Raman scattering investigation of the phase transition in nanocrystalline (Pb, Ca, La)TiO3

Abstract

Nanocrystalline (Pb0.95−xCa0.05Lax)Ti1−x/4O3 (PCLT) powders were prepared by the sol–gel technique. Doping-induced or grain size-induced structure phase transition was investigated by using Raman scattering and x-ray diffraction for the PCLT system. Experimental results show that the soft phonon mode E(TO1) displays a decrease in frequency but an increase in linewidth with increasing concentration of La. A discontinuous behavior of the phonon energy is associated with a phase transition from a ferroelectric tetragonal to a paraelectric cubic phase, and occurs at a morphotropic phase boundary of x≈0.30 for grain sizes being 20 nm. The dependence of Raman phonon modes on the size of particles has been analyzed for nanocrystalline (Pb0.88Ca0.04La0.08)Ti0.98O3 with grain sizes of 10–60 nm and a grain size-induced phase transition is observed for sizes below 14 nm.

Structural transition on Pb1−xSrxTiO3 produced by chemical method

“…In general, the structural effect of the Pb substitution by Sr presents a more analogous behavior than that previously reported in the literature for doped PT and for (Pb 0.95−x Ca 0.05 La x )Ti 1−x/4 O 3 [7,12,20]. It is also important to notice that this tetragonal-cubic transition seems to occur at x values ranging from 0.6 to 0.7.…”

“…Among such important physical properties, the large spontaneous polarization, relatively small dielectric constant (∼200), high Curie temperature T c ∼ 490 • C, and energy band gap of ∼3 eV should be cited [5][6][7][8][9], making them especially suitable for potential use in several applications as, for instance, in memory devices and tunable microwave devices [2].…”

Effect of grain size on the magnetic properties of superparamagnetic Ni0.5Zn0.5Fe2O4 nanoparticles by co-precipitation process

“…7 that we observe a little redshift of the peaks at lower temperatures, which could be called 'softening' very similar to pressure or concentration dependence of the soft mode in other materials. The softening could also be explained by ionic substitution [36].…”

Characterizations of BT Ceramics Synthesized by Modified Solid State Route

“…The SSR route has advantages with respect to the use of relatively low cost raw materials and simple processing steps. Whereas, chemical solution methods are used to produce more homogeneous, finer particle size and low impurity level powders than that produced by the SSR route [15][16][17]. But, chemical solution methods require expensive high purity chemicals and the method is complex.…”