Flower-like morphology of blue and greenish-gray ZnCoxAl2-xO4 nanopigments

• ZnCoxAl2 − xO4 nanopigments have been prepared by citrate-precursor method.
• XRD peaks and FT-IR bands confirmed pure spinel structure for the whole samples.
• HRSEM revealed the porous nature of the samples with flower-like morphology.
• The blue to greenish-grey color arises from Co3+ content.
• ZnCoxAl2 − xO4 nanopigments can be used as a yellow-orange nanophosphor for LED.

In the present work, ZnCoxAl2 − xO4 (x = 0.00–1.50) nanosized pigments were synthesized for the first time by citrate-precursor autocombustion method and heat treatment at 900 °C. In this new nanopigment system the vacancies participate in the spinel structure since the divalent cobalt ions substitute the trivalent Al ions. Structural, microstructural and optical properties were investigated using XRD, FTIR, TEM, HRSEM, XRF, and PL techniques. XRD and FTIR spectra proved the formation of a pure cubic spinel phase. Size of the synthesized nano-crystals ranges from 15 to 60 nm, which is further confirmed with TEM micrographs. HRSEM confirms the microporous nature with flower-like morphology of the prepared nanopigments. Cation distribution has been suggested for the whole samples that matches quite well with XRD and IR experimental data. PL results show that the ZnCoxAl2 − xO4 pigments have good potential for use as a yellow-orange phosphor for displays and/or white light-emitting diodes.

HRSEM of nanopigments at different magnifications and for ZnCoxAl2 − xO4 (0.00 ≤ x ≤ 1.50) samples. Circles in top two images show the flower morphology and that in the bottom image illustrates the porous nature of the samples powder.Figure optionsDownload as PowerPoint slide