钨青铜型Ca_(0.28)Ba_(0.72)Nb_2O_6单晶的正常弛豫铁电相转变研究

Normal-Relaxor Ferroelectric Phase Transition in Ca_(0.28)Ba_(0.72)Nb_2O_6 Single Crystals of Tungsten Bronzes Structure

研究了大块Ca0.28Ba0.72Nb2O6(CBN-28)单晶沿[001]方向的铁电介电性能.结果表明,CBN-28单晶的自发极化、剩余极化和矫顽场分别为35.3μC/cm2,32.2μC/cm2和38.1kV/cm.在室温下频率f=10kHz时,介电常数(εr=195,介电损耗tgδ=0.32.变温的介电谱显示该单晶在252℃附近发生了正常铁电体向弛豫铁电体的转变.低频时在325℃～500℃范围内出现了具有弛豫特征的介电反常.120℃附近有一由氧空位的迁移引起的介电弛豫损耗峰,由此计算得激活能为1.19eV.通过阻抗谱计算,在500℃～560℃范围内的电导激活能为1.33eV.

Large Ca_ 0.28 Ba_ 0.72 Nb_2O_6(CBN-28) single crystals exhibit saturated ferroelectric hysteresis loops under an electric field of 115 kV/cm along the direction. Their spontaneous polarization, remanent polarization and coercive field are 35.3 μC/cm2, 32.2 μC/cm2, and 38.1 kV/cm, respectively. The dielectric constant and dielectric loss tgδ of the crystals are 195 and 0.32 at 10 kHz, respectively. A diffused dielectric anomaly with relaxor characteristic was observed in the range of 325℃～500℃ at low freque...