Synthesis and luminescence properties of Er3+ doped Y(OH)3, NH4Y3F10, and YF3 nanocrystals.

Y(OH)3:Er3+ nanowires were synthesized by a hydrothermal method. Y(OH)3:Er3+ can convert into NH4Y3F10:Er3+ after fluorization, and NH4Y3F10:Er3+ can convert into YF3:Er3+ after being annealed. The structures of obtained Y(OH)3:Er3+, NH4Y3F10:Er3+, and YF3:Er3+ samples were pure hexagonal, cubic, and orthorhombic phase, respectively. Under 378-nm excitation, the three samples showed similar features. The 2H9/2, --> 4I15/2, 4F3/2(4F5/2) --> 4I15/2, and 4S3/2 --> 4I15/2 were observed, and the most intense peak was centered at 436 nm [4F3/2(4F5/2) --> 4I15/2]. Under 980-nm excitation, only the upconversion emissions from NH4Y3F10:Er3+ and YF3:Er3+ were observed. These emissions come from the following transitions: 2H11/2 --> 4I15/2, 4S3/2 --> 4I15/2, and 4F9/2 --> 4I15/2. The upconversion mechanism is discussed in detail.