“…Other Mg 2+ ions (∼¼) enter calcium sites with a coordination number 8 and have a smaller ionic radius (0.89 Å) than Ca 2+ ions (1.34 Å). As a result, the unit cell volume should decrease, which is confirmed by the experiment and agrees with the literature data [ 30 ]. Fig.…”
“…Other Mg 2+ ions (∼¼) enter calcium sites with a coordination number 8 and have a smaller ionic radius (0.89 Å) than Ca 2+ ions (1.34 Å). As a result, the unit cell volume should decrease, which is confirmed by the experiment and agrees with the literature data [ 30 ]. Fig.…”
“…After making a pellet, it was sintered at 1200 °C for 12 h (total programming time) and furnace-cooled to room temperature. The presence of a minor peak of TiO 2 in a pure CCTO sample with sintering at 1200 °C for 8 h was also reported by Hu et al [10]; thus this sintering temperature was preferred. However, thermogravimetric and dilatometry testing could provide more relevant information about the calcination and sintering temperature, but this was not possible due to limitation of instruments.…”
In order to produce an ultra-high dielectric constant and low loss factor in a polycrystalline material of Sr +2-modified (concentration 15%) CaCu 3 Ti 4 O 12 (i.e., Ca 0.85 Sr 0.15 Cu 3 Ti 4 O 12 , abbreviated as CSCTO-15) was prepared using a cost-effective solid-state reaction technique. Structural analysis using Rietveld refinement of the X-ray diffraction data has confirmed that the sample crystallizes in a cubic system with space group symmetry of Im3. Morphological/microstructural analysis of the natural surface of a pellet shows dense grain growth, with clearly visible grain boundaries. The dielectric relaxation mechanism of CSCTO-15 has been revealed by the detailed study of frequency-and temperature-dependent dielectric parameters (ε r and tan δ). Analysis of the frequency and temperature dependence of impedance and related parameters, collected by a complex impedance spectroscopic technique, has provided and estimated the contributions of grain, grain boundaries and electrode in the electrical process in the material. The activation energy at high temperatures has been calculated from the temperature-dependent ac conductivity plots at selected frequencies.
“…Perovskite structure is one of the main structural properties of piezoelectric materials. Perovskite materials, e.g., CaCu 3 Ti 4 O 12 (CCTO), have been explored greatly as electroceramics owing to their “giant dielectric response” [4,5,6]. Highly dielectric materials are generally suitable for capacitive type sensor devices and this capacity is also proportionally related to the capacitance, which is increased significantly with relative humidity [3].…”
Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E′: 0.225) and glass transition temperature (Tg: −58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials.
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