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.ssc.2007.04.044
Influence of Ni doping on the properties of perovskite molybdates SrMo1-xNixO3 (0.02<=x<=0.08)

A series of polycrystalline samples of SrMo1-xNixO4(0.02<=x<=0.08) were prepared through the conventional solid-state reaction method in air. Appropriate proportions of high-purity SrCO3, MoO3, and Ni powders were thoroughly mixed according to the desired stoichiometry, and then prefired at 900 [?]C for 24 h. The obtained powders were ground, pelletized, and calcined at 1000, 1100 and 1200 [?]C for 24 h with intermediate grinding twice. White compounds, SrMo1-xNixO4, were obtained. The compounds were ground and pressed into small pellets about 10 mm diameter and 2 mm thickness. These pellets were reduced in a H2/Ar (5%: 95%) flow at 920 [?]C for 12 h, and then the deep red colored products of SrMo1-xNixO3 were obtained.
[{"arguments": [["air", "Atmospheric_Material"], ["SrMo1-xNixO4", "Recipe_Target"]], "trigger": "prepared"}, {"arguments": [["SrCO3", "Recipe_Precursor"], ["MoO3", "Recipe_Precursor"], ["Ni", "Recipe_Precursor"]], "trigger": "mixed"}, {"arguments": [["powders", "Participant_Material"]], "trigger": "ground"}, {"arguments": [["SrMo1-xNixO4", "Participant_Material"]], "trigger": "obtained"}, {"arguments": [["compounds", "Participant_Material"]], "trigger": "ground"}, {"arguments": [["pellets", "Participant_Material"]], "trigger": "pressed"}, {"arguments": [["H2/Ar", "Atmospheric_Material"], ["pellets", "Participant_Material"]], "trigger": "reduced"}, {"arguments": [["SrMo1-xNixO3", "Recipe_Target"]], "trigger": "obtained"}]