Synthesis and characterization of the barium oxalates BaC₂O₄·0.5H₂O, α-BaC₂O₄ and β-BaC₂O₄

X-ray single-crystal and powder diffraction and neutron powder diffraction analysis were used to study the structure of BaC₂O₄·0.5H₂O and in situ X-ray powder diffraction was used to study the thermal decomposition of BaC₂O₄·0.5H₂O to α-BaC₂O₄.