Spectroscopic characterizations of Er doped LaPO4 submicron phosphors prepared by homogeneous precipitation method

• Trivalent Er doped LaPO4 submicron phosphors are successfully synthesized by homogeneous precipitation method.
• Detailed spectroscopic characteristics were done using various experimental and theoretical methods.
• Radiative quantum yield of 96% was obtained for the 1554 nm emission by theoretical calculation.
• A quantum yield of 11% was measured for 1554 nm emission under 12 W/cm2 power density at 980 nm excitation.

Hexagonal shaped LaPO4 submicron particles doped with various concentrations of Er were successfully prepared by homogenous precipitation method using metal nitrates and ammonium phosphate. Particles of approximate particle size 125 nm and size distribution of 85 nm are obtained with good crystallinity. After heat treatment at 1200 °C for 2 h, the particles are characterized for their various optical properties such as absorption, emission, fluorescence decay and optical band gap. Optical absorption and emission data are numerically analyzed with the help of Judd–Ofelt model to evaluate various radiative spectral properties such as radiative decay rates, radiative quantum yield, emission cross-section and fluorescence branching ratios of various emission transitions. Though the radiative quantum yield of 1554 nm emission approaches the theoretical limit of 100%, the experimentally measured quantum yield is only 11% at 12 W/cm2 at 980 nm excitation power density in 2% Er doped LaPO4.