You will be shown an abstract from a materials science research paper. Your task is to extract all synthesis operations described in the abstract into a structured JSON format. Your output should be a JSON array. Each entry in the array should be a JSON object describing a single synthesis operation. This object should have the following fields:

- "trigger": A verbal predicate indicating a synthesis operation. This should be a string extracted directly from the abstract.
- "arguments": An array of arguments specifying aspects of the synthesis operation. Each entry in the array should be a length-2 array formatted as [<argument_text>, <argument_type>]. The `argument_text` should be a string extracted directly from the abstract. The `argument_type` should be one of the following types: ["Recipe_Precursor", "Atmospheric_Material", "Participant_Material", "Recipe_Target", "Solvent_Material"].

For instance, suppose an excerpt from the abstract reads:

Tetraethoxysilane (TEOS, 98%) and cetyltrimethylammonium bromide (CTAB, 98%) were purchased from Fluka. The MTTZ-siloxy derivative (triethoxysilyl-propyl-5-mercapto-1-methyl-tetrazole) was synthesized as previously described [38].

This excerpt includes two operations, which could be annotated as follows.

[{"arguments": [["Tetraethoxysilane", "Recipe_Precursor"], ["cetyltrimethylammonium bromide", "Recipe_Precursor"]], "trigger": "purchased"}, {"arguments": [["MTTZ-siloxy derivative", "Recipe_Target"]], "trigger": "synthesized"}]

In your response, please include the JSON and no other text.

Abstract:
10.1016/j.nanoen.2016.05.050
NaV3(PO4)3/C nanocomposite as novel anode material for Na-ion batteries with high stability

NaV3(PO4)3/C was synthesized by a sol-gel process and followed by carbon thermal reduction synthesis. Typically, 6 mmol NH4VO3 were added to 70 mL deionized water maintaining at 80 degC with continuous stirring to obtain a clear yellow solution, and then 6 mmol NH4H2PO4, 2 mmol Na2CO3 and 4 mmol citric acid were added. Continuous stirring, the colour of the solution transformed to blue. After evaporation of water at 80 degC, the solution transforms from sol to gel. The gel was dried in an oven at 150 degC for 4 h, and heat-treated at 400 degC for 5 h under nitrogen atmosphere to remove CO2, H2O, and NH3. Afterward, the powder was grounded and annealed at 900 degC under H2/Ar flow (10% H2) for 12 h to produce the final compound. Herein, citric acid was used as complexing agent and carbon source. For comparison, NaV3(PO4)3 without carbon source was synthesized with the same process above. For preparing NASICON-typed Na3V2(PO4)3 cathode material, the same synthesis approach was adapted only changing the stoichiometric amount of precursor of NH4VO3, NH4H2PO4 and Na2CO3.
[{"arguments": [["NaV3(PO4)3/C", "Recipe_Target"]], "trigger": "synthesized"}, {"arguments": [["NH4VO3", "Recipe_Precursor"], ["water", "Solvent_Material"]], "trigger": "added"}, {"arguments": [["Na2CO3", "Recipe_Precursor"], ["NH4H2PO4", "Recipe_Precursor"], ["citric acid", "Participant_Material"]], "trigger": "added"}, {"arguments": [["gel", "Participant_Material"]], "trigger": "dried"}, {"arguments": [["nitrogen", "Atmospheric_Material"]], "trigger": "heat-treated"}, {"arguments": [["powder", "Participant_Material"]], "trigger": "grounded"}, {"arguments": [["H2/Ar", "Atmospheric_Material"]], "trigger": "annealed"}]