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.jpowsour.2014.11.037
Phase composition and electrochemical performance of sodium lithium titanates as anode materials for lithium rechargeable batteries

NaxLi4-xTi6O14 (0 <= x <= 4) samples with different Na contents (x = 0, 1, 2, 3 and 4) were synthesized by a traditional solid-state method. The stoichiometric amounts of CH3COOLi*2H2O (Aladdin Chemistry), CH3COONa*3H2O (Aladdin Chemistry), TiO2 (Aladdin Chemistry) were mixed with oxalic acid dehydrate chelating agent (Aladdin Chemistry) under various Na/Li molar ratios and pretreated by high energy ball-milling in ethanol at 400 rpm rotational speed for 15 h. The obtained precursor slurry was dried at 80 degC and then calcinated at 900 degC for 10 h in air atmosphere. Based on the different Na/Li molar ratios, the as-prepared five NaxLi4-xTi6O14 (0 <= x <= 4) samples were designated as Li4Ti6O14, NaLi3Ti6O14, Na2Li2Ti6O14, Na3LiTi6O14 and Na4Ti6O14, respectively.
[{"arguments": [["Na", "Participant_Material"], ["NaxLi4-xTi6O14", "Recipe_Target"]], "trigger": "synthesized"}, {"arguments": [["oxalic acid dehydrate", "Participant_Material"], ["CH3COONa*3H2O", "Recipe_Precursor"], ["CH3COOLi*2H2O", "Recipe_Precursor"], ["TiO2", "Recipe_Precursor"]], "trigger": "mixed"}, {"arguments": [["ethanol", "Solvent_Material"]], "trigger": "high energy ball-milling"}, {"arguments": [["slurry", "Participant_Material"]], "trigger": "dried"}, {"arguments": [["air", "Atmospheric_Material"]], "trigger": "calcinated"}]