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  1. Edited by O. V. Yakubovich, Moscow State University (Ed.)
    The NaZr2P3O12 family of materials have shown low and tailorable thermal expansion properties. In this study, SrZr4P6O24 (SrO 4ZrO2 3P2O5), CaZr4P6O24 (CaO 4ZrO2 3P2O5), MgZr4P6O24 (MgO 4ZrO2 3P2O5), NaTi2P3O12 [1 2(Na2O 4TiO2 3P2O5)], NaZr2P3O12 [1 2(Na2O 4ZrO2 3P2O5)], and related solid solutions were synthesized using the organic–inorganic steric entrapment method. The samples were characterized by in-situ high-temperature X-ray diffraction from 25 to 1500 C at the Advanced Photon Source and National Synchrotron Light Source II. The average linear thermal expansion of SrZr4P6O24 and CaZr4P6O24 was between  1  x 10 -6 per  °C and 6  x 10 -6 per  °C from 25 to 1500 °C. The crystal structures of the high-temperature polymorphs of CaZr4P6O24 and SrZr4P6O24 with R3c symmetry were solved by Fourier difference mapping and Rietveld refinement. This polymorph is present above  1250 °C. This work measured thermal expansion coefficients to 1500 °C for all samples and investigated the differences in thermal expansion mechanisms between polymorphs and between compositions. 
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    Free, publicly-accessible full text available February 18, 2025
  2. Tatsuki Ohji, Ph. D. Editor (Ed.)
    ZrW2O8 (ZrO2•2WO3) and HfW2O8 (HfO2•2WO3) have been the focus of thermal expansion studies due to their isotropic negative thermal expansion (NTE) measured previously at temperatures below 775◦C. This work presents measurements of these materials at their thermodynamically stable temperature ranges of 1105 and 1257◦C for ZrW2O8 and 1105–1276◦C for HfW2O8, where they were characterized with in situ, powder X-ray diffraction. The linear coefficients of thermal expansion were measured to be −5.52 × 10−6 and −4.87 × 10−6◦C−1 for ZrW2O8 and HfW2O8, respectively. The mechanism leading to this NTE is discussed. Powder samples were synthesized by a solution-based process called the organic–inorganic steric entrapment method. In situ characterization in air was carried out at the National Synchrotron Light Source II using a hexapole lamp, optical furnace and theAdvanced Photon Source using a quadrupole lamp, optical furnace to achieve elevated temperatures. 
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    Free, publicly-accessible full text available January 7, 2025
  3. Edited by H. Brand, Australian Synchrotron (Ed.)
    In the article by Hulbert & Kriven (2023), there is an error in Fig. 2(b) which shows the Bragg–Brentano geometry for an X-ray diffraction (XRD) experiment. The arc denoting the angle 2θ + δ was mistakenly drawn so that it ended at the base of the specimen. However, it should extend to the incident beam. The revised Fig. 2(b) diagram is given here, shown in Fig. 1. Both the derived equation and the conclusions in the original article are unaffected by this figure correction. 
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  4. The effect of small changes in the specimen-to-detector distance on the unit-cell parameters is examined for synchrotron powder diffraction in Debye–Scherrer (transmission) geometry with a flat area detector. An analytical correction equation is proposed to fix the shift in 2θ values due to specimen capillary displacement. This equation does not require the use of an internal reference material, is applied during the Rietveld refinement step, and is analogous to the specimen-displacement correction equations for Bragg–Brentano and curved-detector Debye–Scherrer geometry experiments, but has a different functional form. The 2θ correction equation is compared with another specimen-displacement correction based on the use of an internal reference material in which new integration and calibration parameters of area-detector images are determined. Example data sets showing the effect of a 3.3 mm specimen displacement on the unit-cell parameters for 25°C CeO 2 , including both types of displacement correction, are described. These experiments were performed at powder X-ray diffraction beamlines at the National Synchrotron Light Source II at Brookhaven National Laboratory and the Advanced Photon Source at Argonne National Laboratory. 
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  5. Characterization of the thermal expansion in the rare earth di-titanates is important for their use in high-temperature structural and dielectric applications. Powder samples of the rare earth di-titanates R 2 Ti 2 O 7 (or R 2 O 3 ·2TiO 2 ), where R = La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Y, which crystallize in either the monoclinic or cubic phases, were synthesized for the first time by the solution-based steric entrapment method. The three-dimensional thermal expansions of these polycrystalline powder samples were measured by in situ synchrotron powder diffraction from 25°C to 1600°C in air, nearly 600°C higher than other in situ thermal expansion studies. The high temperatures in synchrotron experiments were achieved with a quadrupole lamp furnace. Neutron powder diffraction measured the monoclinic phases from 25°C to 1150°C. The La 2 Ti 2 O 7 member of the rare earth di-titanates undergoes a monoclinic to orthorhombic displacive transition on heating, as shown by synchrotron diffraction in air at 885°C (864°C–904°C) and neutron diffraction at 874°C (841°C–894°C). 
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