Abstract
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.
Highlights
Metal molybdates form a wide and important class of inorganic materials that have a high application potential in various fields such as scintillator detectors, phosphors and electro-optic applications (Zhang et al 2015; Bavykina et al 2009; Zhou et al 2011; Danevich et al 2014; Belogurov et al 2005; Mikhailik et al 2007; Korzhik et al 2008; Lei and Yan 2008; Shivakumara et al 2015)
All powder XRD patterns were indexed based on the JCPDS file number 04-013-6763 for pure CaMoO4 with tetragonal scheelite-type structure
The scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) measurements were performed on as-prepared samples to characterize their morphology, microstructure, particle size and chemical composition
Summary
Metal molybdates form a wide and important class of inorganic materials that have a high application potential in various fields such as scintillator detectors, phosphors and electro-optic applications (Zhang et al 2015; Bavykina et al 2009; Zhou et al 2011; Danevich et al 2014; Belogurov et al 2005; Mikhailik et al 2007; Korzhik et al 2008; Lei and Yan 2008; Shivakumara et al 2015). Such new dielectric ceramics can be applied as band gap filters, antenna switches and dielectric resonators in mobile and satellite communications, intelligent transport systems, voltage-controlled oscillators and duplexers These systems operating at high frequencies require new materials with relatively low dielectric permittivity (εr), high-quality factor (Qxf) and stable and near-tozero-temperature coefficient of resonant frequency (τf), as well as co-fired with internal metal electrodes, i.e. Al, Ag or Cu (Kim et al 2006; Vidya et al 2013; Xi et al 2014; Choi et al 2007). Low-sintering temperature behaviour, phase composition, microstructure, some dielectric properties and chemical compatibility with metallic aluminium and silver of these nanomaterials were investigated to meet the requirement of microwave devices. C (Groń et al 1995; Krok-Kowalski et al 1997), where kB is the Boltzmann constant, NA is the Avogadro number, μB is the Bohr magneton and C is the molar Curie constant
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