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Rapid and direct synthesis of complex perovskite oxides through a highly energetic planetary milling

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ABSTRACT

The search for a new and facile synthetic route that is simple, economical and environmentally safe is one of the most challenging issues related to the synthesis of functional complex oxides. Herein, we report the expeditious synthesis of single-phase perovskite oxides by a high-rate mechanochemical reaction, which is generally difficult through conventional milling methods. With the help of a highly energetic planetary ball mill, lead-free piezoelectric perovskite oxides of (Bi, Na)TiO3, (K, Na)NbO3 and their modified complex compositions were directly synthesized with low contamination. The reaction time necessary to fully convert the micron-sized reactant powder mixture into a single-phase perovskite structure was markedly short at only 30–40 min regardless of the chemical composition. The cumulative kinetic energy required to overtake the activation period necessary for predominant formation of perovskite products was ca. 387 kJ/g for (Bi, Na)TiO3 and ca. 580 kJ/g for (K, Na)NbO3. The mechanochemically derived powders, when sintered, showed piezoelectric performance capabilities comparable to those of powders obtained by conventional solid-state reaction processes. The observed mechanochemical synthetic route may lead to the realization of a rapid, one-step preparation method by which to create other promising functional oxides without time-consuming homogenization and high-temperature calcination powder procedures.

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(a) XRD patterns of the mechanochemically treated stoichiometric K2CO3-Na2CO3-Nb2O5 powder mixtures as a function of the milling time under condition number 2 (ΔEb = 421 mJ/hit, vt = 3825 s−1). (b) TEM bright-field image and selected-area diffraction pattern of the powders mechanochemically treated for 40 min.
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f2: (a) XRD patterns of the mechanochemically treated stoichiometric K2CO3-Na2CO3-Nb2O5 powder mixtures as a function of the milling time under condition number 2 (ΔEb = 421 mJ/hit, vt = 3825 s−1). (b) TEM bright-field image and selected-area diffraction pattern of the powders mechanochemically treated for 40 min.

Mentions: Figure 2a shows XRD patterns of the stoichiometric K2CO3-Na2CO3-Nb2O5 powder mixtures mechanochemically treated as a function of the milling time under condition number 2. The intensity of the Nb2O5 peaks rapidly decreased owing to the reduced crystallite size. The peaks belonging to the alkali metal carbonates of K2CO3 and Na2CO3 disappeared after a very short period of milling (5–10 min), accompanied by a slight increase of the background near their reflections, which indicated amorphization. The oxide-assisted amorphization of carbonates during milling is well known in A2CO3-Nb2O5 (A = K or/and Na) systems, for which the reconstruction of ions into a carbonato complex results in a loss of long-range periodicity of the carbonates40. After 30 min, the Nb2O5 peaks disappeared and the only phase detected was an orthorhombic KNN phase (JCPDS 01-071-0946, space group: Amm2) with a crystallite size of ca. 16.5–16.7 nm based on Scherrer’s formula. The formation of a nano-crystalline perovskite structure was further confirmed by TEM (Fig. 2b).


Rapid and direct synthesis of complex perovskite oxides through a highly energetic planetary milling
(a) XRD patterns of the mechanochemically treated stoichiometric K2CO3-Na2CO3-Nb2O5 powder mixtures as a function of the milling time under condition number 2 (ΔEb = 421 mJ/hit, vt = 3825 s−1). (b) TEM bright-field image and selected-area diffraction pattern of the powders mechanochemically treated for 40 min.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384223&req=5

f2: (a) XRD patterns of the mechanochemically treated stoichiometric K2CO3-Na2CO3-Nb2O5 powder mixtures as a function of the milling time under condition number 2 (ΔEb = 421 mJ/hit, vt = 3825 s−1). (b) TEM bright-field image and selected-area diffraction pattern of the powders mechanochemically treated for 40 min.
Mentions: Figure 2a shows XRD patterns of the stoichiometric K2CO3-Na2CO3-Nb2O5 powder mixtures mechanochemically treated as a function of the milling time under condition number 2. The intensity of the Nb2O5 peaks rapidly decreased owing to the reduced crystallite size. The peaks belonging to the alkali metal carbonates of K2CO3 and Na2CO3 disappeared after a very short period of milling (5–10 min), accompanied by a slight increase of the background near their reflections, which indicated amorphization. The oxide-assisted amorphization of carbonates during milling is well known in A2CO3-Nb2O5 (A = K or/and Na) systems, for which the reconstruction of ions into a carbonato complex results in a loss of long-range periodicity of the carbonates40. After 30 min, the Nb2O5 peaks disappeared and the only phase detected was an orthorhombic KNN phase (JCPDS 01-071-0946, space group: Amm2) with a crystallite size of ca. 16.5–16.7 nm based on Scherrer’s formula. The formation of a nano-crystalline perovskite structure was further confirmed by TEM (Fig. 2b).

View Article: PubMed Central - PubMed

ABSTRACT

The search for a new and facile synthetic route that is simple, economical and environmentally safe is one of the most challenging issues related to the synthesis of functional complex oxides. Herein, we report the expeditious synthesis of single-phase perovskite oxides by a high-rate mechanochemical reaction, which is generally difficult through conventional milling methods. With the help of a highly energetic planetary ball mill, lead-free piezoelectric perovskite oxides of (Bi, Na)TiO3, (K, Na)NbO3 and their modified complex compositions were directly synthesized with low contamination. The reaction time necessary to fully convert the micron-sized reactant powder mixture into a single-phase perovskite structure was markedly short at only 30–40 min regardless of the chemical composition. The cumulative kinetic energy required to overtake the activation period necessary for predominant formation of perovskite products was ca. 387 kJ/g for (Bi, Na)TiO3 and ca. 580 kJ/g for (K, Na)NbO3. The mechanochemically derived powders, when sintered, showed piezoelectric performance capabilities comparable to those of powders obtained by conventional solid-state reaction processes. The observed mechanochemical synthetic route may lead to the realization of a rapid, one-step preparation method by which to create other promising functional oxides without time-consuming homogenization and high-temperature calcination powder procedures.

No MeSH data available.


Related in: MedlinePlus