Influence of annealing on B-site order and dielectric properties of (0.4)Pb(In[sub 1∕2]Nb[sub 1∕2])O[sub 3]:(0.6)Pb(Mg[sub 1∕3]Nb[sub 2∕3])O[sub 3] relaxor ceramics

Cheuk W. Tai, K. Z. Baba-Kishi
2006 Journal of Applied Physics  
The structural long-range B-site ordered domains and dielectric properties of the as-sintered and postannealed ceramics ͑0.4͒Pb͑In 1/2 Nb 1/2 ͒O 3 : ͑0.6͒Pb͑Mg 1/3 Nb 2/3 ͒O 3 have been characterized. Transmission electron microscopy studies show an increase in the size of the ordered domains following annealing. In the low-field dielectric measurements, the longer the annealing time, the narrower is the diffuse phase transition. A high-temperature dielectric anomaly at low frequency in the
more » ... intered sample significantly weakens following postannealing. The annealed samples retained their exceptionally slim ferroelectric hysteresis loops. Pb-based complex perovskites with a general formula of Pb͑BЈ x BЉ 1−x ͒O 3 are an important class of oxides because of their outstanding dielectric, electromechanical, and electrooptical properties. 1,2 Phase transitions and ferroelectric properties of most Pb-based complex perovskites are influenced by the degree of 1:1 long-range order ͑LRO͒, as exemplified by Pb͑Sc 1/2 Ta 1/2 ͒O 3 ͑PST͒. 3 The influence of order-disorder on the properties of Pb͑BЈ x BЉ 1−x ͒O 3 perovskites have been extensively studied. 4-9 Pb͑Mg 1/3 Nb 2/3 ͒O 3 ͑PMN͒ has a very low degree of LRO, 5 which is controlled by the driving forces originating from differences in size and charge between the B-site cations. Also, the degree of LRO is modified by cation substitutions only. 10 The high-energy electronic configurations of the disordered states are stabilized by the hybridization of Pb 6s and O 2p states. 11 The size of short-range ordered domains is less than 10 nm. 12 Unlike PMN, LRO can be modified by heat treatment in Pb͑In 1/2 Nb 1/2 ͒O 3 ͑PIN͒. Highly ordered PIN is antiferroelectric below the transition temperature, but becomes a relaxor when disordered or incompletely ordered. 13 By mixing an antiferroelectric or relaxor PIN with PMN, a relaxor solid solution ͑x͒PIN: ͑1−x͒PMN is formed. In the as-sintered ceramic form, the dielectric, electromechanical phase transition, ferroelectric hysteresis characteristics, and LRO domain size are composition dependent. 14-17 Here, we report the influence of annealing on the B-site LRO and on the dielectric properties of 0.4PIN:0.6PMN ceramics. 0.4PIN:0.6PMN ceramics were fabricated by the twostep solid state reaction method. 17 Following sintering, two of the samples were annealed at 1050°C for 12 and 36 h and one sample remained in the as-sintered form. Images of the LRO domains were recorded at room temperature using dark-field ͑DF͒ imaging in a JEOL-2011 transmission electron microscope ͑TEM͒ operated at 200 kV. The relative permittivity ͑ r ͒ and loss tangent ͑tan ␦͒ of the silver-coated samples were measured at different frequencies and tempera-tures using an impedance analyzer ͑HP4194A͒ and a computer-controlled oven ͑Delta Design Delta-9023͒. The ferroelectric hysteresis loops of the ceramics were measured at room temperature using a Sawyer-Tower circuit. 18 In ͑0.4͒PIN:͑0.6͒PMN, TEM has revealed superstructure reflections as well as their corresponding domains of LRO, which were not detected in x-ray profiles. DF images of LRO domains in the as-sintered and the two annealed samples were recorded using the superstructure reflection 1/2 1/2 1/2 along a ͗110͘ zone axis ͑Fig. 1͒. In the as-sintered sample ͓Fig. 1͑a͔͒ the size of the ordered domains ranges from 10 to 50 nm across, larger than the domains observed in PMN ͑Ͻ10 nm͒. 12 The domains in the proximity of grain boundaries are larger than those away from grain boundaries. a͒
doi:10.1063/1.2374934 fatcat:ympm2nvl75gejej67ja6cu63em