Composites of clay minerals mixed with sodium silicate as new inorganic flame retardants for wood have been investigated.

New langbeinite-type phosphates KPbCr 2 (PO 4 ) 3 and KPbFe 2 (PO 4 ) 3 are synthesized by solution method and characterized by powder X-ray diffraction, infrared spectra, thermogravimetric and differential thermal analysis, scanning electron microscope, and energy dispersive X-ray analysis. Rietveld refinement reveals that both of the compounds crystallize in the cubic system with P2 1 3 space group, and the calculated lattice parameters for Cr and Fe phases are 9.7332(2) and 9.8325(7) Å, respectively. The electron micrographs confirm the crystalline nature of the samples from their surface morphologies. Infrared spectra display the characteristic features of P−O and M−O vibrational bands for both of the phases. Thermal analysis of KPbCr 2 (PO 4 ) 3 and KPbFe 2 (PO 4 ) 3 indicates that they are thermally stable up to 1273 K. The axial thermal expansion is studied by high-temperature X-ray diffraction between 298 and 1073 K. The average thermal expansion coefficients of KPbCr 2 (PO 4 ) 3 and KPbFe 2 (PO 4 ) 3 are identified as 8.9 × 10 −6 and 10.8 × 10 −6 K −1 , respectively. Magnetic study reveals both of the compounds follow Curie−Weiss behavior in the higher-temperature region, and antiferromagnetic interactions are dominant.

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In the process of high‐level nuclear waste (HLW) disposal, monazite, LaPO4 is considered as one of the potential phosphate ceramics to immobilize lanthanides and actinides. HLW along with hazardous long‐lived nuclides contains elements such as Zr, Mo, etc. in higher wt%. In the current investigation, an attempt was made to introduce “Mo” into the monazite lattice. The phosphomolybdates of the formula La1−xCaxP1−yMoyO4, x, y=0.1–0.9 were synthesized by a solution route and characterized by powder X‐ray diffraction, FT‐IR, TGA/DTA, and scanning electron microscopic techniques. The phases with compositions La0.9Ca0.1P0.9Mo0.1O4, La0.8Ca0.2P0.8Mo0.2O4, and La0.7Ca0.3P0.7Mo0.3O4 were found to be crystallized in monazite structure. The composition La0.1Ca0.9P0.1Mo0.9O4 with X=Y=0.9 crystallized in the scheelite structure. The compositions indicate the immobilization of ∼4.1, 8.5, 12.9, and 42.5 at. wt% of “Mo.” With x, y=0.6, 0.5, 0.4, 0.3, and 0.2, along with the monazite phase, formation of a secondary phase LaP3O9 was observed.