Spontaneous polarization of finely disperse dielectrics with surface donor centers

Electromotive Force in a Layer of Finely Dispersed Spontaneously Polarized Semiconductor

“…Structural transformations and diffusion in randomly oriented powder particles cannot lead to the establishment of a macroscopic electric field with its relatively fast fluctuations maintained for an extended period of time. The fluctuations in G can be related to electron processes in the powder layer that were caused by random thermal motion in powder particles [11]. The fluctuations can be a consequence of breaking the condition for the existence of an electric field in semiconductors with a negative real part of the dielectric permittivity [17].…”

“…Spontaneous polarization in a powder film is known to arise from a phase transition in its electron subsystem [11]. Due to the displacement of free moving electrons in the bulk of a powder particle, the latter acquires a dipole moment.…”

“…The polarization of ceramic, ferroelectric, and semiconductor solids in an alternating electric field results in energy losses, the magnitude of which depends on the charge-carrier concentration, temperature, and frequency of the applied electric field. The fabrication of materials with a negative real part of the dielectric permittivity [7][8][9][10][11] and with negative [12] and low [13] dielectric losses was reported previously.…”

“…Meanwhile, a macroscopic electric field spontaneously arises in the powders, which are not ferroelectric; i.e., the powder spontaneously assumes a nonisotropic state. In investigating this phenomenon, a number of characteristic patterns were identified [11,14,15]. Specifically, a voltage drop G ( V) was established to arise abruptly between metallic electrodes with a thin layer of powder sandwiched between them, and only when the powder was exposed to hydrogen gas.…”

“…The polarization of a bilayer film composed of finely dispersed KMnO 4 and mica, exposed to hydrogen, by a sinusoidal electric field occurs without noticeable energy losses, while the polarization of a KMnO 4 film under the same conditions is accompanied by considerable energy losses. Additionally, following hydrogen chemisorption, the real part of the dielectric permittivity of the KMnO 4 powder becomes negative [10,11].…”