Molecular Structure and Electrical Properties of Copper Zinc Tin Titanate with Metal as a Substitution

Asfaq Faij^*

Department of Material Science and Nano Material, India

Abstract

This paper conducts in-depth research on the ruthenium-substituted calcium-copper titanates (CCTRO, CaCu3Ti4xRuxO12) crystal structure and dielectric properties. It consisted of three samples of varying stoichiometry: The abbreviations for CaCu3Ti4xRuxO12 with x values of 0, 1, and 4 are CCTO, CCT3RO, and CCRO, respectively. A comprehensive structural analysis of the CCTRO samples was made possible by the Rietveld refinement of the XRPD data. The results show that the crystal structure of the unit cell AA’3B4O12 (CaCu3Ti4xRuxO12) remains cubic regardless of whether Ti4+ or Ru4+ ions are in the B crystallographic position. symmetry. The CaCu3Ti4xRuxO12 crystal lattice contains Ru4+ ions with larger ionic radii than Ti4+ (0.605), as evidenced by slight increases in unit cell parameters, cell volume, and interatomic distances. The structural investigations were confirmed by EDXS elemental mapping, TEM, HRTEM, and ADF/STEM analyses, respectively. To find out how the proportion of Ru atoms in CaCu3Ti4xRuxO12 samples affected their electrical properties, impedance and dielectric measurements were used. According to dielectric measurements, one atom of ruthenium per CaCu3Ti4xRuxO12 unit cell maintains the cubic crystal structure while converting dielectric CCTO into conductive CCT3RO. As indicated by our discoveries, the mix of CCTO and CCT3RO earthenware production is great for settling the issue of weight on capacitor dielectric-cathode interfaces.

Keywords

CCTO • Ruthenium substituted calcium-copper titanate • Dielectrics • Conductors

Introduction

The CaCu3Ti4O12 (CCTO) materials are part of the A-site ordered perovskite family AA’3B4O12. Due to their extremely high dielectric permittivity (up to 105), which is practically constant across a wide temperature (100 and 600 K) and frequency range (kHz–1 MHz), CCTO materials have been the subject of extensive research over the past two decades. Researchers are interested in CCTO ceramics as very promising materials for microwave and microelectronic devices due to these properties [1]. The development of capacitors with worked on capacitive execution for versatile electronic gadgets is worked with by the high dielectric permittivity of CCTO materials. However, it was discovered that the dielectric permittivity decrease may be influenced by the characteristics of the ceramic-electrode interface [2]. The gem structure and electrical properties of CaCu3Ti4O12, which serves as both a metallic cathode and a dielectric material, differ significantly. This results in an energy barrier and stress at the clay terminal point of interaction, both of which lower the dielectric permittivity [3]. Therefore, it is necessary to combine electrodes and dielectric ceramics with comparable crystal structures and unit cell parameters in order to produce capacitors with excellent capacitive performance. Utilizing commercially available materials as an interlayer that closely matches the electrode and dielectric’s lattice parameters can lessen stress at the ceramic-electrode interface [4]. It was discovered that the conductivity of the material increases significantly when Ru4+ ions are incorporated into the CCTO crystal structure. Cubic isostructures can be found in CaCu3Ru4O12 (CCRO) and CaCu3Ti4O12 materials.

Space group depicting the metallic and Pauliparamagnetic nature. The dielectric-electrode interfaces can be less stressed by using the CCRO material as an interface between the CCTO ceramic and metallic electrodes.

Because it has a simple perovskite structure of the type ABO3, an oxide with a cubic perovskite structure has the general chemical formula AA’3B4O12. ABO3 perovskite’s crystal structure is very adaptable, allowing for a wide range of ionic substitutions in the A and B positions. This allows for the creation of novel compounds with novel functional properties. The structural type AA’3B4O12, on the other hand, is more rigid than the parent ABO3. Due to an octahedral tilting distortion of BO6 octahedra, a+a+a+ (Glazer’s nomenclature), the B–O–B angle deviated significantly from 180 degrees, which is typical for the ideal cubic perovskite structure. Three-fourths of the A-site cations have square planar coordination (A’-cation site) as a result of this octahedral distortion, while the remaining one-fourth maintain 12-fold coordination. The ideal perovskite cubic unit cell has parameters that are twice as long as the lattice (V = 2ap•2ap•2ap). Larger particles, such as soluble earth particles or lanthanides, typically engage the crystallographic A position, whereas Cu2+ and Mn3+ particles engage the A’- cation site. The B cation did not completely set in stone the electronic and attractive nature of the materials [5]. The presence of titanium ions in the B position makes it possible for the CaCu3Ti4O12 compounds to have enhanced semiconductor properties in addition to a high dielectric permittivity. Through the substitution of single and co-doped metal ions as well as a variety of preparation methods, the dielectric properties of CCTO ceramics have improved over time. It has been demonstrated that metal ions, either on their own or in combination, maintain a very high dielectric value while significantly reducing the dielectric loss (tg).

CaCu3Ti4xRuxO12, on the other hand, was what we set out to make—a compound that isostructurally resembles CaCu3Ti4O12 but has a much higher conductivity [6]. This compound could be successfully utilized as an interlayer between a metallic electrode and a dielectric ceramic to reduce interlayer stress. Ru4+ particles in the B position fundamentally increment the conductivity of AA’3B4O12 materials, yet because of its significant expense, ruthenium can’t be utilized in business applications [7].

In order to produce inexpensive materials with the desired functional properties that can be used in business, our work aimed to increase the amount of ruthenium in the CaCu3Ti4xRuxO12 crystal structure to the greatest extent possible. CaCu3Ti4xRuxO12 ceramics with x upsides of 0, 1, and 4 were produced using the semi-wet precipitation method. With the assistance of the Rietveld-refined X-ray powder diffraction data, a comprehensive structural analysis was carried out [8]. TEM, HRTEM, and ADF/ STEM analysis with EDXS elemental mapping were carried out in order to verify the structural investigations’ findings. We used impedance spectroscopy and dielectric measurements to find out how the amount of ruthenium in the CaCu3Ti4xRuxO12 crystal structure affects the material’s electrical properties [9].

Methods

CCTRO was produced using the semiwet precipitation method in three distinct stoichiometries: CaCu3Ti4−xRuxO12; The abbreviations for x = 0, 1, and 4 are CCTO, CCT3RO, and CCRO, respectively. Due to its easier homogenization of the starting reagents than the solid-state method, the semiwet precipitation method was chosen for the materials preparation. Ca(CH3COO)2 2.5H2O (99.99%, Aldrich, St. Louis, MO, USA) and Ca(NO3)2 100 percent, Alfa Aesar) were estimated in a normal mix utilizing 20 milliliters of refined water. Ti[OCH(CH3)2]4 (97 percent Aldrich Chemical Company Inc.) was dissolved in 10 mL of acidic water to produce Ti4+. After the steady arrangements were combined into a single entity, a RuO2 (99.9% Aldrich) was dispersed in this arrangement [10]. Using a magnetic stirrer, the prepared dispersion was mixed and evaporated in a silicon oil bath. After being homogenized with an agate mortar and pestle, the dry powder was calcined at 700 °C in stages. The finished powder was milled for 0.5 hours in ethanol in planetary YTZ ball-mil before being fired in the air for twenty hours at 900 °C. The XRD data were recorded at room temperature on a Philips PW 1050 diffractometer using CuK1,2 (= 1.54178) Ni-filtrated radiation in accordance with Rietveld for the structural studies. The diffraction power was estimated from 10 to 130° 2 at a stage size of 0.02° and an including season of 12 s for each step. Using the FullProf computing program in the WinPLOTR environment, the CaCu3Ti4xRuxO12 crystal structure was Rietveld refined [11]. A TCH pseudo-Voigt function was used to describe the shape of the diffraction peak line, and a 6-coefficient polynomial function was used to describe the background. A Titan G2 80-200 equipped with ChemiSTEM technology and a Jeol JEM 210 transmission electron microscope (TEM) were utilized in order to carry out ADF/ STEM with EDXS elemental mapping [12]. The Rietveld refinement was based on the previously reported atomic positions and the calculated unit cell parameters, which were calculated using the program LSUCRI (least squares unit cell refinement with indexing) under working conditions of 20 mA and 40 kV During the quick Fourier change (FFT) examination, the Computerized Micrograph software was used as a guide [13].

Under pressure of approximately 400 MPa, the mixed CCTRO powders were broken down 10 mm in one pass. Each compact theoretically has a density of 62% and a thickness of approximately 3 mm. The green compacts were sintered at temperatures of up to 1050 °C in a Protherm tube furnace with a dwell time of 12 hours and a heating rate of 5°/min [14]. Electrical measurements were taken on the sintered CCTRO pellets. At the instrument’s inner recurrence of 1 kHz, temperature-subordinate capacitance and conductivity were estimated at the Wayne Kerr Widespread Extension B224. All estimations were made in a cooling mode somewhere in the range of 150 and 21.3 °C in an air. A suspension of silver powder and ethyl acetate is applied to both sample bases to improve contact between the silver electrodes and the samples’ surfaces. The impedance estimations were done with a Potentiostat-Galvanostat Standard 273A and a Double Phaslock-in Enhancer 5210 brand. The temperature ranged from 150 °C to room temperature for the purposes of the measurements, which were carried out at frequencies ranging from 0.01 Hz to 100 kHz. The demo version of the computer program Z-View2 was used to mathematically model the experimental data (2.6) [15].

Results and Discussion

The structural improvement of three powders’ XRD data obtained at room temperature: CaCu3Ti4O12 (CCTO), CaCu3Ti3RuO12 (CCT3RO), and CaCu3Ru4O12 (CCRO) were the subjects of the space group’s experiments.

The FullProf figuring program was used to complete the Rietveld investigation. In order to generate the line state of the diffraction maximums, a pseudo-Voigt capability was selected. Refinements were made to the uprooting boundaries, scale factor, top shape boundaries, grid boundaries, and variable fragmentary nuclear directions. The unit cell parameters of the CCTO materials are doubled in all three crystallographic axes (V = 2ap, 2ap,2ap) in comparison to the ideal cubic perovskite lattice (ABO3). The Rietveld refinements were based on the previously reported atomic positions: Oxygen atoms were in the Wyckoff sites 24g (x y 0), Ti atoms were in the 8c position at (0 14 14), and Cu atoms were in the 6b position at (0 12 12). The positional coordinate data from the literature were used as starting points for structural refinement. demonstrates that the calculated and observed structural models agree well. The results back up the powders’ identity as a perovskite oxide with only one phase and no secondary phases.

The equivalent circuit was used to fit the intricate impedance spectra of CCTRO sintered ceramics using the Z-View2 computing program. The equivalent circuit with one capacitor (constant phase element, CPE) and one resistor (R) connected in parallel best describes the impedance spectra of CCTRO materials. The calculated resistance values range from 1 to 150 M, indicating the CCTO material’s good dielectric properties by relatively high resistance values. Sintered ceramics containing ruthenium, on the other hand, accumulate points in the CCT3R and CCRO impedance spectra for higher and middle-frequency values of approximately 0.1 and 0.05, respectively. The impedance spectra of these ceramics can only be described using an equivalent circuit with one resistor (R) and one capacitor (CPE) connected in parallel at extremely low frequency values, between 0.1 and 0.01 Hz. However, the obtained resistivity values for CCTRO materials containing and not containing ruthenium differ by more than eight orders of magnitude in the direct current circuit. This behavior demonstrates the high conductivity of CCT3RO and CCRO ceramics. The electrical conductivity of the investigated ceramics at four distinct frequency points.

Conclusions

In this paper, we in-depth investigated the crystal structure and dielectric properties of three CaCu3Ti4xRuxO12 samples with x values of 0, 1, and 4. The crystal structure’s precise analysis was made possible by Rietveld’s enhancement of the XRD data. The B crystallographic position in the CaCu3Ti4xRuxO12 unit cell remains the same regardless of whether the ions Ti4+ or Ru4+ are present, according to the structural analysis.

group in high flight. The CaCu3Ti4xRuxO12 crystal lattice has Ru4+ ions with larger ionic radii than Ti4+, as shown by slight increases in unit cell parameters, cell volume, and interatomic distances. The outcomes of TEM, HRTEM, and ADF/STEM analyses support the findings of structural investigations by EDXS elemental mapping. The electrical properties of the CaCu3Ti4xRuxO12 materials were investigated using impedance spectroscopy and dielectric measurements. At room temperature, the ruthenium in the CaCu3Ti4O12 structure changes these materials’ electrical properties from dielectric to conductive, according to estimates of electrical obstruction. With just one atom of ruthenium per cell, the materials’ conductive properties can also be significantly improved. Conductivity increases by more than five significant degrees for the recurrence of 100 kHz and nearly eight significant degrees for the recurrence of 100 Hz when ruthenium particles are added.Because they are a low-cost and ideal combination to address the issue of stress on capacitor dielectric-electrode interfaces, our findings regarding CCTO and CCT3RO ceramics encourage their commercial application in the electronic industry.

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