Ultrafine particles of ZnGa2O4 obtained by solution combustion and complexation methods
Introduction
Zinc gallate – ZnGa2O4 – a blue-emitting phosphor has received much attention due to its potential applications such as a low voltage field emission display (FED), a vacuum fluorescent display (VFD) [1], [2], [3], [4], [5]. It is expected to be one of the new transparent and conductive materials [6]. Also, the thick film sensors based on ZnGa2O4 have excellent gas sensitivity and stability [7].
ZnGa2O4 has a normal spinel structure, like MgAl2O4 (the natural spinel) with a cubic unit cell (Fd-3m symmetry) that contains a well-packed array of 32 oxygen atoms with cations in tetrahedral and octahedral interstices. Zn2+ ions are located in the tetrahedral sites and Ga3+ ions in the octahedral ones [5], [7].
It is well known that the synthetic method used dramatically influences the composition, the structure and, implicitly, the properties of the spinel oxides [8], [9], [10].
ZnGa2O4 has been prepared by a solid state reaction between zinc and gallium oxides [10], [11], [12] by precipitation [4], spray-coprecipitation [6] and sol–gel processes [5], [13], [14], [15], [16]. Hydrothermal synthesis is a promising chemical method for obtaining fine particles, single phase—ZnGa2O4 [17]. The blue-emitting, highly bright phosphor oxide has also been prepared by combustion reaction using glycine as a fuel [4], [18], [19], [20].
Soft chemistry methods, such as solution combustion or complexation are attractive because the spinel oxides obtained as final products are homogeneous, and also of high purity. Sung et al. [16] obtained ZnGa2O4 nanoparticles combining thermolysis of molecular precursor with a sol–gel process. A single molecular precursor Zn[(μ-OiPr)2GaMe2]2 was used to ensure the stoichiometry of the oxide. The first step could be explained as the formation of ZnGa2O4 nuclei with a good stoichiometry by thermolysis of the precursor.
The goal of this research is to obtain ZnGa2O4, as single phase, fine particles, by two different soft chemistry methods: complexation via tartarate synthesis and solution combustion using glycine and urea as fuels.
We have investigated the following systems:2Ga(NO3)3·9H2O:Zn(NO3)2·6H2O:4C4O6H42−2Ga(NO3)3·9H2O:Zn(NO3)2·6H2O:4.5NH2CH2COOH2Ga(NO3)3·9H2O:Zn(NO3)2·6H2O:7CO(NH2)2
because it allowed us to: (i) synthesize the tartarate complex compound containing Ga(III) and Zn(II)—precursor of ZnGa2O4 and to characterize it (IR and UV–vis spectra); (ii) separate the complex compounds from the precursor solutions used in solution combustion processes (glycine-nitrates process GNP and urea-nitrates process) and to characterize them; (iii) characterize ZnGa2O4 obtained by these two methods (XRD spectra, analytic electronic microscopy TEM and EDXR, photoluminescence spectra).
Section snippets
Synthesis of the precursors
All chemicals Ga(NO3)3·9H2O, Zn(NO3)2·6H2O, tartarate acid (C4O6H6), glycine (NH2CH2COOH) and urea (CO(NH2)2) were of reagent quality (Merck).
Polynuclear coordination compounds—precursors
The nature of precursors is very important in the synthesis of the gallate spinel—ZnGa2O4. Sung et al. [16] have used a single molecular precursor to obtain this oxide. Our approach was to try synthesize a tartarate multimetallic complex containing Zn2+ and Ga3+ in a 1:2 ratio, in order to obtain the mixed oxide, directly.
The tartarate polynuclear compound is characterized by the molecular formula:(NH4)2[ZnGa2(C4O6H4)4(OH)2]·4H2O
The IR spectrum of the compound suggests that the tartarate anions
Conclusions
The complexation method using tartarate acid as ligand and the solution combustion process using glycine and urea as fuels were used in order to obtain ultrafine powder of ZnGa2O4.
The following conclusions can be drawn from this study:
- 1.
All the multimetallic complexes are precursors for ZnGa2O4 spinel oxide;
- 2.
A heating treatment of 800 °C/1 h + 1000 °C/1 h is required in order to obtain well crystallized ZnGa2O4 with a size in the 50–250 nm range;
- 3.
The samples of ZnGa2O4 have been characterized from
References (22)
- et al.
Mater. Lett.
(2002) - et al.
Jpn. J. Appl. Phys.
(2008) - et al.
J. Alloy Compd.
(2008) - et al.
Appl. Phys. Lett.
(1994) - et al.
J. Solid State Chem.
(2006) - et al.
J. Am. Ceram. Soc.
(2000) Infrared and Raman Spectra of Inorganic and Coordination Compounds
(1986)- et al.
J. Ceram. Proc. Res.
(2005) - et al.
J. Mater. Res.
(2002) - et al.
Appl. Phys. Lett.
(1993)et al.J. Eur. Ceram. Soc.
(2007)
J. Electrochem. Soc.
Cited by (10)
Rapid annealing-transformed, intense-red-emitting Eu-doped ZnGa<inf>2</inf>O<inf>4</inf> nanoparticles with high colour purity, for very-high-resolution display applications
2019, Materials Research BulletinCitation Excerpt :Fig. 9 shows the room temperature excitation and emission spectra of these samples. With the excitation at 395 nm, a weak emission was observed in the blue and green regions, attributable to self-activation centres in the ZnGa2O4 host and transition between the photo-excited holes and singly ionized oxygen vacancies, respectively [20,45–47]. Sharp and strong emission bands at 579, 590, 615, 652 and 700 nm correspond to 5D0 → 7Fj (j = 0, 1, 2, 3 and 4) transitions, respectively [17,48–51].
Structural, magnetic and catalytic properties of cobalt chromite obtained through precursor method
2015, Materials Research BulletinNanocrystalline indium-based oxides by tartarate precursor route
2014, Ceramics InternationalCitation Excerpt :Transparent mixed oxides have been synthesized through various methods such as the conventional solid state method involving the mechanical mixing of metal oxides followed by calcination at high temperatures (>1000 °C) for long periods varying from 4 hours to 2 days [10,16,17], the co-precipitation method [18], the aqueous/nonaqueous sol–gel procedure [4,12,19,20] and the self-template reaction [21]. As far as we know, there are only few studies regarding the preparation of these oxides by the precursor method (also known as the complexation method) which consists in the thermal decomposition of multimetallic complex compounds [22]. The main goal of this research is the preparation of nanocrystalline Cu2In2O5 and CdIn2O4 by the precursor method through the tartarate precursor route.
Investigation of nanocrystalline zinc chromite obtained by two soft chemical routes
2014, Materials Research BulletinCitation Excerpt :The formation of the precursor as a single molecular compound influences the homogeneity and stoichiometry of the final oxide. There are only few papers in which the precursors of the solution combustion process are isolated [23,29–33]. The nature of the fuel and the fuel to oxidizer ratio are two important parameters of the self-ignition step.
Synthesis of CuGa <inf>2</inf>O <inf>4</inf> nanoparticles by precursor and self-propagating combustion methods
2012, Ceramics InternationalCitation Excerpt :Generally, control over particle size, surface area and crystallinity is indispensable to develop catalytic and photocatalytic properties [6]. The most common synthetic routes for obtaining such oxides are (i) solid-state reactions [2,7–9], (ii) chemical methods including microwave-hydrothermal [6,10,11] and sol–gel synthesis [1,12], and (iii) complexation method [5,13]. The present paper reports on the obtaining of CuGa2O4 by two wet chemical routes: (i) precursor method which means complexation followed by thermal decomposition of the resulting polynuclear complexes and (ii) self-propagating combustion using a glycine-nitrate system.