The high-temperature enthalpy of lutetium orthophosphate has been determined as a function of temperature in the range 432.92–1744.58 K using drop calorimetry. The present and earlier experimental...

The isobaric heat capacity of samarium orthotantalate M-SmTaO4was measured by adiabatic and differential scanning calorimetry in the range 17–1115 K. Smoothed heat capacity values were used to...

The design of new oxygen- and proton-conducting materials is of paramount importance for their possible utilization in solid oxide fuel cells. In the present work, La₂(Hf_2–xLa_x)O_7–x/2 (x = 0, 0.1) ceramics were prepared using ball milling of oxide mixtures (La₂O₃ and HfO₂) followed by high-temperature annealing at 1600 °C for 10 h in air. La₂Hf₂O₇ ceramics exhibit an ordered pyrochlore-type structure, whereas La₂(Hf_1.9La_0.1)O_6.95 has a defect pyrochlore structure type with oxygen vacancies at the 48f positions. The oxygen ion and proton conductivity of La₂(Hf_1.9La_0.1)O_6.95 “stuffed” pyrochlore ceramics was investigated by electrochemical impedance spectroscopy (two-probe AC) and four-probe DC measurements in a dry and a wet atmosphere (air and nitrogen). The use of two distinct conductivity measurement techniques ensured, for the first time, the collection of reliable data on the proton conductivity of the La₂(Hf_1.9La_0.1)O_6.95 “stuffed” hafnate pyrochlore. La₂Hf₂O₇ was found to be a dielectric in the range 400–900 °C, whereas the La₂(Hf_1.9La_0.1)O_6.95 “stuffed” pyrochlore had both oxygen ion and proton conductivities in this temperature range. The proton conductivity level was found to be equal to ~8 × 10⁻⁵ S/cm at 700 °C. Clearly, the proton conductivity of the La₂(Hf_1.9La_0.1)O_6.95 “stuffed” hafnate pyrochlore is mainly due to the hydration of oxygen vacancies at 48f positions.

— Polycrystalline praseodymium orthoniobate, PrNbO4, has been studied by high-temperature X‑ray diffraction and differential scanning calorimetry. We have determined the temperature of the...