Abstract
An emerging chalcogenide perovskite, CaZrSe3, holds promise for energy conversion applications given its notable optical and electrical properties. However, knowledge of its thermal properties is extremely important, e.g. for potential thermoelectric applications, and has not been previously reported in detail. In this work, we examine and explain the lattice thermal transport mechanisms in CaZrSe3 using density functional theory and Boltzmann transport calculations. We find the mean relaxation time to be extremely short corroborating an enhanced phonon–phonon scattering that annihilates phonon modes, and lowers thermal conductivity. In addition, strong anharmonicity in the perovskite crystal represented by the Grüneisen parameter predictions, and low phonon number density for the acoustic modes, results in the lattice thermal conductivity to be limited to 1.17 W m−1 K−1. The average phonon mean free path in the bulk CaZrSe3 sample (N → ∞) is 138.1 nm and nanostructuring CaZrSe3 sample to ~10 nm diminishes the thermal conductivity to 0.23 W m−1 K−1. We also find that p-type doping yields higher predictions of thermoelectric figure of merit than n-type doping, and values of ZT ~0.95–1 are found for hole concentrations in the range 1016–1017 cm−3 and temperature between 600 and 700 K.
Highlights
The search for thermoelectric (TE) materials with superior performance in energy conversion, a.k.a. figure of merit (ZT), that can compete against or be considered as alternates to traditional and commercially available materials such as CdTe and CuInSe2,1–3 is still ongoing
During the related materials design and discovery process, a prime importance is placed on the lattice thermal conductance (LTC) that determines the transport of thermal energy through the solid because materials with high LTC yield poor thermoelectric performance i.e., ZT, compared to those with lower LTC
Recent efforts have shown that an emerging chalcogenide perovskite, CaZrSe3, possesses notable optical and electrical properties relevant for energy conversion applications.[19]
Summary
The search for thermoelectric (TE) materials with superior performance in energy conversion, a.k.a. figure of merit (ZT), that can compete against or be considered as alternates to traditional and commercially available materials such as CdTe and CuInSe2,1–3 is still ongoing. Chalcogenide perovskites have surfaced as potential candidates in this space These materials have an ABX3 crystal structure and possess good optical and electronic properties, conducive for promising TE performance.[5,18] Recent efforts have shown that an emerging chalcogenide perovskite, CaZrSe3, possesses notable optical and electrical properties relevant for energy conversion applications.[19] Morelli and Slack[20] recently defined low κL materials as those with κL ≤ 50 W m−1 K−1, while the rest are considered to possess high κL. It was identified that for nonmetallic crystals, fundamental properties that contributed to lower κL included weak interatomic bonded interactions, presence of heavy elements, structural complexity, and large Grüneisen parameters.[21] Here, we examine the phonon thermal transport mechanisms through CaZrSe3 in its orthorhombic distorted perovskite phase. As discussed below in details, strong lattice anharmonicity, a high Debye temperature and short phonon lifetimes contribute to ultralow κL and competitive ZT predictions for potential TE applications
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