The polycrystalline NaMgPO_(4)ceramic,synthesized via a high-temperature solid-state reaction route,has been characterized by using different experimental procedures.The X-ray powder diffraction confirmed the phase fo...The polycrystalline NaMgPO_(4)ceramic,synthesized via a high-temperature solid-state reaction route,has been characterized by using different experimental procedures.The X-ray powder diffraction confirmed the phase formation of the synthesized com-pound in the orthorhombic phase.It assumed an olivine-type structure made up of corners linked between tetrahedral PO_(4)and octahedral NaO_(6)and MgO_(6)groups.Infrared and Raman spectroscopies confirmed the presence of PO_(4)^(3−)groups.Local structure and chemical bonding between MgO_(6)octahedral and PO_(4)3−tetrahedral groups investigated by diffusion Raman is the feature in the phase transition at T=693 K.The temperature dependences of the realε′and imaginaryε″parts of dielectric permittivity show a distribution of relaxation times.From Nyquist plots,the presence of grain and grain boundary effect in the material is noticed.The impedance spectroscopy measurement showed a non-Debye-type process.From the impedance data,the determined grain resistance reduces with increment of temperature showing negative temperature coefficient of resistance(NTCR)-type nature of the material which also confirmed from conductivity analysis.The temperature dependence ofσdc reveals an Arrhenius-type behavior with two activation energies,0.98 eV in region I and 0.67 eV in region II.Studied sample’s conduction is assured by Na+ions’hopping in tunnels and its mechanism was discussed.展开更多
The complex impedance of the bis(2-amino-6-methylpyridine)tetrachloridozincate compound(C_(6)H_(9)N_(2))_(2)ZnCl_(4) has been investigated in the temperature range 313-403K and in the frequency range 200 Hz-5MHz.The i...The complex impedance of the bis(2-amino-6-methylpyridine)tetrachloridozincate compound(C_(6)H_(9)N_(2))_(2)ZnCl_(4) has been investigated in the temperature range 313-403K and in the frequency range 200 Hz-5MHz.The impedance plots show semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results.The circuits consist of the parallel combination of bulk resistance R_(p) and constant phase elements(CPE).The bulk resistance of the material decreases with rise in temperature.dc conduction activation energies are estimated from Arrhenius plots.The frequency-dependent conductivity data arefitted in the modified power law:σ_(ac)(ω)=σ_(dc)+A_(1)ω^(s1)+A_(2)ω^(s2).Dielectric data were analyzed using complex electrical modulus M^(*) at various temperatures.The modulus plot can be characterized by full width at half height or by β values of Kohlrausch-William-Watts(KWW)function.Activation energy of hopping is almost close to the activation energy of conduction suggesting a hopping transport mechanism.展开更多
文摘The polycrystalline NaMgPO_(4)ceramic,synthesized via a high-temperature solid-state reaction route,has been characterized by using different experimental procedures.The X-ray powder diffraction confirmed the phase formation of the synthesized com-pound in the orthorhombic phase.It assumed an olivine-type structure made up of corners linked between tetrahedral PO_(4)and octahedral NaO_(6)and MgO_(6)groups.Infrared and Raman spectroscopies confirmed the presence of PO_(4)^(3−)groups.Local structure and chemical bonding between MgO_(6)octahedral and PO_(4)3−tetrahedral groups investigated by diffusion Raman is the feature in the phase transition at T=693 K.The temperature dependences of the realε′and imaginaryε″parts of dielectric permittivity show a distribution of relaxation times.From Nyquist plots,the presence of grain and grain boundary effect in the material is noticed.The impedance spectroscopy measurement showed a non-Debye-type process.From the impedance data,the determined grain resistance reduces with increment of temperature showing negative temperature coefficient of resistance(NTCR)-type nature of the material which also confirmed from conductivity analysis.The temperature dependence ofσdc reveals an Arrhenius-type behavior with two activation energies,0.98 eV in region I and 0.67 eV in region II.Studied sample’s conduction is assured by Na+ions’hopping in tunnels and its mechanism was discussed.
文摘The complex impedance of the bis(2-amino-6-methylpyridine)tetrachloridozincate compound(C_(6)H_(9)N_(2))_(2)ZnCl_(4) has been investigated in the temperature range 313-403K and in the frequency range 200 Hz-5MHz.The impedance plots show semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results.The circuits consist of the parallel combination of bulk resistance R_(p) and constant phase elements(CPE).The bulk resistance of the material decreases with rise in temperature.dc conduction activation energies are estimated from Arrhenius plots.The frequency-dependent conductivity data arefitted in the modified power law:σ_(ac)(ω)=σ_(dc)+A_(1)ω^(s1)+A_(2)ω^(s2).Dielectric data were analyzed using complex electrical modulus M^(*) at various temperatures.The modulus plot can be characterized by full width at half height or by β values of Kohlrausch-William-Watts(KWW)function.Activation energy of hopping is almost close to the activation energy of conduction suggesting a hopping transport mechanism.
