R. Nouwen

Use of thermogravimetric analysis-Fourier transform infrared spectroscopy in the study of the reaction mechanism of the preparation of Pb(Zr, Ti)O3 by the sol-gel method

Abstract The thermal decomposition of a sol-gel precursor of Pb(Zr, Ti)O 3 is studied by thermogravimetric analysis-Fourier transform infrared spectroscopy in argon and in air. It is found that in an inert atmosphere the presence of residual carbon inhibits the formation of the perovskite structure. In air the evolution of volatile compounds such as alcohols, esters, ethers and CO 2 at temperatures above 300°C indicate that polymerization is still going on during the thermal decomposition of the precursor.

Nucleation and orientation of sol-gel PZT-films on Pt electrodes

Abstract The nucleation and preferential orientation of Lead Zirconate-Titanate (PZT) films deposited by sol-gel spin-coating on Pt bottom electrodes is discussed. The crucial role of the Ti adhesion layer is highlighted. A qualitative crystallization model is presented which can explain the nucleation behavior of PZT-films with different Zr/Ti-ratios on different electrode structures as well as the preferential orientation of the PZT-film.

The use of Hi-Res TGA, TG-FTIR, HT-DRIFT and HT-XRD in the study of the decomposition of La2(C2O4)3·10H2O

Using a combination of various techniques, more intermediate products could be detected during the thermal decomposition of La2(C2O4)3·10H2O than from conventional TGA measurements. In this way a more complete and detailed decomposition mechanism is proposed. Direct identification of the intermediate phases with HT-DRIFT revealed the presence of another oxycarbonate La2O(CO3)2, while with Hi-Res TGA a thermally unstable intermediate La2(CO3)3 was detected. All this information is consistent with the data obtained from TG-FTIR spectroscopic measurements.

The use of TGA-MS, TGA-FTIR, HT-XRD and HT-DRIFT for the preparation and characterization of PbTiO3 and BaTiO3

Abstract Our research is focused on the preparation and characterization of promising multimetal oxide ceramic materials, such as superconducting cuprates and ferroelectric materials. Results of the sol–gel synthesis of two compounds are discussed: PbTiO 3 (PTO) and BaTiO 3 (BTO). These are important products in the study of ferroelectric materials, with interesting applications as non-volatile ferroelectric random access memories (NVFRAMs), such as PbZr 1− x Ti x O 3 (PZT) and BTO-stabilized PbZn 1/3 Nb 2/3 O 3 (PZN). The aim of this presentation is to show how the combination of TGA-evolved gas analysis (TGA-EGA) (i.e. mass spectrometry (MS) and Fourier transform infrared spectroscopy (FTIR) on-line coupled to TGA) gives important, but not sufficient, information for a complete identification of the intermediates that are formed during thermal decomposition. By using TGA-EGA, these intermediates can only be determined indirectly by calculation from the weight losses or by the identification of the evolved gasses. Direct information about the intermediates and the final decomposition products can be obtained by in situ high-temperature-X-ray diffraction (HT-XRD) and high-temperature-diffuse reflectance FTIR (HT-DRIFT) measurements during heat treatment.

Study of different chemical methods to prepare ceramic high-temperature superconductors

The preparation of precursors of bulk , and materials by coprecipitation-filtration of hydroxides or oxalates and sol-gel techniques is presented. Their properties are compared with those of products prepared by the conventional solid-state reaction method by means of TGA, FTIR, XRD, SEM, EDX and resistivity measurements.

Absorption-Reflection Infrared Spectroscopy Studies of Sol-Gel Prepared Ferroelectric Pb(Zr,Ti)O3 Thin Films on Pt Electrodes

Although the sol-gel method is ideally suited for the preparation of ferroelectric PZT thin films, poor reproducibility and the need to lower crystallization temperatures remain an issue. To address these problems, we have studied the mechanism of thin film formation using absorption-reflection infrared spectroscopy for a novel and less harmful precursor solution system based on butoxyethanol. By recording in situ infrared spectra we were able to monitor hydrolysis, condensation, decomposition and crystallization phenomena versus temperature. We speculate that the lower reactivity of butoxyethanol is responsible for the higher quality of Ti rich PZT based ferroelectric capacitors prepared by a butoxyethanol precursor solution compared with the more widely used methoxyethanol one. Finally, we observed that films decomposition kinetics is faster as compared to bulk samples and depends on film thickness and electrode layer.

Preparation and characterization of coprecipitates and mechanical mixtures of calcium-strontium oxalates using XRD, SEM-EDX and TG

Abstract In view of the study of the chemistry of the oxalate coprecipitation process for preparing BiSrCaCuO superconductors, the characteristics of oxalates of calcium and strontium in the Ca(NO 3 ) 2 –Sr(NO 3 ) 2 –HNO 3 –H 2 O–(NH 4 ) 2 C 2 O 4 system are investigated. Based on XRD, SEM and TG a comparison between the crystal structure, morphology and thermal decomposition behavior of coprecipitated and physically mixed calcium and strontium oxalates with the same Ca/Sr stoichiometry is made. It is shown that the coprecipitated powders form homogeneous solid solutions of which the crystal structure, morphology and thermal behaviour depend on the Ca/Sr stoichiometry.

Sol–gel synthesis and properties of YBa2(Cu1−xMx)4Oy (M=Co, Ni) and effects of additional replacement of yttrium by calcium

Abstract In this work the influence of replacing Cu by Ni or Co on the structural and superconducting properties of YBa 2 Cu 4 O 8 is studied by means of XRD, TGA, SEM, EDX and resistivity measurements. The samples are prepared by the acetate–tartrate sol–gel method, which has proved to be very appropriate for the synthesis of Y-124 at 1 atm with even very small amounts of dopants. It is demonstrated that the transition temperature drastically decreases upon Co or Ni substitution, and that superconductivity is lost at 3% Ni and 6% Co doping. XRD measurements show that Ni and Co produce different structural effects to the orthorhombic YBa 2 Cu 4 O 8 phase, possibly because they are introduced in different copper positions. Interesting results are obtained by additional substitution of Y by Ca in the Co- and Ni-doped samples: It is shown that the superconducting properties are enhanced in the samples with less than 3% Ni or 6% Co, and that superconductivity is even recovered in samples with more than 3% Ni or 6% Co.

Thermal treatment of a modified alkoxide gel precursor for the preparation of the YBa2Cu4O8 superconductor

A precursor of Y-Ba-Cu oxides was prepared by a modified alkoxide sol-gel method and its thermal decomposition in air was studied by on-line coupled TG-FTIR and High Resolution Thermogravimetric measurements. A continuous more or less stepwise weight loss was observed between room temperature and 600°C at which all organic compounds had evolved and were progressively oxidized as the temperature increased leaving only Y and Cu oxides and bariumcarbonate. Between 700 and 800°C a final weight loss was observed due to the decomposition of bariumcarbonate into oxide.

Thermal treatment of a Y-123 precursor prepared using the hydroxide co-precipitation method

Abstract A Y-123 precursor has been obtained using the hydroxide co-precipitation method. The influences of the calcination time and temperature (with and without sintering and annealing) on the formation of the superconducting phase, YBa 2 Cu 3 O 7− δ , are examined using XRD and T c measurements. A comparison between the co-precipitated hydroxide precursor and the conventional dry precursor, obtained by mixing oxides and carbonates, is made. It shows that thermal treatment of the hydroxide precursor at 750°C already gives a superconductor, while the oxide–carbonate precursor is only superconducting after thermal treatment at 850°C.