However, the origin of the two states differs. Superparamagnetism reflects the balance of the anisotropy and thermal energies of small clusters leading to a temperature-dependent large susceptibility. But, as we will show in this paper, superparaelectricity reflects the incomplete ferroic long-range order in nanoclusters. While a ferroelectric state is an assembly of long-range-ordered polar structures yielding a sizable remnant polarization (P r) and a hysteric polarization response (P) to an external electric field (E) (Figure 1a,d), the superparaelectric state consists of short-range-ordered nanometer polar clusters (NPCs), thereby displaying a P r ∼ 0 and a nonhysterical P-E curve (Figure 1b,e). Both states show large dielectric constants ε r due to the strong capacitive responses of their polar regions. For a given material, its ferroelectric state shows a higher initial ε r than that of the superparaelectric state. However, the latter can sustain its large ε r in a broad field or frequency range (Figure 1h,k), as compared to a decreasing ε r of the former with an increasing field or frequency (Figure 1g,j). Such characteristics are ideal for high k dielectric and energy storage applications (Figure 1d-f). [6,7] A superparaelectric state will develop in a ferroelectric material when its grain/cluster size R falls in R cr < R < R c , R c is the correlation length of polarization fluctuations, R cr is the paraelectric limit (Figure 1b). [8] Paraelectric clusters of R < R cr Analogous to the superparamagnetic state, a superparaelectric state is both scientifically intriguing and technologically important. In this state, a ferroelectric material shows a high dielectric constant and a nonhysteretic response to an external electric field, ideal for high k and capacitive energy storage applications. Despite many explorative studies, only circumstantial evidences for its existence are reported. Here, the existence of a superparaelectric state is directly proven in engineered nanocrystalline perovskite films of (Ba 0.95 , Sr 0.05)(Zr 0.2 ,Ti 0.8)O 3 , which are grown on Si at a low temperature and consist of many well-dispersed, nanometer-size polar clusters. These nanoparticles are locally polar, and only lose their shortrange order after being heated up to ≈460 °C, above which they become paraelectrics. Furthermore, they collectively present a pseudo-linear, frequency-insensitive dielectric response, which is characterized by a closeto-zero remnant polarization and a large relative dielectric constant (≈65-70). Capacitors based on these superparaelectric films display high recyclable energy densities (≈100 J cm −3) and efficiencies (≈90%) at room temperature, as well as a reliable high field endurance and good frequency (up to ≈15 GHz) and temperature (up to ≈300 °C) stabilities in their dielectric properties.

No abstract

No abstract

No abstract

Enhancing the central frequency ( fc) and bandwidth (BW) and reducing insertion loss (IL) are essential steps in surface acoustic wave (SAW) filter applications in the 5G era. With this in mind, we construct a 32° Y-X LiNbO3(300 nm)/SiO2(300 nm)/poly-Si(1  μm)/Si heterostructure to avoid both acoustic leakage through the waveguide effect and electrical loss through the introduction of a poly-Si layer. By separately modulating the electrode thicknesses of series and parallel resonators, the spurious modes can be mitigated out of the filter passband, preventing them from negatively impacting the filter characteristics. Moreover, to reduce Ohmic loss, an optimized design for an Al/Cu/Ti multilayer electrode is proposed as a replacement for the Cu/Ti electrode resonators built on Al/Cu/Ti electrodes provide a high resonance frequency of 3.76 GHz, a large electromechanical coupling coefficient of 23%, and a maximum quality factor of 1510 (twice that of the Cu/Ti electrodes). Finally, SAW filters with an fc of 3728 MHz and a 3-dB BW of 1052 MHz are implemented, with IL of 0.92 dB. The achieved specifications demonstrates that one-chip SAW filter is expected to become n77 band filtering solution.