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(Na, Zr) and (Ca, Zr) Phosphate-Molybdates and Phosphate-Tungstates: I-Synthesis, Sintering and Characterization
Ist Teil von
Materials, 2023-01, Vol.16 (3), p.990
Ort / Verlag
Switzerland: MDPI AG
Erscheinungsjahr
2023
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
Submicron-grade powders of Na
Zr
(PO
)
(XO
)
compounds (hereafter referred to as NZP) and Ca
Zr
(PO
)
(XO
)
compounds (hereafter, CZP), X = Mo, W (0 ≤ x ≤ 0.5) were obtained by sol-gel synthesis. The compounds obtained were studied by X-ray diffraction phase analysis and electron microscopy. An increase in the W or Mo contents was shown to result in an increase in the unit cell volume of the NZP and CZP crystal lattices and in a decrease in the coherent scattering region sizes. Thermal expansion behavior at high temperatures of synthesized NZP and CZP compounds has been investigated. The dependencies of the parameters
and
on the heating temperature, as well as the temperature dependence of the crystal lattice unit cell volume
in the range from the room temperature up to 800 °C, were obtained. The dependencies of the average thermal expansion coefficient (α
) and of the volume coefficient (β) on the W and Mo contents in the compositions of NZP and CZP compounds were studied. Ceramics Na
Zr
(PO
)
(XO
)
with relatively high density (more than 97.5%) were produced by spark plasma sintering (SPS). The increase in the W or Mo contents in the ceramics leads to an increase in the relative density of NZP and to a decrease of the optimum sintering temperature. The mean grain size in the NZP ceramics decreases with increasing W or Mo contents. The study of strength characteristics has revealed that the hardness of the NZP ceramics is greater than 5 GPa, and that the minimum fracture toughness factor was 1 MPa·m
.