“…5 and 6). This behaviour well correlates with the band gap values ( E g ) determined by us earlier (Pawlikowska et al 2017), and they are displayed in Fig. 5.…”
Section: Resultssupporting
confidence: 90%
“…A necessary condition for free energy minimalization gives n ≅ N exp(− E V / kT ) for n ≪ N , where N is the number of atoms in the crystal and E V is the energy required to transfer the atom from the bulk of the crystal on its surface (Kittel 1971). Therefore, we expect deep trap levels localized in the energy gap of 4.2 eV (Pawlikowska et al 2017) hindering the electron transport.Fig. 5Electrical conductivity (ln σ ) vs. temperature ( T ) and band energy gap ( E g ) vs. x parameter for Ca 1− x Mn x MoO 4 Fig.…”
Section: Resultsmentioning
confidence: 96%
“…Divalent metal molybdates with relatively large cations such as Ca 2+ , Sr 2+ , Ba 2+ and Pb 2+ (ionic radius above 99 pm) exist in scheelite-type structure (tetragonal symmetry, space group I4 1 /a ; Z = 4) where molybdenum ions adopt tetrahedral coordination, while divalent metal ions represent an eight-coordinated position (Sczancoski et al 2008; Sczancoski et al 2009; Ghosh et al 2015). Generally, metal molybdates are obtained by conventional solid-state reaction method (Pawlikowska et al 2017; Piątkowska and Tomaszewicz 2016; Tomaszewicz et al 2016). However, powders obtained in this way are characterized by large and irregular grains.…”
Section: Introductionmentioning
confidence: 99%
“…Furthermore, molybdenum oxide has a tendency to vaporize at high temperatures and inhomogeneous compounds might be easily formed. These problems can be avoided by applying combustion synthesis, wet chemical route, Pechini and other methods (Pawlikowska et al 2017; Thongtem et al 2010; Marques et al 2010; Gong et al 2006; Chen et al 2006; Piątkowska et al 2017). …”
Scheelite-type Ca1−xMnxMoO4 (x = 0.0, 0.01, 0.05, 0.10 and 0.15) nanomaterials were successfully synthesized via a combustion route. Dielectric studies showed a weak n-type electrical conductivity characteristic for insulators and low relative permittivity (εr < 15) decreasing with increasing Mn2+ content. CaMoO4 and Mn2+-doped nanomaterials are chemically compatible with Al and Ag electrodes and promising for low-temperature co-fired ceramic applications. Magnetic studies showed, at room-temperature diamagnetism for pure CaMoO4, the balance between diamagnetism and paramagnetism for Ca1−xMnxMoO4 (x = 0.01) and paramagnetic behaviour when 0.05 ≤ x ≤ 0.15 as well as the short-range antiferromagnetic interactions growing in strength as Mn2+ content increases. The Landé factor fitting procedure showed a spin-only contribution to the magnetic moment. CaMoO4 matrix unexpectedly revealed the residual paramagnetism at low temperatures derived probably from the molybdenum ions having unpaired 4d electrons as well as a paramagnetic-diamagnetic transition at 70 K.
“…5 and 6). This behaviour well correlates with the band gap values ( E g ) determined by us earlier (Pawlikowska et al 2017), and they are displayed in Fig. 5.…”
Section: Resultssupporting
confidence: 90%
“…A necessary condition for free energy minimalization gives n ≅ N exp(− E V / kT ) for n ≪ N , where N is the number of atoms in the crystal and E V is the energy required to transfer the atom from the bulk of the crystal on its surface (Kittel 1971). Therefore, we expect deep trap levels localized in the energy gap of 4.2 eV (Pawlikowska et al 2017) hindering the electron transport.Fig. 5Electrical conductivity (ln σ ) vs. temperature ( T ) and band energy gap ( E g ) vs. x parameter for Ca 1− x Mn x MoO 4 Fig.…”
Section: Resultsmentioning
confidence: 96%
“…Divalent metal molybdates with relatively large cations such as Ca 2+ , Sr 2+ , Ba 2+ and Pb 2+ (ionic radius above 99 pm) exist in scheelite-type structure (tetragonal symmetry, space group I4 1 /a ; Z = 4) where molybdenum ions adopt tetrahedral coordination, while divalent metal ions represent an eight-coordinated position (Sczancoski et al 2008; Sczancoski et al 2009; Ghosh et al 2015). Generally, metal molybdates are obtained by conventional solid-state reaction method (Pawlikowska et al 2017; Piątkowska and Tomaszewicz 2016; Tomaszewicz et al 2016). However, powders obtained in this way are characterized by large and irregular grains.…”
Section: Introductionmentioning
confidence: 99%
“…Furthermore, molybdenum oxide has a tendency to vaporize at high temperatures and inhomogeneous compounds might be easily formed. These problems can be avoided by applying combustion synthesis, wet chemical route, Pechini and other methods (Pawlikowska et al 2017; Thongtem et al 2010; Marques et al 2010; Gong et al 2006; Chen et al 2006; Piątkowska et al 2017). …”
Scheelite-type Ca1−xMnxMoO4 (x = 0.0, 0.01, 0.05, 0.10 and 0.15) nanomaterials were successfully synthesized via a combustion route. Dielectric studies showed a weak n-type electrical conductivity characteristic for insulators and low relative permittivity (εr < 15) decreasing with increasing Mn2+ content. CaMoO4 and Mn2+-doped nanomaterials are chemically compatible with Al and Ag electrodes and promising for low-temperature co-fired ceramic applications. Magnetic studies showed, at room-temperature diamagnetism for pure CaMoO4, the balance between diamagnetism and paramagnetism for Ca1−xMnxMoO4 (x = 0.01) and paramagnetic behaviour when 0.05 ≤ x ≤ 0.15 as well as the short-range antiferromagnetic interactions growing in strength as Mn2+ content increases. The Landé factor fitting procedure showed a spin-only contribution to the magnetic moment. CaMoO4 matrix unexpectedly revealed the residual paramagnetism at low temperatures derived probably from the molybdenum ions having unpaired 4d electrons as well as a paramagnetic-diamagnetic transition at 70 K.
New inorganic cobalt based blue pigments Mg1‐xCoxWO4 (x = 0.1, 0.2 and 0.3) have been prepared by the solid state reaction and flux added methods. The synthesized samples show intense blue color with very low doping concentration of cobalt. Raising cost and toxicity make a critical need to reduce the consumption of cobalt in the ceramic industry, at the same time trying to improve the efficiency and sustainability of pigments. The present investigation help us minimize the cobalt consumption and cost of production with respect to conventional blue ceramic colorants. Intense blue hue was obtained at relatively low doping concentration of Co2+ (20 mol%) with b* value of −46.97, which is considerably bluer than cobalt aluminate spinel (b* = ‐32.70). UV‐visible absorption properties are strongly related to the coordination environment of the Co2+ ions. Increasing the amount of cobalt induces a change in the local symmetry of MgO6 octahedra witnessed by the change of the metal‐ligand bond distances.The changes are attributed to the larger ionic radius and electronegativity of Co2+ ions compared to the Mg2+ ions in the host lattice.These observations corroborate the important structural distorsions arising from the differences in ionic radii and electronegativity between the dopant and host cations.
A series of Mn 2? -doped and Eu 3? -co-doped calcium molybdato-tungstates, i.e., Ca 1−3x−y Mn y ⌷ x Eu 2x (MoO 4 ) 1−3x (WO 4 ) 3x (0 \ x ≤ 0.2222 when y = 0.0200 and 0 \ y ≤ 0.0667 when x = 0.1667, ⌷ represents vacancy) materials were successfully synthesized via high-temperature annealing. XRD results confirmed the formation of single, tetragonal scheelite-type phases (space group I4 1 /a). A change in both lattice constants (a and c), lattice parameter ratio c/a and progressive deformation of MoO 4 /WO 4 tetrahedra with increasing Eu 3? as well as Mn 2? contents were observed. The melting point of doped materials is lower than the melting point of pure matrix, i.e., CaMoO 4 . New materials exhibit strong absorption in the UV range. They are insulators with the optical direct band gap (E g ) higher than 3.50 eV. The E g values nonlinearly change with increasing dopants concentrations. EPR measurements allowed to establish the nature of magnetic interactions among Mn 2? ions. Additionally, EPR spectra were sensitive on both parameters: Mn 2? and Eu 3? concentration.
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