Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2401.13477

Accurate Determination of the Band-Gap Energy of the Rare-Earth Niobate Series

Alka B. Garg·David Vie·Placida Rodriguez-Hernandez·Alfonso Munoz·Alfredo Segura·Daniel Errandonea
View original source ↗Read source document ↗Export metadata ↓

Abstract

In this work, we report diffuse reflectivity measurements in InNbO4, ScNbO4, YNbO4, and eight different rare-earth niobates. From a comparison with the established values of the band gap of InNbO4 and ScNbO4, we have found that the broadly used Tauc plot analysis leads to erroneous estimates of the band-gap energy of niobates. In contrast, accurate results are obtained considering excitonic contributions using the Elliot-Toyozawa model. We have found that YNbO4 and the rare-earth niobates are wide band-gap materials. The band-gap energy is 3.25 eV for CeNbO4, 4.35 eV for LaNbO4, 4.5 eV for YNbO4, and 4.73 - 4.93 eV for SmNbO4, EuNbO4, GdNbO4, DyNbO4, HoNbO4, and YbNbO4. An explanation for the obtained results will be presented. The fact that the band-gap energy is nearly not affected by the rare-earth substitution from SmNbO4 to YbNbO4 and the circumstance that these are the compounds with the largest band gap are a consequence of the fact that the band structure near the Fermi level originates mainly from Nb 4d and O 2p orbitals. We hypothesize that YNbO4, CeVO4, and LaNbO4 have smaller band gaps because of the contribution from rare-earth atom 4d or 5f states to the states near the Fermi level.

Explore related subjects

cond-mat.mtrl-sci

Keep this discovery

BibTeXRIS

Alka B. Garg, David Vie, Placida Rodriguez-Hernandez, Alfonso Munoz, Alfredo Segura, Daniel Errandonea. 2024-01-24. Accurate Determination of the Band-Gap Energy of the Rare-Earth Niobate Series. https://doi.org/10.1021/acs.jpclett.3c00020

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Measuring chiral phonons

Chiral phonons are quantized vibrations where the atomic motion in a solid breaks improper rotation symmetries. In many cases, chiral phonons possess angular momenta and are therefore selective to circularly polarized light. Both fundamental and applied research efforts on chiral phonons have been gaining increasing attention owing to their importance in a variety of fields including spintronics, spin-selective chemical reactions, thermal transport, quantum information processing and biosensing, where the bi-directional spin-lattice coupling enabled by chiral phonons can be harnessed in new ways, and potentially lead to new functionalities. Thus far, the studies of chiral phonons across diverse materials platforms have evolved largely independently within these fields, but the experimental techniques are often interrelated. In this perspective, we present a detailed description, as well as advantages and disadvantages of the current approaches for experimentally measuring chiral phonons in chiral and achiral materials. We conclude with a discussion of new methods for measuring chiral phonons. Ultimately, this work seeks to offer an experimental guide for systematically investigating the properties of chiral phonons in various materials systems and applications.

cond-mat.mtrl-sci↗
arXiv2026

A model of grain growth in UN integrating molecular dynamics, phase-field modeling, and uncertainty quantification

Grain growth kinetics and grain-boundary (GB) properties in uranium mononitride (UN) are investigated through an integrated multiscale framework combining molecular dynamics (MD), phase-field modeling, and surrogate-assisted uncertainty quantification. MD simulations yield GB energies for 27 symmetric tilt boundaries from 0--2000~K, which are consistent with available DFT values. The average GB energy is nearly temperature-independent below 1000~K and increases at higher temperatures. A mechanistic pore-drag model applied to the only available grain growth dataset for actinide nitrides yields a mobility reduction factor of $s \approx 0.93$--$0.99$, statistically indistinguishable from unity, confirming that pore drag is negligible under the experimental conditions. The intrinsic GB mobility is therefore extracted directly from the effective mobility, yielding $M_0 = 2.05\times10^{-15}$~m$^4$/(J$\cdot$s) and $Q_M = 0.89$~eV. Phase-field simulations conducted from 1500--2000~K confirm normal curvature-driven grain growth, with grain size distributions converging to the Hillert-like form. A surrogate-assisted global sensitivity analysis---combining principal component analysis, Gaussian process regression, and Sobol decomposition---reveals that the mobility prefactor $M_0$ dominates output variance at all times, followed by the activation energy $Q_M$, while the GB energy $\gamma$ contributes minimally. These results establish the first quantitative grain growth framework for UN and identify the reduction of uncertainty in $M_0$ and $Q_M$ as the highest-priority target for future experimental efforts.

cond-mat.mtrl-sci↗
arXiv2026

Silicon Solar Cell Design for >30% Efficiency via Singlet Fission

Singlet fission (SF) materials convert high-energy photons into multiple charge carriers, providing a route to exceed the efficiency limits of single-junction silicon solar cells without many of the complexities of multi-junction tandem designs. Following the first demonstration of an SF-enhanced silicon solar cell in 2025, there is a need to understand how SF materials can be effectively integrated into high-efficiency industrial silicon devices and translated from proof of concept to a manufacturable technology. Using coupled optical and electrical simulations, we assess the efficiency potential of several industrially relevant silicon cell architectures combined with SF materials. Interdigitated back-contact (IBC) cells offer the greatest potential for improvement due to unrestricted front-surface access and can achieve efficiencies exceeding 33%. However, performance is highly sensitive to front-surface passivation quality. Appropriate silicon design, particularly controlled surface doping and fixed interfacial charge, can mitigate recombination losses and relax passivation requirements for ultra-thin exciton-transfer layers.

cond-mat.mtrl-sci↗