Barbara Malič - Academia.edu (original) (raw)

Papers by Barbara Malič

ipssc.mps.si

Abstract. A new approach to the synthesis of Pb (Mg1/3Nb2/3) O3 (PMN) based materials is presente... more Abstract. A new approach to the synthesis of Pb (Mg1/3Nb2/3) O3 (PMN) based materials is presented. By manipulating the colloidal interactions, the designed self-assembled aggregates are formed, which enable the synthesis of PMN based materials in a single-...

Le Journal de Physique IV, 1998

Journal of the European Ceramic Society, 2002

Powder mixtures of BaTiO3 and LaNi0.6Co0.4O3 have been investigated by heating stage microscopy, ... more Powder mixtures of BaTiO3 and LaNi0.6Co0.4O3 have been investigated by heating stage microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction in order to study the densification behavior and compound formation. By heating microscopy it was demonstrated, that the addition of a few per cent of each material to the other strongly influences the shrinkage of the ceramics.

Ferroelectric thin films based on Pb(Zr0.30Ti0.70)O3 (PZT 30/70) were prepared by Chemical Soluti... more Ferroelectric thin films based on Pb(Zr0.30Ti0.70)O3 (PZT 30/70) were prepared by Chemical Solution Deposition from lead oxide or lead acetate and transition metal alkoxides in 2-methoxyethanol at 400 °C. The choice of the lead-compound determines the composition of the PZT-sols and as a consequence the course of the thermal decomposition. In the case of PbO the local atmosphere within the bulk of the film during heating is more reducing, i.e. the partial pressure of oxygen is lower, than in the case of Pb(OAc)2 based film. Thus, in the former case a continuous layer of Pt-Pb phase is formed at 400 °C, while in Pb(OAc)2 based film only a low amount of Pt-Pb inclusions could be determined by TEM.

The giant electrocaloric (EC) effect is of great importance for application in cooling or heating... more The giant electrocaloric (EC) effect is of great importance for application in cooling or heating devices of new generation, which would be friendlier for environment. Recent predictions of the existence of the giant EC effect in polymeric and inorganic ferroelectric relaxors are based solely on the indirect measurements of the electric polarization and not on a direct measurement of the EC effect itself. Here a method and analysis of direct measurements of the giant EC effect in various soft and solid ferroelectric materials in the form of thick and thin films is presented. The field dependence of the EC effect is shown for PbMg1/3Nb2/3O3 (PMN) ceramics and P(VDF-TrFE) (68/32 mol%) copolymers.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Fine lanthanum zirconate powder was prepared by thermally decomposing a nitrate-alkoxide-based pr... more Fine lanthanum zirconate powder was prepared by thermally decomposing a nitrate-alkoxide-based precursor derived from dehydrated lanthanum nitrate, zirconium n-butoxide and 2-methoxyethanol. Upon heating, the decomposition of the organic groups was promoted by the nitrate groups, yielding a porous powder that crystallized into a pyrochlore phase at 800 °C. The powder that was heat treated at 900 °C for 1 h was composed of friable agglomerates of approximately 60-nm-sized nanoparticles. The ceramics obtained from the powder heat treated at 900 °C and milled for 30 min reached a relative density of 97.9 % after sintering at 1,400 °C for 10 h, which is at least 100 °C lower than the typically reported temperatures for this material.

PbZrO3 powders have been prepared by an alkoxide-based sol–gel route, starting from lead acetate,... more PbZrO3 powders have been prepared by an alkoxide-based sol–gel route, starting from lead acetate, zirconium n-butoxide, and n-butanol as a solvent, and hydrolysed with different amounts of water in neutral and alkaline medium. The local environment of Zr and Pb atoms was pursued from the sol to the dried (150 °C) and heated (400 °C) powders, by extended x-ray absorption fine structure (EXAFS). The analysis of the sol revealed links between Pb and Zr, and even more links between Zr and Zr. The metal neighbourhoods in the dried powders are not influenced by the hydrolysis conditions. Pb-Zr correlations are gradually lost from the sol to the dried and heated powders, while the loss of Zr–Zr correlations is considerably lower.

The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the mos... more The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient,
lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K+Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT).

Modern wireless communication systems are based on microwave technologies. Ferroelectric devices ... more Modern wireless communication systems are based on microwave technologies. Ferroelectric devices with the electric field dependent dielectric properties and low dielectric losses at microwave frequencies are very promising. Capacitance tunability nc, defined as ...

Acta Chimica Slovenica

The objective of this review is to focus on the processing of ceramics based on sodium potassium ... more The objective of this review is to focus on the processing of ceramics based on sodium potassium niobate (K0.5Na0.5NbO3) as promising candidates for lead-free piezoelectrics. In the first part the review addresses the synthesis of the perovskite solid solution as well as the issue of chemical homogeneity for pure and chemically modified K0.5Na0.5NbO3. The second part covers the sintering and

Microscopy and Microanalysis

ipssc.mps.si

Abstract. A new approach to the synthesis of Pb (Mg1/3Nb2/3) O3 (PMN) based materials is presente... more Abstract. A new approach to the synthesis of Pb (Mg1/3Nb2/3) O3 (PMN) based materials is presented. By manipulating the colloidal interactions, the designed self-assembled aggregates are formed, which enable the synthesis of PMN based materials in a single-...

Le Journal de Physique IV, 1998

Journal of the European Ceramic Society, 2002

Powder mixtures of BaTiO3 and LaNi0.6Co0.4O3 have been investigated by heating stage microscopy, ... more Powder mixtures of BaTiO3 and LaNi0.6Co0.4O3 have been investigated by heating stage microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction in order to study the densification behavior and compound formation. By heating microscopy it was demonstrated, that the addition of a few per cent of each material to the other strongly influences the shrinkage of the ceramics.

Ferroelectric thin films based on Pb(Zr0.30Ti0.70)O3 (PZT 30/70) were prepared by Chemical Soluti... more Ferroelectric thin films based on Pb(Zr0.30Ti0.70)O3 (PZT 30/70) were prepared by Chemical Solution Deposition from lead oxide or lead acetate and transition metal alkoxides in 2-methoxyethanol at 400 °C. The choice of the lead-compound determines the composition of the PZT-sols and as a consequence the course of the thermal decomposition. In the case of PbO the local atmosphere within the bulk of the film during heating is more reducing, i.e. the partial pressure of oxygen is lower, than in the case of Pb(OAc)2 based film. Thus, in the former case a continuous layer of Pt-Pb phase is formed at 400 °C, while in Pb(OAc)2 based film only a low amount of Pt-Pb inclusions could be determined by TEM.

The giant electrocaloric (EC) effect is of great importance for application in cooling or heating... more The giant electrocaloric (EC) effect is of great importance for application in cooling or heating devices of new generation, which would be friendlier for environment. Recent predictions of the existence of the giant EC effect in polymeric and inorganic ferroelectric relaxors are based solely on the indirect measurements of the electric polarization and not on a direct measurement of the EC effect itself. Here a method and analysis of direct measurements of the giant EC effect in various soft and solid ferroelectric materials in the form of thick and thin films is presented. The field dependence of the EC effect is shown for PbMg1/3Nb2/3O3 (PMN) ceramics and P(VDF-TrFE) (68/32 mol%) copolymers.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Fine lanthanum zirconate powder was prepared by thermally decomposing a nitrate-alkoxide-based pr... more Fine lanthanum zirconate powder was prepared by thermally decomposing a nitrate-alkoxide-based precursor derived from dehydrated lanthanum nitrate, zirconium n-butoxide and 2-methoxyethanol. Upon heating, the decomposition of the organic groups was promoted by the nitrate groups, yielding a porous powder that crystallized into a pyrochlore phase at 800 °C. The powder that was heat treated at 900 °C for 1 h was composed of friable agglomerates of approximately 60-nm-sized nanoparticles. The ceramics obtained from the powder heat treated at 900 °C and milled for 30 min reached a relative density of 97.9 % after sintering at 1,400 °C for 10 h, which is at least 100 °C lower than the typically reported temperatures for this material.

PbZrO3 powders have been prepared by an alkoxide-based sol–gel route, starting from lead acetate,... more PbZrO3 powders have been prepared by an alkoxide-based sol–gel route, starting from lead acetate, zirconium n-butoxide, and n-butanol as a solvent, and hydrolysed with different amounts of water in neutral and alkaline medium. The local environment of Zr and Pb atoms was pursued from the sol to the dried (150 °C) and heated (400 °C) powders, by extended x-ray absorption fine structure (EXAFS). The analysis of the sol revealed links between Pb and Zr, and even more links between Zr and Zr. The metal neighbourhoods in the dried powders are not influenced by the hydrolysis conditions. Pb-Zr correlations are gradually lost from the sol to the dried and heated powders, while the loss of Zr–Zr correlations is considerably lower.

The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the mos... more The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient,
lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K+Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT).

Modern wireless communication systems are based on microwave technologies. Ferroelectric devices ... more Modern wireless communication systems are based on microwave technologies. Ferroelectric devices with the electric field dependent dielectric properties and low dielectric losses at microwave frequencies are very promising. Capacitance tunability nc, defined as ...

Acta Chimica Slovenica

The objective of this review is to focus on the processing of ceramics based on sodium potassium ... more The objective of this review is to focus on the processing of ceramics based on sodium potassium niobate (K0.5Na0.5NbO3) as promising candidates for lead-free piezoelectrics. In the first part the review addresses the synthesis of the perovskite solid solution as well as the issue of chemical homogeneity for pure and chemically modified K0.5Na0.5NbO3. The second part covers the sintering and

Microscopy and Microanalysis