The conditions for the preparation of regular-shaped Eu
2+-doped calcium silicon nitride ((Ca
0.99Eu
0.01)
2Si
5N
8) powder were examined by the carbothermal reduction and nitridation (CRN) of oxide/nitride 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·m
-3 Ca(NO
3)
2, 0.140 mol·dm
-3CS and 5.71 x 10
-4 mol·dm
-3Eu(NO
3)
3 was spray-pyrolyzed at 600°C, and the resulting powder was calcined at 800°C for 10 min in air. The single phase but agglomerated particles of (Ca
0.99Eu
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°C for 2 h in nitrogen (N
2) atmosphere. Secondly, the solution containing 0.0285 mol·dm
-3Ca(NO
3)
2, 0.070 mol·dm
-3SN and 2.855 x 10
-4mol·dm
-3Eu(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 oxide/nitride powder was conducted at 1500°C for 2 h to obtain (Ca
0.99Eu
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 2-3 μm. The excitation and emission peaks of this powder appeared at around 370 and 590 nm, respectively, showing the emission of orange light.
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