There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...

Low loss dielectric materials for LTCC applications: a review

https://dr.ntu.edu.sg/bitstream/10356/101824/1/A%20comprehensive%20review%20on%20the%20progress%20of%20lead%20zirconate-based%20antiferroelectric%20materials.pdf

A comprehensive review on the progress of lead zirconate-based antiferroelectric materials

A review is presented of the current research and development of shape-memory materials, including shape-memory alloys, shape-memory ceramics and shape-memory polymers. The shape-memory materials exhibit some novel performances, such as sensoring (thermal, stress or field), large-stroke actuation, high damping, adaptive responses, shape memory and superelasticity capability, which can be utilized in various engineering approaches to smart systems. Based on an extensive literature survey, the various shape-memory materials are outlined, with special attention to the recently developed or emerged materials. The basic phenomena in the materials, that is, the stimulus-induced phase transformations which result in the unique performance and govern the remarkable changes in properties of the materials, are systematically lineated. The remaining technical barriers, and the challenges to improve the present materials system and develop a new shape memory materials are discussed.

Shape-memory materials and hybrid composites for smart systems: Part I Shape-memory materials

While NASA explores the power of 3D printing in the development of the next generation space exploration vehicle, a CubeSat Trailblazer was launched in November 2013 that integrated 3D-printed structures with embedded electronics. Space provides a harsh environment necessary to demonstrate the durability of 3D-printed devices with radiation, extreme thermal cycling, and low pressure—all assaulting the structure at the atomic to macroscales. Consequently, devices that are operational in orbit can be relied upon in many terrestrial environments—including many defense and biomedical applications. The 3D-printed CubeSat module (a subsystem occupying approximately 10 % of the total volume offered by the 10 × 10 × 10-cm CubeSat enclosure) has a substrate that fits specifically into the available volume—exploiting 3D printing to provide volumetric efficiency. Based on the best fabrication technology at the time for 3D-printed electronics, stereolithography (SL), a vat photopolymerization technology, was used to fabricate the dielectric structure, while conductive inks were dispensed in channels to provide the electrical interconnect between components. In spite of the structure passing qualification—including temperature cycling, shock and vibration, and outgas testing—the photocurable materials used in SL do not provide the level of durability required for long-term functionality. Moreover, the conductive inks with low-temperature curing capabilities as required by the SL substrate material are widely known to provide suboptimal performance in terms of conductivity. To address these challenges in future 3D-printed electronics, a next generation machine is under development and being referred to as the multi3D system, which denotes the use of multiple technologies to produce 3D, multi-material, multifunctional devices. Based on an extrusion process necessary to replace photocurable polymers with thermoplastics, a material extrusion system based on fused deposition modeling (FDM) technology has been developed that integrates other technologies to compensate for FDM’s deficiencies in surface finish, minimum dimensional feature size, and porosity. Additionally, to minimize the use of conductive inks, a novel thermal embedding technology submerges copper wires into the thermoplastic dielectric structures during FDM process interruptions—providing high performance, robust interconnect, and ground planes—and serendipitously improving the mechanical properties of the structure. This paper compares and contrasts stereolithography used for 3D-printed electronics with the FDM-based system through experimental results and demonstrates an automated FDM-based process for producing features not achievable with FDM alone. In addition to the possibility of using direct write for electronic circuitry, the novel fabrication uses thermoplastics and copper wires that offer a substantial improvement in terms of performance and durability of 3D-printed electronics.

3D Printing multifunctionality: structures with electronics

Antiferroelectric (AFE)‐ferroelectric phase transformations in tin‐modified lead zirconate titanate, i.e., Pb(Zr,Sn,Ti)O3 are reported. A martensitic‐type approach is developed to explain the observed thermal hysteresis and field‐induced transformation behavior. A model is proposed with transformation fields where the forward EF and reverse EA field strengths are related to the transformation barrier to the ferroelectric state, and to the AFE sublattice coupling, respectively. The thermal stability of the AFE state can therefore be determined with respect to the field‐induced transformation behavior. A distinction is made between field‐forced and field‐assisted transformations, which depend on temperature and thermal hysteresis, and which are related to reversible and irreversible field‐induced characteristics. Data are reported for polarizations and strains, and discussed with respect to the proposed thermodynamic model and device applications.

Thermal stability of field-forced and field-assisted antiferroelectric-ferroelectric phase transformations in Pb(Zr,Sn,Ti)O3

An electrode array for neural stimulation is disclosed which has particular applications for use in a retinal prosthesis. The electrode array can be formed as a hermetically-sealed two-part ceramic package which includes an electronic circuit such as a demultiplexer circuit encapsulated therein. A relatively large number (up to 1000 or more) of individually-addressable electrodes are provided on a curved surface of a ceramic base portion the electrode array, while a much smaller number of electrical connections are provided on a ceramic lid of the electrode array. The base and lid can be attached using a metal-to-metal seal formed by laser brazing. Electrical connections to the electrode array can be provided by a flexible ribbon cable which can also be used to secure the electrode array in place.

Electrode array for neural stimulation

We used a regeneratively amplified Ti:sapphire femtosecond laser to create optical birefringence in an isotropic glass medium. Between two crossed polarizers, regions modified by the femtosecond laser show bright transmission with respect to the dark background of the isotropic glass. This observation immediately suggests that these regions possess optical birefringence. The angular dependence of transmission through the laser-modified region is consistent with that of an optically birefringent material. Laser-induced birefringence is demonstrated in different glasses, including fused silica and borosilicate glass. Experimental results indicate that the optical axes of laser-induced birefringence can be controlled by the polarization direction of the femtosecond laser. The amount of laser-induced birefringence depends on the pulse energy level and number of accumulated pulses.

Femtosecond laser-pulse-induced birefringence in optically isotropic glass

Chemically prepared Pb(Zr 0.95 Ti 0.05 )O 3 (PZT 95/5) ceramics were fabricated with a range of different porosity levels, while grain size was held constant, by systematic additions of added organic pore former (Avicel). Use of Avicel in amounts ranging from 0 to 4.0 wt% resulted in fired ceramic densities that ranged from 97.3% to 82.3%. Hydrostatic-pressure-induced ferroelectric (FE) to antiferroelectric (AFE) phase transformations were substantially more diffuse and occurred at lower hydrostatic pressures with increasing porosity. An ∼12 MPa decrease in hydrostatic transformation pressure per volume percent added porosity was observed. The decrease in transformation pressure with decreasing density was quantitatively consistent with the calculated macroscopic stress required to achieve a specific volumetric macrostrain (0.40%). This strain was equivalent to experimentally measured macrostrain for FE-to-AFE transformation. The macroscopic stress levels were calculated using measured bulk modulus values that decreased from 84 to 46 GPa as density decreased from 97.3% to 82.3%. Good agreement between calculated and measured values of FE-to-AFE transformation stress was obtained for ceramics fired at 1275° and 1345°C.

/pdf/pressure-induced-phase-transformation-of-controlled-porosity-3wals4c435.pdf

Pressure-Induced Phase Transformation of Controlled-Porosity Pb(Zr0.95Ti0.05)O3 Ceramics

The temperature dependence of phase stability for tin‐modified lead zirconate titanate solid solution ceramics Pb(0.98)Nb0.02[(Zr1−x, Snx)1−yTiy]1−zO3 (PZST) was investigated by hot‐stage transmission electron microscopy. Compositions studied included, a material that was antiferroelectric (AFE) at room temperature with x=0.42 and y=0.04, and a material that was ferroelectric (FE) at room temperature with x=0.43 and y=0.08 (abbreviated as PZST 42/4/2 and 43/8/2, respectively). PZST 42/4/2 was found to exhibit a sequence of phase transformations on heating of AFE–multicell cubic (MCC)–simple cubic (SC), whereas PZST 43/8/2 had a sequence of FE‐AFE‐MCC‐SC. Previously referred to F spots (i.e., 1/2[111] superlattice spots) were observed in all four phases. The diffraction intensities for the F spots decreased with increasing temperature, and eventually disappeared above 300 °C. Electron diffraction confirmed the presence of the MCC phase which was characterized by the existence of weak 1/2[110] superlattice ...

Pin Yang

Papers

Thermal stability of field-forced and field-assisted antiferroelectric-ferroelectric phase transformations in Pb(Zr,Sn,Ti)O3

Electrode array for neural stimulation

Femtosecond laser-pulse-induced birefringence in optically isotropic glass

Pressure-Induced Phase Transformation of Controlled-Porosity Pb(Zr0.95Ti0.05)O3 Ceramics

Hot‐stage transmission electron microscopy studies of phase transformations in tin‐modified lead zirconate titanate