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Multilayer ceramic capacitors (MLCCs) for electric vehicles require their room temperature capacitance to change ≤ ±15% at −55°C to 200°C. The dielectric constant (ε) of BaTiO3, a dielectric material widely used in MLCCs, drops at >125°C making its application to electric vehicles difficult. Here, we propose KCa2Nb3O10 (KCNO)-layered perovskite as a strong candidate for electric vehicle MLCCs as its ε does not change abruptly with temperature. The effect of sintering temperature on the temperature coefficient of capacitance (TCC) of KCNO is studied. The KCNO powder calcined at 900–1200°C is sintered at 1200°C–1300°C. Microstructure and temperature-dependent ε are determined by the sintering temperature, while the sintered density is related to the difference between the calcining and sintering temperatures. Only the room temperature ε of the samples sintered at 1300°C (except the one calcined at 900°C) varies ≤ ±15% at 25°C–200°C (ε ~250 at room temperature). The sample calcined at 1100°C and sintered at 1300°C has highly elongated grains and the highest activation energy. These factors are responsible for the TCC of the 1300°C sintered KCNO being ≤ ±15% at 25–200°C. [ABSTRACT FROM AUTHOR]

Control of bipolar conduction is essential to improve the high-temperature thermoelectric performance of materials for power generation applications. Recently, Hf(Te1−xSex)2 alloys have gained much attention due to their potential use in thermoelectric power generation. Increasing the Se alloying content significantly increases the band gap while decreasing its carrier concentration. These two factors affect bipolar conduction substantially. In addition, the weighted mobility ratio is estimated from the experimental electronic transport properties of Hf(Te1−xSex)2 alloys (x = 0.0, 0.025, 0.25, 0.5, 1.0) by using the Two-Band model. From the bipolar thermal conductivity also calculated using the Two-Band model, we find that it peaks near x = 0.5. The initial bipolar conductivity increase of x < 0.5 is mostly due to the decrease in the weighted mobility ratio and carrier concentration with increasing x. For x > 0.5, the drop in the bipolar conductivity can be understood with significant band gap enlargement. [ABSTRACT FROM AUTHOR]

Zintl compounds are promising thermoelectric materials for power generation as their electronic and thermal transport properties can be simultaneously engineered with anion/cation alloying. Recently, a peak thermoelectric figure‐of‐merit, zT, of 1.4 was achieved in a (Yb0.9Mg0.1)Cd1.2Mg0.4Zn0.4Sb2 Zintl phase at 700 K. Although the effects of alloying Zn in lattice thermal conductivity had been studied thoroughly, how the Zn alloying affects its electronic transport properties has not yet been fully investigated. This study evaluates how the Zn alloying at Cd sites alters the band parameters of (Yb0.9Mg0.1)Cd1.6−xMg0.4ZnxSb2 (x=0‐0.6) using the Single Parabolic Band model at 700 K. The Zn alloying increased the density‐of‐states effective mass (md*) from 0.87 to 0.97 m0. Among Zn‐alloyed samples, the md* of the x=0.4 sample was the lowest (0.93 m0). The Zn alloying decreased the non‐degenerate mobility (μ0) from 71 to 57 cm2 s−1 V−1. Regardless of Zn alloying content, the μ0 of the Zn‐alloyed samples were similar (∼57 cm2 s−1 V−1). Consequently, the x=0.4 with the highest zT exhibited the lowest weighted mobility (μW). The lowest μW represents the lowest theoretical electronic transport properties among other x. The highest zT at x=0.4 despite the lowest μW was explained with a significant lattice thermal conductivity reduction achieved with Zn alloying with x=0.4, which outweighed the deteriorated electronic transport properties also due to the alloying. [ABSTRACT FROM AUTHOR]

The history of pharmacy in Korea from the era 'Dangun Mythology' to the present day was reviewed briefly with special emphases on the beginning of pharmaceutical education, the introduction of modern pharmaceutical education, the establishment of modern educational institutions, the evolution of a new 6-year pharmaceutical education program, and the separation of drug prescribing and dispensing.