtain (Ca_(0.99)Eu_(0.01))_2Si_5N_8 in N_2 atmosphere. The microscopic observation showed that this powder was composed of regular-shaped particles with sizes of approximately 2-3μm. The excitation and emission peaks of this powder appeared at around 370 and 590 nm, respectively, showing the emission of orange light.