Research

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18 pages, 8640 KiB

Open AccessArticle

Impedance Spectroscopy of Fe and La-Doped BaTiO₃ Ceramics

by Malgorzata Adamczyk-Habrajska, Beata Wodecka-Dus, Tomasz Goryczka and Jolanta Makowska

Crystals 2024, 14(2), 131; https://doi.org/10.3390/cryst14020131 - 27 Jan 2024

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A wide range of the interesting properties of electroceramics Ba_0.996La_0.004Ti_0.999O₃ (BLT4) undoubtedly deserves differentiation and optimization. For this purpose, the corresponding donor oxide dope Fe₂O₃ was introduced in excess quantities into the base [...] Read more.

A wide range of the interesting properties of electroceramics Ba_0.996La_0.004Ti_0.999O₃ (BLT4) undoubtedly deserves differentiation and optimization. For this purpose, the corresponding donor oxide dope Fe₂O₃ was introduced in excess quantities into the base ceramics. In this way, an innovative ceramic material with the general formula of Ba_0.996La_0.004Ti_1−yFe_yO₃ (BLTF), for y = 0.001, 0.002, 0.003, 0.004, has been produced. The crystal structure of BLTF ceramics was investigated using X-ray diffraction. The diffraction peaks in XRD confirm the formation of the tetragonal perovskite phase. The electrical properties of BLTF ceramics have been tested using impedance spectroscopy, in the frequency range of 20 Hz–2 MHz and the temperature range of 20–580 °C. To gain absolute certainty on the consistency of the measured data, the obtained impedance spectra were analyzed using the Kramers–Kronig method. The usage of an equivalent circuit, proposed by the authors, allowed grain and grain boundary resistivity to be obtained. Based on the diagram of the natural logarithm of the mentioned resistivity versus the reciprocal absolute temperature, the activation energies of the conductivity processes have been determined. The values of activation energies indicated that the admixture of iron introduced into the BLT4 ceramics played a crucial role in the conductivity of grains and intergranular borders. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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12 pages, 4692 KiB

Open AccessArticle

Glassy Properties of the Lead-Free Isovalent Relaxor BaZr_0.4Ti_0.6O₃

by Cene Filipič, Giovanna Canu, Raša Pirc and Zdravko Kutnjak

Crystals 2023, 13(9), 1303; https://doi.org/10.3390/cryst13091303 - 25 Aug 2023

Cited by 1 | Viewed by 687

Abstract

Glassy dielectric properties were investigated in lead-free BaZr_0.4Ti_0.6O₃ (BZT40) ceramic samples using dielectric spectroscopy in the frequency range of 0.003 Hz–1 MHz and at temperatures of 10 K < T < 300 K. Measurements of the quasistatic dielectric [...] Read more.

Glassy dielectric properties were investigated in lead-free BaZr_0.4Ti_0.6O₃ (BZT40) ceramic samples using dielectric spectroscopy in the frequency range of 0.003 Hz–1 MHz and at temperatures of 10 K < T < 300 K. Measurements of the quasistatic dielectric polarization in bias electric fields up to ~28 kV/cm suggested that a ferroelectric state could not be induced, in contrast to the case of canonical relaxors such as PMN. The quasistatic dielectric and freezing dynamics results for the above field amplitudes showed that BZT40 effectively behaves as a dipolar glass. The relaxation spectrum was analyzed employing a frequency–temperature plot, which showed that the longest relaxation time obeyed the Vogel–Fulcher relation

τ = τ_{0} e x p [E_{0} / (T - T_{0})]

, with a freezing temperature of 76.7 K. The shortest relaxation time, in contrast, was characterized by a freezing temperature value close to 0 K, implying an Arrhenius-type behavior. The higher value of the polarization and the nonlinear third-order dielectric coefficient

ε_{3}

indicated a shift from a pseudospin glass behavior observed for BaZr_0.5Ti_0.5O₃ (BZT50) toward a classical relaxor ferroelectric state. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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8 pages, 2132 KiB

Open AccessArticle

Tungsten Bronze-Type Ceramics for Temperature-Stable Energy Storage Properties: A Feasibility Study

by Xi Shi and Neamul H. Khansur

Crystals 2023, 13(7), 1073; https://doi.org/10.3390/cryst13071073 - 08 Jul 2023

Cited by 1 | Viewed by 928

Abstract

The temperature-dependent energy storage properties of four tungsten bronze-type ceramics are studied together with an investigation of their structure and temperature-dependent permittivity response, i.e., Ba₆Ti₂Nb₈O₃₀ (BTN), Ba₆Zr₂Nb₈O₃₀ (BZN), Sr [...] Read more.

The temperature-dependent energy storage properties of four tungsten bronze-type ceramics are studied together with an investigation of their structure and temperature-dependent permittivity response, i.e., Ba₆Ti₂Nb₈O₃₀ (BTN), Ba₆Zr₂Nb₈O₃₀ (BZN), Sr₃TiNb₄O₁₅ (STN) and Sr₃ZrNb₄O₁₅ (SZN) ceramics. With different cations at A and B sites, those four ceramics exhibit different crystal structures and show significantly different microstructure features and dielectric responses with changing temperatures. It was observed under SEM that BZN has smaller grains and a more porous structure than BTN. SZN shows the most porous structure among all samples, exhibiting a much lower permittivity response than other samples with no signs of phase transitions from room temperature to 400 °C. Though the energy storage response of those samples is generally quite low, they exhibit good temperature stability together with low dielectric loss. It was suggested that by obtaining a denser structure through chemical modification or other methods, those tungsten bronze ceramics with good temperature stability could be promising as energy storage devices when improved energy storage properties are achieved. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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12 pages, 7536 KiB

Open AccessArticle

Gallium-Modified Zinc Oxide Thin Films Prepared by Chemical Solution Deposition

by Izabela Stojanoska, Brigita Kmet, Hana Uršič and Danjela Kuscer

Crystals 2023, 13(7), 1030; https://doi.org/10.3390/cryst13071030 - 28 Jun 2023

Cited by 1 | Viewed by 813

Abstract

Gallium-doped ZnO (GZO) thin films on glass, which can be used as transparent electrodes, were prepared using a spin coating technique. Thermal analysis and Fourier-transform infrared spectroscopy of the dried precursor solution of Zn acetate and Ga nitrate dissolved in ethanol with diethanolamine [...] Read more.

Gallium-doped ZnO (GZO) thin films on glass, which can be used as transparent electrodes, were prepared using a spin coating technique. Thermal analysis and Fourier-transform infrared spectroscopy of the dried precursor solution of Zn acetate and Ga nitrate dissolved in ethanol with diethanolamine confirmed the decomposition of the organic components upon heating and the formation of ZnO at 450 °C. The thin films fired at 600 °C in oxygen and air, and the films annealed at 400 °C in Ar/H_2, were polycrystalline, 140 nm thick, and exhibited a homogeneous microstructure with 50 nm grains and a smooth surface, as shown by X-ray powder diffraction and scanning electron and atomic force microscopy. The sheet resistance R_s measured using the 4-probe technique showed a change in R_s within 80 days for all samples. The R_s of the GZO thin films annealed in oxygen and air with values of MΩ/sq decreased over time. R_s values of 150 kΩ/sq were obtained for GZO thin films annealed in Ar/H₂, but the R_s increased over time. We suggest that the degradation of R_s is related to the adsorption of water on GZO and that the responses depend on the nature of the defects in the GZO lattice. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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0 pages, 3158 KiB

Open AccessArticle

Investigation of Structural and Electrical Properties of Al₂O₃/Al Composites Prepared by Aerosol Co-Deposition

by Victor Regis, Matej Šadl, Geoff Brennecka, Andraž Bradeško, Urban Tomc and Hana Uršič

Crystals 2023, 13(5), 850; https://doi.org/10.3390/cryst13050850 - 21 May 2023

Cited by 2 | Viewed by 1362

Abstract

As the microelectronic industry develops, components that can perform several different tasks receive increasingly more attention, resulting in multifunctional materials being highly sought after. Al₂O₃ is widely present in electronic applications as a protective coating or as an electrical and [...] Read more.

As the microelectronic industry develops, components that can perform several different tasks receive increasingly more attention, resulting in multifunctional materials being highly sought after. Al₂O₃ is widely present in electronic applications as a protective coating or as an electrical and thermal insulator due to its mechanical and thermal stabilities and chemical inertness. Al₂O₃ is also an important dielectric material, with high resistivity and stable permittivity over a wide range of temperatures and electric fields, but its modest permittivity necessitates large effective areas or extremely thin layers when a large capacitance is desired. Composites consisting of discrete conducting phases within an insulating matrix can produce large capacitance via Maxwell–Wagner polarization. In this work, Al₂O₃/Al composite thick films with different volume ratios of Al were prepared using the aerosol deposition method. A relative dielectric permittivity (ε_r′) of 800 at 1 MHz was achieved at 27 vol% of Al, a sixty-sevenfold enhancement compared to Al₂O₃. On the other hand, dielectric losses, tan(δ), at 1 MHz increased from 0.01 for Al₂O₃ up to 0.58 for the composite with 27 vol% of Al. A finite-element model of the composites was implemented, supporting the nonlinear electrical behavior of the composites as function of vol% of Al. Our results show novel possibilities for the applications of Al₂O₃-based materials in the microelectronic industry, especially for temperature-sensitive applications, for which the integration strengths of aerosol deposition are valuable. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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10 pages, 2911 KiB

Open AccessArticle

Influence of Thermal Treatment on the Cross-Sectional Properties of Aerosol-Deposited Pb(Mg_1/3Nb_2/3)O₃−PbTiO₃ Thick Films

by Katarina Žiberna, Matej Šadl, Aljaž Drnovšek, Goran Dražić, Hana Uršič and Andreja Benčan

Crystals 2023, 13(3), 536; https://doi.org/10.3390/cryst13030536 - 21 Mar 2023

Viewed by 1135

Abstract

The thermal treatment of electromechanically active thick films prepared by aerosol deposition (AD) is a common practice to improve their electrical and electromechanical properties. We report on how post-deposition annealing in air affects the unique cross-sectional microstructure and mechanical properties of 0.9Pb(Mg_1/3 [...] Read more.

The thermal treatment of electromechanically active thick films prepared by aerosol deposition (AD) is a common practice to improve their electrical and electromechanical properties. We report on how post-deposition annealing in air affects the unique cross-sectional microstructure and mechanical properties of 0.9Pb(Mg_1/3Nb_2/3)O₃−0.1PbTiO₃ thick films prepared by AD. Transmission electron microscopy revealed minor but detectable changes, such as pore redistribution and grain growth after annealing at 500 °C. We also showed that the stainless-steel substrate is strongly affected by the annealing. The hardness and Young’s modulus of the films increased after annealing, with both properties being discussed in terms of their distribution over the cross-sections of the films. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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15 pages, 2740 KiB

Open AccessArticle

Influence of Oxygen Vacancies on the Impedance Spectrum of Al₂O₃–Na_0.5K_0.5NbO₃ Composites

by Alexander Martin, Kyle G. Webber and Keni-chi Kakimoto

Crystals 2023, 13(3), 463; https://doi.org/10.3390/cryst13030463 - 08 Mar 2023

Cited by 2 | Viewed by 1218

Abstract

Composites based on ferroelectric Na_0.5K_0.5NbO₃ (NKN) and paraelectric Al₂O₃ were observed using impedance spectroscopy at different temperatures. This allowed for the evaluation of the conduction processes of the bulk and grain boundary, revealing the occurrence [...] Read more.

Composites based on ferroelectric Na_0.5K_0.5NbO₃ (NKN) and paraelectric Al₂O₃ were observed using impedance spectroscopy at different temperatures. This allowed for the evaluation of the conduction processes of the bulk and grain boundary, revealing the occurrence of interdiffusion and changes in the conductive properties. The effective conductivity decreased with the increase in Al₂O₃, which is due to the highly resistive nature of Al₂O₃. Interestingly, the activation energy for the bulk response increased from 0.87 ± 0.06 eV to approximately 1.12 ± 0.03 eV, and the activation energy of the grain boundary decreased from 1.26 ± 0.09 eV to 0.99 ± 0.09 eV. These observations of the activation energy revealed the interdiffusion of Al³⁺ ions, leading to the formation of oxygen vacancies in close vicinity to the grain boundary. As a result, the conduction path for charge carriers shifted to take place predominantly along the grain boundary. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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15 pages, 6142 KiB

Open AccessArticle

Morphology Control of PbZr_xTi_1-xO₃ Crystallites under Alkaline Hydrothermal Conditions

by Marjeta Maček Kržmanc, Zdravko Kutnjak and Matjaž Spreitzer

Crystals 2022, 12(11), 1514; https://doi.org/10.3390/cryst12111514 - 25 Oct 2022

Cited by 1 | Viewed by 1239

Abstract

Outstanding ferroelectric and piezoelectric properties of PbZr_xTi_1-xO₃ (PZT) make nano and sub-micrometer particles of this material interesting for future nanotechnological applications as well as for fundamental studies of ferroelectricity at the nanoscale. In the present work, the prospects [...] Read more.

Outstanding ferroelectric and piezoelectric properties of PbZr_xTi_1-xO₃ (PZT) make nano and sub-micrometer particles of this material interesting for future nanotechnological applications as well as for fundamental studies of ferroelectricity at the nanoscale. In the present work, the prospects of a new hydrothermal approach were explored to control the particle size, aggregation stage, and composition of the PZT with the target composition of Zr/Ti = 60/40 (x = 0.6). Starting with water-soluble Zr-, Ti-, and Pb-precursors, the PZT formation was examined in the broad base (KOH) concentration range. The PZT particle size and composition were governed by the ratio of KOH with respect to Pb and not by the absolute KOH concentration (c_KOH). The incorporation of Zr into the PZT perovskite phase began to decline at KOH:Pb ≤ 1.7 and at KOH:Pb > 20. In the concentration range of 20 ≥ KOH:Pb > 1.5, the PZT particles adopted a cube-like shape, the size of which decreased with a decrease in the KOH:Pb ratio. The smallest (<200 nm) and well-separated PZT particles were obtained at KOH:Pb = 1.7. The prevailing PZT crystal structure at a Zr/Ti composition of around 60/40 was rhombohedral; the tetragonal phase also began to appear in Ti-richer PZT compositions (Zr/Ti ≤ 50/50). The developed understanding established the basis for further tailoring of PZT particle morphologies for application-oriented or fundamental research. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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10 pages, 5344 KiB

Open AccessArticle

Enhanced Microwave Dielectric Properties and Sintering Behaviors of Mg₂SiO₄-Li₂TiO₃-LiF Ceramics by Adding CaTiO₃ for LTCC and GPS Antenna Applications

by Zhijian Wang, Feng Pan, Lanlan Liu, Qifeng Du, Ruitao Tang, Jun Ai, Hong Zhang and Ying Chen

Crystals 2022, 12(4), 512; https://doi.org/10.3390/cryst12040512 - 07 Apr 2022

Cited by 10 | Viewed by 1890

Abstract

Mg₂SiO₄ holds promise for its application in the microwave communication field due to its low dielectric constant and high Q×f value. However, its high negative τ_f and high sintering temperature limit its application in low-temperature co-fired ceramic [...] Read more.

Mg₂SiO₄ holds promise for its application in the microwave communication field due to its low dielectric constant and high Q×f value. However, its high negative τ_f and high sintering temperature limit its application in low-temperature co-fired ceramic (LTCC) devices. In this work, Li₂TiO₃ and CaTiO₃ were introduced to improve the τ_f, and LiF was chosen to decrease the sintering temperature. According to XRD patterns and SEM micrographs, the ceramic systems displayed a complex-phase structure, and the microstructure was densified when CaTiO₃ was added. All of the relative densities, dielectric constants, and Q×f values first increased and then decreased as the sintering temperature increased. The MLLC11.5 ceramics sintered at 800 °C could be obtained with the highest Q×f value of 54,581 GHz (at 8.06 GHz), ε_r of 14.13, and τ_f of + 5.81 ppm/°C. Furthermore, it was proven that the MLLC11.5 powders could be co-fired without any reaction with Ag powders at 800 °C, indicating its potential for LTCC application. The MLLC11.5 composition was used to prepare a GPS antenna and showed good prospects for its application in electronic communications. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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Review

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14 pages, 12870 KiB

Open AccessReview

Magnetic Force Microscopy of Multiferroic Bulk Ceramic Oxides

by Hana Uršič, Matej Šadl, Uroš Prah and Val Fišinger

Crystals 2023, 13(5), 838; https://doi.org/10.3390/cryst13050838 - 19 May 2023

Cited by 1 | Viewed by 1346

Abstract

Bulk multiferroic ceramics have been extensively studied due to their great potential for magneto-electric coupling applications such as low-power and multifunctional nano-electronic devices. In most of these studies the macroscopic magnetic performance was investigated, while the magnetic response on the micro- and nano-scale [...] Read more.

Bulk multiferroic ceramics have been extensively studied due to their great potential for magneto-electric coupling applications such as low-power and multifunctional nano-electronic devices. In most of these studies the macroscopic magnetic performance was investigated, while the magnetic response on the micro- and nano-scale was not examined in detail. Local magnetic phenomena can be studied using magnetic force microscopy (MFM), a technique derived from atomic force microscopy. MFM measures the magnetic force between the magnetised tip and the magnetic sample. It is one of the most used methods to characterise the structure of ferromagnetic domains, because the sample preparation is simple, non-destructive and provides a relatively high-resolution image. In this review paper we focus on the MFM analyses of bulk multiferroic ceramics. The core of the article is divided into four sections: the introduction, the preparation of samples prior to MFM examination, the reviews of MFM analyses performed on bulk multiferroic ceramics with and without external magnetic fields, and finally the conclusions and an outlook for the future. Full article

(This article belongs to the Special Issue Advanced Electronic Ceramics)

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