Luminescence properties of lanthanum oxide, neodymium oxide, samarium oxide and cobalt nitrate doped zinc borate compounds

The compound Zn3B2O6 synthesised in this thesis is monoclinic. The optical properties of zinc borate doped with lanthanum oxide, neodymium oxide, samarium oxide and cobalt nitrate were investigated. The crystal structures of these compounds have been revealed by XRD. A decrease in photoluminescence (PL) intensity was observed when the molar amount of B2O3 in the synthesised compound 3ZnO + B2O3  Zn3B2O6 was increased to 10%, 20% and 30%. The luminescence corresponding to the red light region occurred at 780 nm. The intensities of the peaks at 380 nm increased when the molar amounts of Co(NO3)3 25% and B2O3 100% and 4Zn0 25% were decreased to molar amounts of Co(NO3)3 12.5% and B2O3 100% and 4Zn0 12.5% and then to molar amounts Co(NO3)3 2.5% and B2O3 100% and 4Zn0 2.5%. At 640 nm, all three spectra intersect and the intensities and widths of the peaks at 780 nm and 800 nm increased as the molar amounts of Co(NO3)3 and 4Zn0 were decreased by ¼. When the amount of Nd2O3 was increased from 2.5% to 12.5% mol%, the origin of the blue, green and red emissions was attributed to the recombination of electrons at shallow defect levels with photoexcited holes in the valence band. The ultraviolet emission transitions and the blue, green and red emission band were due to the Nd3+ ion transition. When the amount of La2O3 was increased from 2.5 to 12.5 mol%, excitation bands for La3+ were observed at 405 - 419 - 438 - 465 - 479 - 544 - 554 nm. The emission transitions of La3+ are typical 4f transitions from the excited level to lower levels. Three emission transitions of La3+ were seen at 564 - 599 - 646 nm, with the 599 nm transition being a bright orange-reddish emission. When the amount of Sm2O3 was increased from 2.5% to 12.5% mol%, the excitation spectra for Sm3+ were 390 nm, 527 nm and 561 nm, respectively. The highest transition was found at 390 nm. In order to obtain the emission spectra, four emission transitions due to yellow, orange, orange-red and red emission transitions were detected at wavelengths of 563, 599, 645 and 705 nm. The emission peak power of the transitions increased with the increase in Sm2O3 content from 2.5 mol% to 12.5 mol%. The main distance between Sm3+ ions decreases with increasing Sm2O3 content, which increases the energy transfer between samarium ions.