The effect of Mg incorporation on structural and optical characteristics of rhombohedral Zn 2 GeO 4 doped with manganese was systematically studied, fixing the concentration of manganese at 2 atom %. The phosphors were prepared by a high-temperature solid-state-reaction technique. The structural properties were studied using X-ray diffraction ͑XRD͒ and optical properties were characterized by diffuse reflectance spectra ͑DRS͒, photoluminescent excitation ͑PLE͒, and photoluminescent ͑PL͒ emission spectra. The XRD and DRS analyses reveal that Mg can be successfully alloyed in Zn 1.96−1.96x Mg 1.96x GeO 4 :Mn 0.04 up to x = 0.30 and forms a solid solution. The PL emission was maximum when 5 atom % Zn was replaced with Mg in comparison to an Mg-free Zn 1.96 GeO 4 :Mn 0.04 sample. The mechanism of luminescence is identified as resonant transfer from a subbandgap state in the host to Mn 2+ . The PLE and DRS spectra of Zn 1.96−1.96x Mg 1.96x GeO 4 :Mn 0.04 ͑0 ഛ x ഛ 0.5͒ exhibited a blue shift with an increase in Mg concentration. The cell volume was found to be a monotonously increasing function of Mg concentration up to x = 0.25, beyond which it varied randomly.
Nanoparticles of
ZnnormalGa2normalO4
and Eu-doped
ZnnormalGa2normalO4
were hydrothermally synthesized varying the process parameters, such as the volume ratio of the cation precursor solutions, temperature and time of growth, and dopant concentration. The nanoparticles were structurally characterized by X-ray diffraction, high-resolution transmission electron microscopy, and selected-area electron diffraction. The studies confirmed the formation of spherically shaped
ZnnormalGa2normalO4
nanoparticles with the standard spinel structure. Photoluminescence (PL) studies show that Eu-doped
ZnnormalGa2normalO4
nanoparticles exhibits a sharp red luminescence due to the intra-4f transitions of
Eu3+
ions at an excitation of
397nm
. Luminescence quenching is observed in the nanoparticles at higher Eu concentration. The room-temperature PL measurements of pure
ZnnormalGa2normalO4
nanocrystals monitored at an excitation wavelength of
254nm
gave a peak-shaped spectrum instead of the normally observed bell-shaped spectrum of bulk
ZnnormalGa2normalO4
. The bandgap of the
ZnnormalGa2normalO4
nanoparticles is blueshifted compared to the bulk material due to quantum confinement effects. Incorporation of Eu in the nanoparticles was confirmed by inductively coupled plasma atomic emission spectroscopic studies.
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