Chalcogenide materials such as GeTe, Sb2Te3, Ge2Sb2Te5, compounds of sulfur, selenium, and tellurium, are characterized by a rapid and reversible phase transition. They have emerged as versatile candidates for advanced electronic and computing applications due to their unique optical and electrical properties. The potential of single-layer, multi-layer, and superlattice chalcogenides as the active materials in non-volatile memory (NVM) and artificial intelligence (AI) devices is shown in this review. Single-layer chalcogenides often offer exceptional scalability, fast speed, and nonvolatility, enabling them usable for NVM and synaptic devices. Multi-layer chalcogenides with stacked structures exhibit unique properties different from single-layer chalcogenides, allowing high performance such as low power and multilevel storage. Superlattice chalcogenides with alternating chalcogenide layers enable ultra-low power consumption of devices, in which only few of atom moves for the operation of devices. This review also gives some related research details. A comprehensive understanding of these studies provides insights into the design and application of chalcogenide-based devices, offering pathways for future research and innovation in memory and AI hardware.

The potassium sodium niobate (KxNa1−x)NbO3 (KNN) family with the perovskite structure is a technologically important lead-free piezoelectric material. This paper reviews the ferroelectric and structural phase transitions of KNN and related materials. The nature of end members, the physical properties, and phase transitions of simple alkali niobate materials MNbO3 (M=Li, Na, K, Rb, and Cs) are reviewed. The binary solid solution's phase diagram, KNN, is introduced concerning the morphotropic phase boundary (MPB). To understand the phase transitions near the MPB composition, the temperature dependences of lattice dynamical properties of KNN single crystals on optical modes and acoustic modes are reviewed by Raman and Brillouin scattering studies, respectively. Physical properties and phase transitions of KNN-based solid solutions were also reviewed.

Tactile technology is becoming increasingly important due to robotics applications and the use of the metaverse. However, there is few research on tactile technologies that can provide information on two-point discrimination thresholds at the human sensory level, and practical application has not progressed. This is due to the fact that the devices are complex and cannot be compactly mounted in key locations such as fingertips. This research aims to develop thin, flexible piezoelectric resin devices and put them into practical use. Here, it is important to miniaturize the drive circuits that drive such piezoelectric devices, so we developed a drive system that uses a piezoelectric driver IC that utilizes serial communication, and is capable of generating a wide range of tactile sensations, including multi-tone gradations.