Complex Perovskite Solid Solutions Research Articles

Dielectric and piezoelectric properties of bismuth-containing complex perovskite solid solution of Bi1/2Na1/2TiO3−Bi(Mg2/3Nb1/3)O3

New lead-free bismuth-containing complex perovskite solid solution, (1−x)(Bi1/2Na1/2)TiO3−xBi(Mg2/3Nb1/3)O3, were synthesized by conventional solid state reaction method. Effect of Bi(Mg2/3Nb1/3)O3 on crystal structure, dielectric and piezoelectric properties were investigated. The XRD analysis showed that all compositions can form single perovskite phase with rhombohedral symmetry. Addition of small amount of Bi(Mg2/3Nb1/3)O3 improves piezoelectric properties and the optimal piezoelectric properties of d 33 = 94 pC/N and k t = 0.46 were obtained at x = 0.7% and x = 0.9%, respectively. Temperature dependence of dielectric constant e r measurement indicated these compounds were typical relaxor ferroelectric.

Growth and Characterization of Relaxor Ferroelectric Pb(Fe2/3W1/3)O3—PbTiO3 Single Crystals

Single crystals of the complex perovskite solid solution (1-x)Pb(Fe2/3W1/3)O 3 —xPbTiO3 [(1−x)PFW—xPT], with x = 0, 0.07, 0.13, 0.27 and 0.75, have been synthesized by the high temperature solution growth using PbO as flux, and characterized by X-ray diffraction and dielectric measurements. With the increasing amount of PT, the crystal structure at room temperature changes from a pseudo-cubic (x = 0, 0.07 and 0.13) to a tetragonal phase (x ≥ 0.27). The dielectric properties of the crystals exhibit a typical relaxor behaviour for x = 0 to 0.27 with frequency-dependent peak temperature (T m ) satisfying the Vogel-Fulcher law, while the crystals with higher PT-content undergo a first-order transition at the ferroelectric Curie temperature T C .

Room temperature magnetoelectric multiferroism through cation ordering in complexperovskite solid solutions

A strategy for developing ferrimagnetism through B-site cation ordering inthermodynamically stable ferroelectric complex perovskites is described, withthe aim of realizing both a spontaneous polarization and magnetization atroom temperature. Specifically, solid solutions of the complex perovskitesPb(Fe2/3W1/3)O3,Sr(Fe2/3W1/3)O3, andBa(Fe2/3W1/3)O3 withBiFeO3 are considered.Preliminary data on the 0.75Pb(Fe2/3W1/3)O3–0.25BiFeO3 ceramic show promising results.

Predominant factors affecting the dielectric and piezoelectric properties of bismuth-containing complex perovskite solid solution

To study the factors affecting the dielectric and piezoelectric properties of bismuth-containing complex perovskites, the solid solution (1− x)Pb(Mg 1/3Nb 2/3)O 3– xBi(Mg 2/3Nb 1/3)O 3 was prepared by the solid state reaction method and its dielectric and piezoelectric properties were investigated. It is found that (1) at room temperature, the nonlinearity of the DE-loop for Pb(Mg 1/3Nb 2/3)O 3 is completely suppressed at a rather low x (<5%); (2) dielectric constant versus temperature curves deviate from the Curie–Weiss law at a temperature T d much higher than the dielectric constant peak temperature T m and T m− T d decreases considerably with increasing x; and (3) frequency dispersion Δ T m= T m (1 MHz)− T m (10 kHz) increases with increasing x. Possible factors responsible for the variation of the dielectric and piezoelectric properties with x are discussed.

Raman spectroscopy of CaTiO3-based perovskite solid solutions

Perovskite-structured solid solutions intended for use as microwave dielectric resonators were studied by Raman spectroscopy. Two distinct categories were investigated: (i) simple perovskite–simple perovskite solid solutions, that is, CaTiO3–SrTiO3 (CTST), CaTiO3–CaZrO3 (CTCZ), CaTiO3–NdAlO3 (CTNA), and CaTiO3–LaGaO3 (CTLG); and (ii) simple perovskite–complex perovskite solid solutions, such as CaTiO3–SrMg1/3Nb2/3O3 (CTSMN). In the latter category, the influence of A-site ion radius was also addressed by examining 0.5CaTiO3– 0.5LaMg1/2Ti1/2O3 (0.5CT–0.5LMT), 0.5SrTiO3 (ST)–0.5LMT, and 0.5BaTiO3 (BT)–0.5LMT. Raman data from the end members and solid solutions are compared, paying particular attention to F2g and A1g mode bands, often associated with ordering of B-site species.

Temperature dependence of spontaneous polarization in solid solution of Pb(Mg 1/3Ta 2/3)O 3–Pb(Yb 1/2Ta 1/2)O 3 prepared by modified wet–dry combination method

Complex perovskite solid solutions of Pb(Mg x Yb 1− x ) 1/( x+2) Ta ( x+1)/( x+2) O 3 (PMYT) were synthesized by modified wet–dry combination in which coprecipitation process was applied to a part of B-site cations (Mg 2+ and Yb 3+) and their temperature dependence of the spontaneous polarization was investigated. The powder X-ray diffraction analysis revealed that this method could effectively eliminate the compositional fluctuation (fluctuation of average composition of each crystallite) which was shown in the samples prepared by a conventional dry method. Their temperature dependence of spontaneous polarization was abrupt as compared with that for PMYT prepared by a conventional dry method. This is due to the difference of fluctuation of Curie temperature in sample that is attributed to the compositional fluctuation.

Low-temperature property investigation of the lead indium-niobate–lead nickel-niobate solid solution

The complex perovskite solid solution (1−x) Pb(In1/2Nb1/2)O3–(x) Pb(Ni1/3Nb2/3)O3 has been successfully prepared by the Columbite precursor method. The temperature dependencies of the dielectric constant and pyroelectric coefficient were measured between −261 and 200°C. Relaxor ferroelectric behavior has been noticed in all compositions across the solid solution. The room-temperature electrostrictive coefficient, Q33, was 1.83×10−2C2/m4 for x=0.10. No room-temperature piezoelectric activity was detected; however, upon cooling to −261°C the maximum coupling coefficients kp=29%, kt=11%, and k33=31% were observed for the composition x=1.00.

Twinning domain in 67Pb(Mg1/3Nb2/3)O3–33PbTiO3 ferroelectric complex perovskite crystal grown by the Bridgman method

Single crystals of 67Pb(Mg1/3Nb2/3)O3–33PbTiO3 (PMN-PT, PMNT) relaxor-based complex perovskite solid solution grown by Bridgman method have pseudo-cubic symmetry under ambient conditions. Examination by means of polarized light microscopy showed that the microstructure of the crystals was dominated by a large number of coarse twin domains. It was confirmed that the most common composition planes were {110} in addition, {112} planes were also observed. These twins may be associated with the transformation of PMNT complex perovskite from the cubic to tetragonal upon a decrease in temperatures. The morphology of the domain structure may be explained from the theory of martensitic transformation.

On the origin of the large piezoelectric effect in morphotropic phase boundary perovskite single crystals

The high-field behavior of perovskite ferroelectrics close to a morphotropic phase boundary is investigated using the thermodynamic theory of ferroelectrics. For Pb(Zr0.55Ti0.45)O3, a phase transition from the rhombohedral to the tetragonal state is predicted for a critical field of approximately 4 MV m−1 parallel to the 〈001〉 axis. The transition is characterized by a strain of 0.015 parallel to 〈001〉. It is postulated that this transition is the origin of the large field-induced strains observed in single crystals of complex perovskite solid solutions with morphotropic phase boundaries. It is proposed that the transition is diffuse with respect to the applied field due to the inhomogeneity of the critical field arising from the B-site disorder in the complex perovskites. A simple random-field model illustrates the hypothesis.

Perovskite solid solutions in the BaO-CuO-Y 2O 3-Nb 2O 5 system

Freeze dried complex carboxylates are highly reactive precursors for complex perovskite solid solutions in the system BaO-CuO-Y 2O 3-Nb 2O 5 On thermal decomposition of the amorphous precursors the formation of complex crystalline phases begins at 600 °C. In most cases the themodynamically controlled phase composition is reached after a reaction time of two hours at about 900 °C. Beginning from the perovskite compound Ba 2YNbO 6 a partial substitution of Y by Cu or by a combination 2/3 Cu,1/3 Nb leads to extended fields of solid solutions with cubic perovskite structure. Substitution according to Y 0,5xBa 2(Y 1-0,5xCu xNb)O 6+x is limited to x ≤ 0,4. A compound LBa 2Cu 2NbO 8 (x=2), well characterized for L=La, does not exist for L=Y. The composition of solid solutions depends on the preparation conditions. There are some signs for an inhomogeneous distribution of B-cations in the cubic perovskites.

Synthesis of binary complex perovskite solid solution by application of both precursor method and wet-dry combination method

Abstract A binary complex perovskite solid solution, Sr(Cu,Zn) 1 2 W 1 2 O 3 (SCZW), was synthesized using a precursor of (Cu,Zn)WO4 (CZW) prepared by a combination of wet and dry methods. Compositional fluctuations in the resulting material were investigated. The new method includes three steps. The first step is a preparation of an oxide mixture of CuO and ZnO (CZ) by the decomposition of a coprecipitate of Cu2+ and Zn2+ (wet process). The second step is a solid-state reaction between CZ and WO3 (dry process) to form a precursor, CZW. The third step is a solid-state reaction between SrCO3 and CZW to form SCZW. Powder X-ray diffraction analysis revealed that the SCZW was free from the compositional fluctuation which could not be eliminated by application of the precursor method alone.