On the sol–gel synthesis and thermal, structural, and magnetic studies of transition metal (Ni, Co, Mn) containing ZnO powders

Abstract

Transition metal containing ZnO powders (Zn 1−x M x O, 0 x 0.30; M = Ni, Mn, Co) have been synthesized by a sol-gel process using zinc acetate dihydrate, respective acetate and oxalic acid as precursors with ethanol as a solvent. The process essentially involves gel formation, drying at 80 • C for 24 h to provide the oxalate, and calcination at 500 • C for 2 h to undergo an exothermic reaction and yield Zn 1−x M x O powder. Their XRD patterns correspond to a wurtzite hcp structure similar to that of pure ZnO, but with the lattice parameters varying slightly with type and extent of doping. It is shown that the dissolution of nickel and cobalt in ZnO is less than 10 at.%, whereas that of manganese lies between 10 and 15 at.%. Other phases that emerge include NiO (hexagonal, a = 2.954 Å, c = 7.236 Å), ZnCo 2 O 4 (cubic, a = 8.094 Å) and ZnMnO 3 (cubic, a = 8.35 Å) in the Ni, Co and Mn containing ZnO systems, respectively. Observations of hysteresis loops both at 10 and 320 K and the nature of ESR spectra provide evidence for the ferromagnetic state in nickel containing ZnO powder. Besides, the deviation occurs in the magnetization versus temperature curves in zero field cooled (ZFC) and field cooled (FC) conditions (blocking temperature T B being 32 K for 5 at.% Ni). The magnetic behaviour of manganese and cobalt doped zinc oxide is, however, different, namely, (i) no hysteresis loops, (ii) decrease in magnetization with increase of Mn or Co content, and (iii) identical M-T curves under ZFC and FC conditions. The inverse susceptibility versus temperature curves of Zn 1−x Mn x O compounds reveal ferrimagnetism with Néel temperature T N of 4 K for x = 0.02, but antiferromagnetism for x = 0.15 and 0.25 with Curie-Weiss temperature of −43 and −30 K, respectively.

Structural Characterization and Magnetic Properties of Undoped and Ti-Doped ZnO Nanoparticles Prepared by Modified Oxalate Route

“…The value of the magnetic moment obtained was 0.1004 emu for 4.2% Tidoped ZnO compared with saturation magnetic moment of about 0.15 /Ti atom at room temperature for 5% Tidoped ZnO [4]. Similar existence of ferromagnetism has been observed earlier in Fe-doped ZnO [29] and Mn-doped ZnO [30].…”

“…Zinc oxide is one of such materials that have received special interest because it has both charge and spin degrees of freedom in a single matrix, which lead to the interplay of functionalities (magnetic and electronic). Also the oxalates from the 3d metals such as zinc are isomorphous in nature, which enables the enhancement of physical properties of oxide semiconductors by doping the precursor in the course of synthesis [2][3][4][5][6]. Many research groups that have worked on doping with transition metals have used zinc oxide as a good host material for realizing wide band-gap dilute magnetic semiconductors.…”

Investigation on the catalytic activity of doped low-percentage oxide catalysts Mn/ZnO obtained from oxalate precursor

“…[1][2][3][4][5]. The use of the slightly soluble ZnC 2 O 4 ·2H 2 O as a precursor for preparing nano-sized pure ZnO and ZnO, doped with transition metals' ions has been growing in the last few years [6][7][8][9][10][11][12][13][14][15][16]. Advantages of the oxalate precursor are its easy synthesis, low temperature of decomposition and the evolution of a large amount of volatile substances (CO, CO 2 , H 2 O), which is prerequisite for the formation of the oxide with high surface area value.…”

“…Another advantage is that the oxalates from the magnesium series (Mg, Mn, Co, Fe, Ni and Zn) are isomorphous. This enables modification of the ZnO physical properties by doping of the precursor in the course of its synthesis [14][15][16]. The latter approach has been widely applied recently to obtain new generation of microelectronic devices and magneto-optic components.…”

Stabilization of Mn(iv) in nanostructured zinc manganese oxide and their facile transformation from nanospheres to nanorods

“…The refined occupancy factors show, 83% of the tetrahedral sites are occupied by Zn while the octahedral sites are occupied partially by Mn (71%) and Zn (17%). It is rare to have Zn occupy octahedral sites (3d 10 electronic configuration) and it is known to occupy tetrahedral sites in most of its compounds. The occupancy of Zn in an octahedral site for a Zn-Mn-O system has been discussed previously by Blasco et.al.…”