Visible light emission from bulk and nano SrWO4: Possible role of defects in photoluminescence

Nanocrystalline (n-SWO) and microcrystalline (b-SWO) samples of SrWO4 were prepared using polyol and solid state diffusion method, respectively and their crystallite sizes were estimated by powder X-ray diffraction employing Williamson-Hall method. Morphostructural characterization using transmission electron microscopy (TEM) revealed the increased thermal agglomeration and size enhancement in b-SWO particles relative to n-SWO. The photoluminescence emission in both the samples was broad in the range of 400-650 nm. The emission consisted mainly of a narrow peak in the blue region and a broader emission in green region. The fraction of emission in the green region was higher for nanocrystalline SrWO4 than its microcrystalline counterpart. The higher intensity of green emission in nanocrystalline sample is attributed to the large concentration of the oxygen related vacancies.