E. B. Araújo

Raman study of morphotropic phase boundary in PbZr 1 − x Ti x O 3 at low temperatures

The Raman spectra of

Monoclinic phase ofPbZr0.52Ti0.48O3ceramics: Raman and phenomenological thermodynamic studies

{\mathrm{PbZr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}

The concentration-pressure phase diagram for Zr-rich PbZr1-xTixO3 ceramics

ceramics with titanium concentration varying between

Structure of iron niobophosphate glasses investigated by DTA, infrared and Mössbauer spectroscopy

x=0.40

Effect of substrate characteristics on dielectric properties of PZT thin films obtained from oxide precursors

and 0.60 were measured at 7 K. By observing the concentration-frequency dependence of the vibrational modes, we identified the boundaries among the rhombohedral, monoclinic, and tetragonal ferroelectric phases. The analysis of the spectra was made in the view of group theory analysis making possible the assignment of some modes for the monoclinic phase.

Influence of heat treatment on crystallization of strontium barium niobate (SBN) ferroelectric thin films

This work reports on the first Raman detection of the tetragonal to monoclinic phase transition in PZT ceramics near morphotropic phase boundary at low temperatures. The transition is characterized by changes in the frequency of lattice modes with the temperature. The results presented here confirm the previous one recently reported by Noheda et al. using high-resolution synchrotron X-ray powder diffraction technique and dielectric measurements. The stability of the new phase is discussed within the framework of phenomenological Landau-Devonshire Theory.

Structure and nucleation mechanism of the iron lithium niobium phosphate glasses studied by infrared spectroscopy and DTA

This work reports on systematic high-pressure Raman studies of the PbZr1-xTixO3 (0.02≤x≤0.14) ceramics performed at room temperature. The pressure dependence of the Raman spectra reveals the stable phases of the material under pressure variation. The results allowed us to propose a concentration-pressure phase diagram for the Zr-rich PZT system up to pressures of 5.0 GPa.

Determination of the nucleation rate of 50Li2O--50P2O5:xFe2O3 glass by differential thermal analysis

Activation energies for crystallization of 50 glasses, with x = 0, 5 and 10 mol%, were determined by differential thermal analysis (DTA). The structure was investigated by infrared and M?ssbauer spectroscopy. Samples with x = 5 mol% of show larger activation energy . Absorptions at P-O-P, P=O, and units are presents in these glasses. P=O absorptions disappear at compositions with x = 5 and 10 mol% of , which shows absorption around , attributed to units. According to M?ssbauer results high spin and at distorted octahedral sites are present in samples with x = 5 and 10 mol% of , thus working as a network modifier.

Synthesis of strontium barium niobate ferroelectric thin films by an alternative chemical method

PZT is the most studied perovskite-type ferroelectric material both as bulk ceramic as well as thin films. PZT solid solution ceramics are well known by their excellent piezoelectric, dielectric and pyroelectric properties [1]. For more than one decade the fabrication of PZT films has been reported using techniques such as r.f. sputtering [2, 3], sol-gel [4] and others. Very recently the preparation of PZT thin films from oxide precursors [5] was proposed. This method is a hybrid chemical method for ferroelectric thin film preparation based on a pre-calcination of oxides or carbonates. The method was successfully applied to prepare PZT thin films on fused quartz or Pt/Si substrates. Knowledge of the high electric field dependence of the dielectric permittivity can give important information about ferroelectric characteristics of materials. For ferroelectric thin films it enables one to estimate the range of applications for devices. There are many studies on the subject of the d.c. electric field dependence of the dielectric constant in ferroelectric crystals. Triebwasser [6] explained the nonlinearity of the dielectric constant in BaTiO3 from the theoretical dependence using thermodynamic considerations as being due to space charge fields. Next, the variation of permittivity with electric field in perovskite-like ferroelectrics was treated as being associated with an induced ferroelectric state rather than being directly a property of the domain processes [7]. Uchida and Ikeda [8] measured the electric field bias in lead zirconate titanate Pb(Zr, Ti)O3 ceramics (PZT) and presented a tentative model of polarization, concerning the reversal of 180 ◦

A DTA study of activation energy for crystallization in low silica content calcium aluminosilicate glasses

Strontium barium niobate (SBN) thin films of good quality were deposited on Si and Pt/Si substrates using a polymeric resin containing metallic ions. Using x-ray diffraction, the presence of SBN phase for films annealed at 600 °C and 700 °C for 1 hour was identified on both substrates. Films were also crystallized by rapid thermal annealing (RTA) at different temperatures and for different times, presenting good crystallization. Undesired phases such as SrNb2O6 and BaNb2O6 appear in films deposited on Si and Pt/Si substrates for films crystallized using a conventional furnace. However, using RTA these phases were eliminated for films annealed at 700 °C for 60 and 120 seconds.