Propagation of phonons in nanocrystalline ZrO2: Y2O3 ceramics

New results on characterization of highly transparent C-modification Lu2O3 nanocrystalline ceramics: room-temperature tunable CW laser action of Yb3+ ions under LD-pumping and the propagation kinetics of non-equilibrium acoustic phonons

“…3) Using also dependence f ω (q 2 l gb )/(1 − f ω ), which not given here (see, e.g. [16][17][18]21]). …”

“…In continuation of our investigations of the acoustic phonon propagation kinetics in the "cubic" Y 3 Al 5 O 12 , Y 2 O 3 , and ZrO 2 -Y 2 O 3 ceramic-hosts for Ln 3+ lasants [16][17][18], in this work we investigated the transport processes of phonon propagation at liquid helium temperature (2.4-3.8 K) using the heat-pulse technique with the aim to estimate the average thickness of grain-boundary layers (l gb ) in novel highly transparent Lu 2 O 3 nanocrystalline ceramic-host for generating Nd 3+ and Yb 3+ ions (see Table 1). Since the measurement and corresponding analysis were carry out by the same methods as in [16][17][18] Fig. 4.…”

Phonon spectrum of compact ceramics: two‐dimensional ordered model

“…It is shown that the results obtained in these limiting models qualitatively agree and in both cases for certain values of the problem parameters a forbidden bandgap was obtained in the phonon spectrum and the approximate analytical expressions were obtained for its boundaries in the elastic limit. The results given in [5] made it possible to relate a "roll-off" in the grain-size function of the diffusion constant of nanoceramics phonons, which was discovered in the experiments with the propagation of weakly inhomogeneous helium phonons [6,7], with the presence of a gap in the phonon spectrum of these materials. In paper [5] the calculations were performed in a completely degenerate scalar model of a crystal, hence, the question of the influence of mixing vibration modes during scattering was not discussed.…”

Structure and Composition of Ba-W-Ti-O Ceramics Interface Regions Formed at Ultrasonic Vibration

“…This approach is based on the analysis of the weakly nonequilibrium phonon (NP) transport in the specimen studied at helium temperatures when the NP wavelength λ is less than the mean grain size R but comparable to the intergranular interface thickness. The method and the model used as well as the peculiarities of the data processing are detailed in [17,18]. In this work we analyzed the propagation of the flow of weakly nonequilibrium thermal phonons generated by pulse heating of a metal (gold) film deposited on a face of the specimen under study.…”

“…where f ω is the probability of the nonequilibrium phonon passage through the grain boundary [18]; l 0 ≈ 0, 6R is the mean ballistic path of NP in a single grain of size R. Figure 3 presents a set of theoretical curves of f ω /(1− f ω ) as a function of q 2 l gb calculated for different ratios between the acoustic impedances of the grain material, ρ 1 v 1 , and intergranular layer, ρ 2 v 2 ; l gb is the layer thickness, and q 1,2 are the wave vectors of a phonon of frequency ω in the grain material and intergranular layer, respectively:…”