Effects of Mg2+ concentration on the structure and optical properties of MgxAl2O3+x:0.88% Cd2+ (0.25 ≤ x ≤ 4.5) nano-powders synthesized via citrate sol-gel

The effects of varying the Eu3+ concentration on the structural and optical properties of Mg1.5Al2O4.5:x% Eu3+ (0 ≤ x ≤ 2) nanophosphors prepared by sol–gel method

“…It can be seen that doping the host with Eu 3+ ions increases and also decreases the diffraction intensity, which suggests the loss and gain of crystalline quality during the growth of Mg 1.5 Al 2 O 4.5 nanocrystals. 10 The crystallite sizes of the Mg 1.5 Al 2 O 4.5 : x % Eu 3+ (0 ≤ x ≤ 2) series were calculated by using the Scherrer’s equation 14…”

“…In all of these studies, 3 –5,8,9 the mole ratio of Mg:Al were fixed or kept constant at 1:2 without any clear motivation. Our previous results 10 in Mg x Al 2 O 3+ x :0.88% Cd 2+ system have showed that the optimum mole ratio of Mg:Al is 1.5:2 for the optimum PL emission intensity. With this in mind, note that the Mg 1.5 Al 2 O 4.5 : x % Eu 3+ system has never been reported in the literature to date.…”

Effects of Varying Alx Moles on the Structure and Luminescence Properties of ZnAlxO1.5x + 1:0.1% Tb3+ Nano Phosphor Prepared using Citrate sol-gel Method

“…The ZnAl2O4 normally crystallizes in the cubic crystal structures of the 3 ̅ space group, where Zn and Al respectively occupies the tetrahedral (Td) and octahedral (Oh) sites in the crystal matrix while oxygen atoms occupies the Wyckoff 32e position located at (u, u, u), where u ≈ 0.25 [1,16,17]. The positioning of the atoms or the structural configuration of the ZnAl2O4 depends on synthesis parameter such as the temperature [18,19] or concentration of the constituent elements [9,15,20]. These can lead in the crystallisation of metal ion in the normal (ZnAl2O4) configuration as described above (where Zn occupies Td and Al occupies Oh sites) or in an inversion (Al[ZnAl]2O4) configuration where the Td is now fully occupied by Al ion and the Oh sites is half-sheared by Al and Zn ions.…”

“…This is because of their band gap located directly at the Г point which was determined theoretically and experimentally to be around few electron volts (eV) [12][13][14]. The MO denoted by the AB2O4 formula are usually referred to as spinel family group, which contains around 120 compound members with ZnAl2O4 (known as zinc aluminate or gahnite) being one of the prominent species in the PL field [1,15]. The ZnAl2O4 normally crystallizes in the cubic crystal structures of the 3 ̅ space group, where Zn and Al respectively occupies the tetrahedral (Td) and octahedral (Oh) sites in the crystal matrix while oxygen atoms occupies the Wyckoff 32e position located at (u, u, u), where u ≈ 0.25 [1,16,17].…”

“…3 (b)), which subsequently affect the lattice constant.The stacked zoomed analysis of the ZnO (101) and ZnAl2O4 (311) displayed inFig. 3 (b)shows that both peaks are shifting towards a lower diffraction angle as x increases up to 1.5 resulting in the expansion of the lattice constant[9,15]. On the ZnAl2O4 phase, this can be caused by the excess Zn 2+…”