diff --git a/emmet-api/emmet/api/routes/materials/thermo/query_operators.py b/emmet-api/emmet/api/routes/materials/thermo/query_operators.py
index 24a3a21ab4..ea05c2ce49 100644
--- a/emmet-api/emmet/api/routes/materials/thermo/query_operators.py
+++ b/emmet-api/emmet/api/routes/materials/thermo/query_operators.py
@@ -75,3 +75,31 @@ def query(
                 crit.update({"thermo_type": {"$in": thermo_type_list}})
 
         return {"criteria": crit}
+
+
+class MultiPhaseDiagramIDQuery(QueryOperator):
+    """
+    Method to generate a query for different root-level phase_diagram_id values
+    """
+
+    def query(
+        self,
+        phase_diagram_ids: Optional[str] = Query(
+            None,
+            description="Comma-separated list of phase_diagram_id values to query on",
+        ),
+    ) -> STORE_PARAMS:
+        crit = {}  # type: dict
+
+        if phase_diagram_ids:
+            phase_diagram_id_list = [
+                phase_diagram_id.strip()
+                for phase_diagram_id in phase_diagram_ids.split(",")
+            ]
+
+            if len(phase_diagram_id_list) == 1:
+                crit.update({"phase_diagram_id": phase_diagram_id_list[0]})
+            else:
+                crit.update({"phase_diagram_id": {"$in": phase_diagram_id_list}})
+
+        return {"criteria": crit}
diff --git a/emmet-api/emmet/api/routes/materials/thermo/resources.py b/emmet-api/emmet/api/routes/materials/thermo/resources.py
index 676c71f6ca..e714153539 100644
--- a/emmet-api/emmet/api/routes/materials/thermo/resources.py
+++ b/emmet-api/emmet/api/routes/materials/thermo/resources.py
@@ -11,6 +11,7 @@
     IsStableQuery,
     MultiThermoIDQuery,
     MultiThermoTypeQuery,
+    MultiPhaseDiagramIDQuery,
 )
 from emmet.api.core.global_header import GlobalHeaderProcessor
 from emmet.api.routes.materials.materials.query_operators import (
@@ -26,10 +27,16 @@ def phase_diagram_resource(phase_diagram_store):
     resource = ReadOnlyResource(
         phase_diagram_store,
         PhaseDiagramDoc,
+        query_operators=[
+            MultiPhaseDiagramIDQuery(),
+            SparseFieldsQuery(
+                ThermoDoc,
+                default_fields=["phase_diagram_id"],
+            ),
+        ],
         tags=["Materials Thermo"],
         sub_path="/thermo/phase_diagram/",
         disable_validation=True,
-        enable_default_search=False,
         header_processor=GlobalHeaderProcessor(),
         query_disk_use=False,
     )
diff --git a/emmet-core/emmet/core/dois.py b/emmet-core/emmet/core/dois.py
index 3bb06d4e35..9ed9eab3d9 100644
--- a/emmet-core/emmet/core/dois.py
+++ b/emmet-core/emmet/core/dois.py
@@ -17,7 +17,7 @@ class DOIDoc(BaseModel):
         description="Bibtex reference of the material.",
     )
 
-    task_id: Optional[str] = Field(
+    material_id: Optional[str] = Field(
         None,
         description="The Materials Project ID of the material. This comes in the form: mp-******.",
     )
diff --git a/emmet-core/emmet/core/eos.py b/emmet-core/emmet/core/eos.py
index b084b452f8..84f04a67af 100644
--- a/emmet-core/emmet/core/eos.py
+++ b/emmet-core/emmet/core/eos.py
@@ -23,7 +23,7 @@ class EOSDoc(BaseModel):
         description="Data for each type of equation of state.",
     )
 
-    task_id: Optional[str] = Field(
+    material_id: Optional[str] = Field(
         None,
         description="The Materials Project ID of the material. This comes in the form: mp-******.",
     )
diff --git a/emmet-core/emmet/core/fermi.py b/emmet-core/emmet/core/fermi.py
index 80ae606c14..f2f23898d3 100644
--- a/emmet-core/emmet/core/fermi.py
+++ b/emmet-core/emmet/core/fermi.py
@@ -22,7 +22,7 @@ class FermiDoc(BaseModel):
             Is either CBM or VBM for semiconductors, or fermi_surface for metals.",
     )
 
-    task_id: Optional[str] = Field(
+    material_id: Optional[str] = Field(
         None,
         description="The Materials Project ID of the material. This comes in the form: mp-******.",
     )
diff --git a/emmet-core/emmet/core/grain_boundary.py b/emmet-core/emmet/core/grain_boundary.py
index ada3c643d4..75013b8c0c 100644
--- a/emmet-core/emmet/core/grain_boundary.py
+++ b/emmet-core/emmet/core/grain_boundary.py
@@ -21,7 +21,7 @@ class GrainBoundaryDoc(BaseModel):
     Grain boundary energies, work of separation...
     """
 
-    task_id: Optional[str] = Field(
+    material_id: Optional[str] = Field(
         None,
         description="The Materials Project ID of the material. This comes in the form: mp-******.",
     )
diff --git a/emmet-core/emmet/core/surface_properties.py b/emmet-core/emmet/core/surface_properties.py
index fcee35d53e..d419633d0c 100644
--- a/emmet-core/emmet/core/surface_properties.py
+++ b/emmet-core/emmet/core/surface_properties.py
@@ -100,7 +100,7 @@ class SurfacePropDoc(BaseModel):
         description="Whether the entry has any reconstructed surfaces.",
     )
 
-    task_id: Optional[str] = Field(
+    material_id: Optional[str] = Field(
         None,
         description="The Materials Project ID of the material. This comes in the form: mp-******.",
     )