Preparation of red nitride phosphor from powder mixture of metal nitrides using spark plasma sintering

摘要

A red nitride phosphor with a chemical formula: (Sr_(0.8)Ca_(0.2))AlSiN_3: Eu_(0.0075)~(2+) was successfully synthesized using spark plasma sintering at a temperature of 1680 °C from powder mixture of metal nitrides of Sr, Ca, Al, and Si and europium (III) oxide. The prepared phosphor showed a wide excitation band ranging from 300 to 550 nm and a broad emission band centered at a wavelength of about 618 nm, being suitable for use in down-conversion white LEDs. The effects of sintering temperature, holding time as well as uniaxial pressure on phosphor characteristics were investigated. Increasing the sintering temperature increased the crystallization and PL characteristics of the phosphor. The excitation and emission intensity of the phosphor was also affected by the holding time at the maximum temperature. When the synthesis was carried out at 1680 °C and 30 MPa, the optimal holding time was around 30 min. Increasing the uniaxial pressure resulted in the improvement of the excitation and emission intensity. The optical properties of the phosphor synthesized at an increased uniaxial pressure of 42 MPa (1680 °C for 30 min) was comparable to those of the commercial phosphor. The experimental results indicated that the spark plasma sintering method is a viable method to prepare nitride phosphors at relatively low temperatures in short synthesis time, compared to conventional methods.