Zhi-yong Mao

Fabrication of amorphous phase encrusted oxynitride phosphor with white-light emission via in situ penetration

White-light emission is realized through assembling a blue-emitting amorphous phase on a yellow-emitting Ca-SiAlON: Eu2+ phosphor particle in the form of a coating. The variation of the yellowish–white–blue color is traced with the control of a blue-emitting coating formed via in situ penetration of silicon oxide into a Ca-SiAlON network.

SiAlON-based crystal–glass composite phosphor with tunable yellow-green-blue color emission induced by SiO2 melting corrosion

SiAlON-based crystal–glass composite phosphors with tunable yellow-green-blue emission are exploited. Substitution of Al–N by Si–O in a SiAlON lattice and the introduction of a Si–Al–O–N glass phase are induced by melting corrosion as SiAlON polycrystal powders were heat-treated with nano-SiO2 additive. The melting corrosion process involving liquid penetration, solid dissolution, liquid transportation is discussed and assigned to the origin of morphology transformation. The substitution extent and the glass content are identified to increase with the addition of nano-SiO2 additive. The resultant tunable photoluminescence of Eu2+ in the SiAlON lattice and Si–Al–O–N glass matrix and the microstructure evolution are detailed, respectively. The emission color of the SiAlON-based crystal–glass composite phosphors is traced continuously from yellow to green then to blue with the combination of changeable emissions of Eu2+ originated from the SiAlON phase and glass phase. This artful SiAlON-based crystal–glass composite phosphor shows flexible color-adjustable capability with the control of SiO2 melting corrosion, indicating the potential applications in lighting and display fields.

Investigation of Al-doped silicon nitride-based semiconductor and its shrinkage mechanism

An Al-doped silicon nitride-based semiconductor is successfully synthesized by the chemical vapor deposition (CVD) technique. Optical, electrical and electronic properties are investigated in detail which reveal that Al-doped α-Si3N4 presents a typical semi-conductive character with a band-gap of 2.65 eV and an electrical conductivity of ∼6.11 × 10−2 S cm−1. Al-doping complex (substitutional accompanied with interstitial Al ions in the (102) plane) in α-Si3N4 lattice and its resulting abnormal crystal growth property are discussed. Experimental and theoretical calculation results indicate that this peculiar Al-doping complex in the (102) plane is responsible for the shrinkage of the band-gap for Al-doped α-Si3N4. The presented results demonstrate that this Al-doped α-Si3N4 may open up many applications opportunities in optics, electronics and photoelectronics fields.

Multi-wavelength excitable europium-doped borosilicate glasses for orange-red emission: composition-induced structure and valence variation

Abstract Europium-doped borosilicate glasses were prepared by melt-quenching procedure in the air. The mixed valence of Eu 2+ and Eu 3+ was identified by photo luminescence spectrum and electron paramagnetic resonance (EPR). The existence of mixed valence was observed owing to the unequivalent substitution and de-polymerization network of the as-prepared borosilicate glasses. The variation of the glass composition in B 2 O 3 /BaO ratios changed the stability of the Eu 3+ ions distinctly. In particular, as-prepared borosilicate glasses exhibited a tri-wavelength light excitable spectra centered at 397, 466 and 534 nm to give the broadened orange-red emission at around 592 and 617 nm, due to supersensitive transitions of Eu 3+ ions. This simultaneous tri-wavelength excitation happened to correspond with the emitting wavelength from near ultraviolet, blue AlInGaN chips and that from YAG:Ce 3+ . The total quantum yield (QY) of the Eu-doped glasses under 466 nm excitation was evaluated to be 10%, potentially providing a versatile combination with the europium-doped borosilicate glasses for red component addition to improve the quality of white light.