Dielectric relaxation and conduction behaviors of Aurivillius Na_(0.5)Bi_(4.5)Ti_(4)O_(15) ceramics with Na doping

Aurivillius Na_(0.5)Bi_(4.5)Ti_(4)O_(15) and Bi_(4)Ti_(3)O_(12)compounds were synthesized via solid-state reaction technique.X-ray powder diffraction study confirmed monophasic four-layered Na_(0.5)Bi_(4.5)Ti_(4)O_(15) and three-layered Bi_(4)Ti_(3)O_(12) ceramics.Dielectric relaxation and conduction behaviors of Na-contained Na_(0.5)Bi_(4.5)Ti_(4)O_(15)ceramics were thoroughly investigated in a large scale of temperature of 30-650℃ and frequency of 40 Hz^(-1) MHz.In addition,comparative studies of both the compounds were discussed.Impedance and modulus analyses revealed a single relaxation behavior in Na_(0.5)Bi_(4.5)Ti_(4)O_(15) compound which was originated from the grain’s interior with grain resistance of 2.189×10^(5)Ω and capacitance of 4.268×10^(-10) F at 570℃.While in Bi_(4)Ti_(3)O_(12) ceramic the relaxation was due to the contributions of grain and grain boundaries.Alternating current(AC)conductivity analysis revealed the presence of two different conduction regions in both the compounds.Activation energies for the two different conduction mechanisms,i.e.,in low-temperature region and in high-temperature region were calculated to be~0.23 and~1.27 eV at 1 kHz for Na_(0.5)Bi_(4.5)Ti_(4)O_(15) compound and~0.43 eV and~0.97 eV at 1 kHz for Bi_(4)Ti_(3)O_(12) compound,respectively.The present study of dielectric relaxation and conduction behaviors would be helpful for further investigations of Na_(0.5)Bi_(4.5)Ti_(4)O_(15)-related Aurivillius compounds.